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A comprehensive suite of e-learning resources designed for all ages and abilities with articles, videos, educator tools, eBooks, research guides and more.

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Malala Yousafzai - Document - Gale In Context: Middle School

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Muhammad Ali - Document - Gale In Context: Middle School

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Editors: K. Lee Lerner , Brenda Wilmoth Lerner , and Kathleen J. Edgar Date: 2015

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Space Race - Document - Gale In Context: Middle School

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A comprehensive suite of e-learning resources designed for all ages and abilities with articles, videos, educator tools, eBooks, research guides and more.

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A comprehensive suite of e-learning resources designed for all ages and abilities with articles, videos, educator tools, eBooks, research guides and more.

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Nelson Mandela - Document - Gale In Context: Middle School

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During an avalanche, a mass of snow, rock, ice, soil, and other material slides swiftly down a mountainside. Avalanches of rocks or soil are often called landslides. Snowslides, the most common kind of avalanche, can sweep downhill faster than the fastest skier.

A snow avalanche begins when an unstable mass of snow breaks away from a slope. The snow picks up speed as it moves downhill, producing a river of snow and a cloud of icy particles that rises high into the air. The moving mass picks up even more snow as it rushes downhill. A large, fully developed avalanche can weigh as much as a million tons. It can travel faster than 320 kilometers per hour (200 miles per hour).

Avalanches occur as layers in a snowpack slide off. A snowpack is simply layers of snow that build up in an area, such as the side of a mountain. In winter, repeated snowfalls build a snowpack dozens of meters thick. The layers vary in thickness and texture.

The bonds between the layers of a snowpack may be weak. Melted snow that refreezes may cause a slick coating of ice to form on the surface of a layer. A new snowfall may not stick to this slippery layer, and it may slide off. During spring thaw, melted snow can seep through a snowpack, making the surface of a lower layer slippery. Added weight or vibration can easily send the top layers of a snowpack hurtling downhill.

Sluffs and Slabs

There are two main types of snow avalanches-sluffs and slabs. Sluff avalanches occur when the weak layer of a snowpack is on the top. A sluff is a small slide of dry, powdery snow that moves as a formless mass. Sluffs are much less dangerous than slab avalanches.

A slab avalanche occurs when the weak layer lies lower down in a snowpack. This layer is covered with other layers of compressed snow. When the avalanche is triggered, the weak layer breaks off, pulling all the layers on top of it down the slope. These layers tumble and fall in a giant block, or slab.

Once a slab avalanche starts, the slab shatters into many separate blocks. These snow blocks break up into ever-smaller pieces. Some of the pieces rise into the air as a moving cloud of icy particles. The cloud races downhill at very high speeds.

The thickness and speed of slab avalanches make them a threat to skiers, snowboarders, mountaineers, and hikers. In the mountains of the western United States, there are about 100,000 avalanches each year. Avalanches kill more than 150 people worldwide each year. Most are snowmobilers, skiers, and snowboarders.

Avalanche Control

Storminess, temperature, wind, the steepness of the slope, terrain, vegetation, and general snowpack conditions are all factors that influence whether an avalanche happens and what type occurs.

Snow avalanches are most likely to occur after a fresh snowfall adds a new layer to a snowpack. If new snow piles up during a storm, the snowpack may become overloaded, setting off a slide.

Earthquakes can set off avalanches, but much smaller vibrations can trigger them as well. A single skier can cause enough vibrations to set off a slide. In fact, 90 percent of avalanche incidents involving people are triggered by the victim or someone in the victim's party.

Currently, scientists are not able to predict with certainty when and where avalanches will happen. However, they can estimate hazard levels by checking on the snowpack, temperature, and wind conditions.

Many ski areas employ avalanche control teams to lessen the danger by starting slides before skiers head for the slopes. At some ski areas, patrols use explosives to set off avalanches. Or they may blast hazardous slopes with a cannon to shake loose any large, new accumulations of snow.

In the high mountains of Canada and Switzerland, special military troops are in charge of avalanche control. Many Swiss mountain villages protect homes from snowslides by building large, sturdy structures to anchor snowpacks.

Dangers of an Avalanche

An avalanche is one of the most powerful events in nature. A fractured mass of snow may flow down a slope or become airborne. As a large avalanche speeds down a mountainside, it may compress the air below it, producing a powerful wind that can blow a house apart, breaking windows, splintering doors, and tearing off the roof.

Avalanches strike suddenly and can be deadly. In 1970, a massive avalanche of rocks and ice destroyed the town of Yungay, Peru, killing 18,000 people.

If you are caught in an avalanche, the first thing to do is try to get off the slab. Skiers and snowboarders can head straight downhill to gather speed, and then veer sideways out of the slide path. Snowmobilers can punch the throttle to power out of harm's way. If this is not possible, reach for a tree. As a last resort, try to "swim" up out of the snow. The human body is three times denser than avalanche debris and will sink quickly. This makes finding and rescuing avalanche victims much more difficult.

If buried in an avalanche, try to clear some space in front of you to breathe, then punch a hand skyward. Once the avalanche stops, it settles like concrete. Bodily movement is nearly impossible. Most avalanche victims are rescued, but those who aren't die of suffocation as the snow hardens and buries them.

Avalanche beacons are the most common tools to help rescuers find avalanche victims. Avalanche beacons are "beepers" that emit consistent noise when activated. Beacons can help rescuers locate a buried victim more than 80 meters (262 feet) away.

Fast Fact

Nature's Weapon
During World War I, more than 60,000 Italian and Austrian troops died in avalanches while fighting in snowy mountain passes in the Alps. More than 10,000 died in a single day on December 13, 1916. Avalanches killed more soldiers in World War I than poison gas did.

Fast Fact

Train Wreck
At the end of February 1910, a terrible blizzard struck the town of Wellington, Washington. The nine-day snowfall trapped two trains in the town's depot. On March 1, a thunderstorm unleashed an avalanche, sending a 10-foot wall of snow toward the town. The avalanche hit the train depot and sent the trains sailing 45 meters (150 feet) downhill, killing 96 people.

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During an avalanche, a mass of snow, rock, ice, soil, and other material slides swiftly down a mountainside. Avalanches of rocks or soil are often called landslides. Snowslides, the most common kind of avalanche, can sweep downhill faster than the fastest skier. A snow avalanche begins when an unstable mass of snow breaks away from a slope.

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Toss supercooled water into an updraft of air within a thundercloud and what do you get? A hailstorm!

Subjects

Earth Science, Meteorology

Image

Hail Damage to Minivan Windshield

Hail is supercooled water, which is refrozen in the atmosphere, before falling back to the ground as a sizable ice ball. Hail can cause severe damage to life and property, like this minivan windshield.

Photography by mwesselsphotography

Imagine balls of ice, some small, some the size of grapefruits, crashing to the ground in a storm. Sound like a nightmare? For people who experience these storms, it can be. Those balls of ice are hailstones, and they can damage cars, airplanes, and crops, and in some circumstances can even kill animals and people.

Hail forms from supercooled water. Supercooled water is something unique-it's water that is below its normal freezing point of 0°C (32°F) and yet remains a liquid. Scientists aren't exactly sure how this happens, but they do know that it occurs frequently in the upper atmosphere. Supercooled water will freeze when it comes in contact with something, like an ice crystal, dust particle, or raindrop. Hail is associated with high, vertical cumulonimbus clouds, the kind of clouds that produce severe thunderstorms.

Within a cumulonimbus cloud, ice particles develop from supercooled water. The particles fall toward the bottom of the cloud from the pull of gravity, but they are forced back up by powerful updrafts of air within the clouds. In the upper part of the cloud, they encounter more supercooled water, which freezes on the ice particles, adding another layer of ice to them. This happens repeatedly. In this way, the small bits of ice grow larger and larger, becoming balls of ice-hailstones. The hailstones finally become too heavy to be lofted back up to the top of the cloud and they fall to the earth.

Because of the way they form, hailstones have a layered structure, like an onion. Really large hailstones form in storm clouds with exceptionally strong updrafts.

The National Weather Service in the United States defines large hail as being at least 2.5 centimeters (one inch) in diameter. That's about the width of a quarter. This size distinction is important because hailstones this size or larger can cause damage to property, crops, and structures. It is difficult to determine the speed hailstones fall from clouds. But one estimate, from the National Severe Storms Laboratory, is that a hailstone the size of a baseball will fall at about 161 kilometers (100 miles) per hour.

Hail does significant damage to homes and crops worldwide. One of the most devastating hailstorms in U.S. history hit near Phoenix, Arizona, in October 2010. Hailstones as big as 7.6 centimeters (three inches) were reported and $2.8 billion in damage was done. The largest hailstone ever recovered in the United States was produced by a storm in the U.S. state of South Dakota in June 2010. It was 20 centimeters (8 inches) in diameter and weighed about 0.9 kilograms (two pounds).

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Director

Tyson Brown, National Geographic Society

Author

National Geographic Society

Production Managers

Gina Borgia, National Geographic Society

Jeanna Sullivan, National Geographic Society

Program Specialists

Sarah Appleton, National Geographic Society, National Geographic Society

Margot Willis, National Geographic Society

other

Last Updated

October 19, 2023

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Toss supercooled water into an updraft of air within a thundercloud and what do you get? A hailstorm!

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Drought is an extended period of unusually dry weather when there is not enough rain. The lack of precipitation can cause a variety of problems for local communities, including damage to crops and a shortage of drinking water. These effects can lead to devastating economic and social disasters, such as famine, forced migration away from drought-stricken areas, and conflict over remaining resources.

Because the full effects of a drought can develop slowly over time, impacts can be underestimated. However, drought can have drastic and long-term effects on vegetation, animals, and people. Since 1900, more than 11 million people have died and more than 2 billion people have been affected by drought. Drought is also one of the costliest weather-related disasters. Since 2014 California has lost at least 2 billion-dollars a year, due to drought.
Defining Drought
Drought is a complicated phenomenon, and can be hard to define. One difficulty is that drought means different things in different regions. A drought is defined depending on the average amount of precipitation that an area is accustomed to receiving.

Determining the start of a drought can be tricky. Unlike many natural hazards that bring about sudden and dramatic results-such as earthquakes, tornadoes, and hurricanes-the onset of a drought can be gradual and subtle. It can take weeks, months, or even years for the full effects of long-term inadequate rainfall to become apparent.

The end of a drought can also be difficult to determine. While a single rainstorm will provide short-term relief from a drought, it might take weeks or months before levels of precipitation return to normal. The start and end of a drought are often only clear in hindsight.
Causes of Drought
Most droughts occur when regular weather patterns are interrupted, causing disruption to the water cycle. Changes in atmospheric circulation patterns can cause storm tracks to be stalled for months or years. This disruption can dramatically impact amounts of precipitation that a region normally receives. Changes in wind patterns can also be disruptive to how moisture is absorbed in various regions.

La Niña is the counterpart to El Niño, when the surface water in the Pacific Ocean along the coast of South America decreases in temperature. The cooler waters affect storm patterns by contributing to drier-than-normal conditions in parts of North and South America. El Niño and La Niña both usually last about a year. The effects of La Niña on weather patterns are often more complex than El Niño. Two of the most devastating droughts in the history of the United States-the 1930s Dust Bowl and the 1988 drought in the Midwest-are associated with the effects of La Niña.
Impacts of Drought
Trees and other plants have adapted to withstand the effects of drought through various survival methods. Some plants (such as grasses) will slow their growth or turn brown to conserve water. Trees can drop their leaves earlier in the season to prevent losing water through the leaf surface. However, if drought conditions persist, much vegetation will die.

Certain plants have adapted so they can withstand long periods without water. Yuccas, for instance, have deep root systems that can seek out water with incredible efficiency. Cacti have spiny, hairy spines, spikes, or leaves that limit how much water they lose to evaporation. Mosses can withstand complete dehydration. Juniper trees can self-prune by steering water only toward the branches required for survival. Other plants only grow when there is enough water to support them. In periods of drought, their seeds can survive under the soil for years until conditions are favorable again.

However, many organisms cannot adapt to drought conditions, and the environmental effects of extended, unusual periods of low precipitation can be severe. Negative impacts include damage to habitats, loss of biodiversity, soil erosion, and an increased risk from wildfires. During the U.S. drought of 1988, rainfall in many states was 50 to 85 percent below normal. Summer thunderstorms produced lightning without rain and ignited fires in dry trees. In Yellowstone National Park 36 percent of the park was destroyed by fire.

Drought can also create significant economic and social problems. The lack of rain can result in crop loss, a decrease in land prices, and unemployment due to declines in production. As water levels in rivers and lakes fall, water-supply problems can develop. These can bring about other social problems. Many of these problems are health-related, such as lack of water, poor nutrition, and famine. Other problems include conflicts over water usage and food, and forced migration away from drought-stricken areas.

Traditional agricultural techniques allow land to "rest" by rotating crops each season and alternating areas where livestock graze. Now, with many areas in the world struggling with overpopulation and a shortage of farmland, there is often not enough arable land to support sustainable practices. Over-farming and overgrazing can lead to soil being compacted and unable to hold water. As the soil becomes drier, it is vulnerable to erosion. This process can lead to fertile land becoming desert-like, a process known as desertification. The desertification of the Sahel in North Africa is partly blamed on a prolonged drought whose effects were intensified by farming practices that result in overgrazing.
Historical Droughts
Scientists often study historical droughts to put modern-day droughts in perspective. Since our data from thermometers and rain gauges only goes back about 100 to 150 years, scientists must research paleoclimatology, the study of the atmosphere of prehistoric Earth. Scientists gather paleoclimatic data from tree rings, sediments found in lakes and oceans, ice cores, and archaeological features and artifacts. This allows scientists to extend their understanding of weather patterns for millions of years in the past.

In South America, massive migration out of the once-fertile Atacama Desert 9,500 years ago can be explained by the onset of extreme drought.

In Africa, the Sahel region experienced a dry period from 1400 to 1750 that radically altered the landscape. The water level in Lake Bosumtwi, Ghana, for instance, fell so low that an entire forest grew on the lake's edges. Today, visitors can still see the tops of trees growing out of the lake-where the water is now more than 15 meters (50 feet) deep.

What scientists have learned by looking at Earth's drought history is that periods of severe drought are a regular part of nature's cycle. As devastating as droughts in the last century have been, they are considered relatively minor compared to the severity of earlier droughts that have lasted more than a century.
Major Droughts in the Past Century
Mass migration was an indirect effect of the Dust Bowl. Farmers and their families were forced to migrate to other areas in search of work, and by 1940, 2.5 million people had fled the Great Plains. Of those, 200,000 moved to California. The influx of migrants into existing economies already strained by the Great Depression led to a rise in conflict, unemployment, and poverty.

In the 1950s, severe drought returned to the Great Plains and southwestern United States, affecting half of the continental U.S. Low rainfall and high temperatures caused the production of crops in some areas to drop nearly 50 percent. Hay became too expensive for ranchers, and they had to feed their cattle prickly pear cactus and molasses to keep them alive. By the end of the five-year drought in 1957, 244 of Texas' 254 counties had been declared federal drought disaster areas.

Droughts continue to affect the U.S. Texas has been suffering from drought since 2010, with 2011 ranking as the driest year in the state's history. A September 2012 National Geographic magazine article called Texas "The New Dust Bowl." By 2013, 99 percent of the state was dealing with drought.

Australia is also a frequent victim of drought. The last decade has been especially severe, earning it the name The Big Dry or The Millennium Drought. Much of the country was placed under water restrictions, wildfires spread in the dry weather, and the water level in some dams fell to 25 percent. In 2007, 65 percent of viable land in Australia was declared to be in a drought. The drought was officially declared over in April 2012.

Droughts that occur in the developing world can cause even greater devastation. The Sahel region in Africa, which includes eight countries, endured a series of droughts in the 1970s and 1980s where annual rainfall dropped by about 40 percent. In the early 1970s, more than 100,000 people died and millions of people were forced to migrate. Conditions continue to be critical in the area due to drought, overpopulation, failing crops, and high food prices. Drought emergencies for the region have been declared four times since 2000.

The Horn of Africa, which includes the countries of Ethiopia, Somalia, Eritrea, and Djibouti, is particularly vulnerable to droughts. Because almost 80 percent of the population is rural and depends on agriculture for food and income, famine often accompanies drought.

Struggles for the region's limited, remaining resources can lead to conflict and war. In 1984 and 1985, the Horn of Africa suffered one of the worst droughts of the 20th century. The U.N. estimates that in Ethiopia alone, 1 million people died, 1.5 million livestock died, and 8.7 million people were affected by the drought-including being hospitalized, forced to migrate, or forced to change professions. In Sudan, 1 million people died, at least 7 million livestock died, and 7.8 million people were affected.

The cycle of drought-famine-conflict has persisted in the region, with drought conditions returning every few years since 2000. In 2006, drought affected 11 million people across the Horn of Africa, and the resulting crisis killed between 50,000 and 100,000 people and affected more than 13 million.
Forecasting and Measuring Drought
Even though scientists are unable to predict how long a drought will last or how severe it will be, early warning systems and monitoring tools can minimize some of drought's damaging impacts. There are a number of tools used to monitor drought across the U.S. Due to the limitations of each system, data from different sources are often compiled to create a more comprehensive forecast.

The Palmer Drought Severity Index (PDSI), developed in 1965 by the National Weather Service, is the most commonly used drought monitor. It is a complex measurement system and an effective way to forecast long-term drought. Its limitations are that it does not provide early warnings for drought and is not as accurate for use in mountainous areas because it does not account for snow (only rain) as precipitation. The PDSI is often used by the U.S. Department of Agriculture to determine when to begin providing drought relief.

The U.S. Drought Monitor, started in 1999, is a joint effort between three U.S. government agencies-the Department of Agriculture, the Department of Commerce, and the National Oceanic and Atmospheric Administration (NOAA). The Monitor synthesizes data from academic and federal scientists into a weekly map indicating levels of dryness around the country. It is designed to be a blend of science and art that can be used as a general summary of drought conditions around the country. It is not meant to be used as a drought predictor or for detailed information about specific areas.

The Famine Early Warning System Network (FEWS NET) monitors satellite data of crops and rainfall across Africa and some parts of Central America, the Middle East, and Central Asia. Analysis of the data allows for early intervention to try to prevent drought-induced famine.
Preparing for Drought
People and governments need to adopt new practices and policies to prepare as much as possible for inevitable future droughts. Emergency spending once a crisis has begun is less effective than money spent in preparation. The Federal Emergency Management Agency (FEMA) estimates that every $1 spent in planning for a natural hazard will save $4 in the long term.

Many areas are extremely vulnerable to drought as people continue to be dependent on a steady supply of water. The U.S. Department of Agriculture recommends a series of conservation practices to help farmers prepare for drought. Some preventative measures include installing an efficient irrigation system that reduces the amount of water lost to evaporation, storing water in ditches along fields, regularly monitoring soil moisture, planting crops that are more drought-resistant, and rotating crops to allow water in the soil to increase.

In urban areas, many cities are promoting water conservation by addressing water usage habits. Some enforce water restrictions, such as limiting days when lawns and plants can be watered, and offering free high-efficiency toilets and kitchen faucets.

Some drought-ravaged cities are taking even more extreme measures to prepare for future droughts. In Australia, the city of Perth is planning for a massive wastewater-recycling program that will eventually provide up to a quarter of the city's water demands by 2060. Perth has been dealing with a decline in rainfall since the mid 1970s. The city, which is on the edge of a huge desert, is also struggling with its history of over-consumption of water. Water-hungry traditions such as planting large, lush lawns and parks will need to be addressed through conservation measures.

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Drought is an extended period of unusually dry weather when there is not enough rain.

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The temperature outside is below freezing, the winds are howling, and you can barely see the tree in your front yard. A large amount of snow has been falling for more than three hours-a blizzard is under way.

According to the National Weather Service, blizzards are snowstorms with winds higher than 35 miles an hour and visibility (meaning, how far you can see) of less than a quarter mile. Winds from a blizzard can travel over 120 miles an hour-that's faster than a cheetah, the world's fastest land animal.

These conditions can be dangerous-low visibility can cause drivers to crash on roads, and high winds can topple power lines, which means some homes will be without heat. Large amounts of snowfall can trap people inside their homes. And those stuck outside in freezing temperatures can face frostbite or hypothermia, a condition in which your body temperature becomes dangerously low.

Learn more about these dangerous winter storms-and what to do if one comes your way.

How blizzards develop

Before you can have a blizzard, you first need snow. And for snow, you need clouds.

Clouds form when part of the air becomes cold enough that water vapor, which is the gas form of water, condenses and becomes tiny water droplets that form around things like dust and sea salt. When those droplets collect more water, they fall as rain. At temperatures between about minus 40°F and 32°F, the water droplets crystallize. When enough crystals stick together, they form snowflakes and fall to the ground.

What makes a snowstorm a blizzard is strong wind. First, warm air from the Equator mixes with cold air from the Arctic. Wind forms when warm air rises over the cold air; the faster the warm air rises over the cold air, the stronger the wind becomes.

Another type of winter storm is called a ground blizzard. This is when gusty winds-often 50 to 60 miles an hour-lift up snow that's already on the ground. Both types of blizzards can cause whiteouts, a condition in which so much snow is blowing so fast that it's hard to see anything. Sometimes you can't even tell the difference between the sky and the ground!

Blizzards in the future

Blizzards occur all over the world. But because they're closer to the Arctic, places like Russia, central and northeastern Asia, northern Europe, Canada, and the northern United States experience more blizzards than other parts of the globe.

And though most blizzards occur during winter, they can happen during other seasons, too. One of the most severe blizzards in the United States-known as the Great Blizzard of '88-happened in March 1888, killing more than 400 people.

Scientists believe that as global temperatures continue to rise because of climate change, blizzards could become more extreme. A warmer atmosphere means more moisture in the air that will eventually fall as snow (or rain); many also believe that warmer temperatures will create higher winds.

How to survive a blizzard

The best way to survive a blizzard is to prepare for extreme weather. Meteorologists use certain words and phrases that will help you know when a blizzard is coming. For instance:

Wind chill factor: This is what the temperature feels like outside, even if the real temperature is higher. Blizzards usually have wind chill factors of 10°F or lower.
Winter storm outlook or watch: This means that conditions are right for a snowstorm or blizzard to form.
Winter weather advisory: This means that dangerous winter weather is happening, which could be a blizzard.

Learn more about ways you can protect your family from dangerous winter weather.
Before a blizzard:
* Ask your parents to "winterize" your house: Check that heating sources are clean and working, and make sure windows are insulated so cold air can't come in. (If they're not, apply plastic sheets on the inside.)
* If you have a fireplace, stock up on firewood or coal.
* Make sure your family has a home emergency kit: water (at least a gallon for each person per day for several days), food (non-perishable or canned items for several days), flashlight, extra batteries, first-aid kit, manual can opener, local maps, battery-powered radio, and cell phone with a backup battery.
* Charge devices like cell phones.
During a blizzard:
* Listen to local radio or news for updated weather information.
* Layer up if you lose power. Try a t-shirt under a long-sleeved shirt under a sweater under a coat. That way you can take off items if you start to sweat. (Being cold and wet will just make you colder!) Other must-haves: two pairs of socks, mittens instead of gloves, a thick scarf, and a hat.
* Drink lots of water-or hot cocoa, or tea, or whatever-to stay hydrated. You might not think you need as much liquid in the winter as you do in summer, but staying hydrated helps your body generate enough heat to maintain a healthy body temperature.
* Evacuate only if you lose power and your home becomes too cold to stay in. Try to find a shelter-like a nearby school or library-that has heat and electricity.
If you must leave your house:
* Try to travel during the day when visibility will be better.
* Load up on blankets, canned fruits, bottles of water, and warm fluids in a thermos; bring an external battery in case you need to recharge your cell phone.
* Don't forget the layers!
* If you get stuck in your car, huddle with your companions for extra warmth.
* If you're caught outside, huddle together against a tree or a rock ledge to block the wind, and do not sit down on snow. (Your non-frozen butt will thank you.) And don't eat the snow-that could dangerously lower your body temperature.
* If you or your companions show signs of hypothermia or frostbite (shivering, feeling very tired, confusion, drowsiness, memory loss, slurred speech), seek help immediately.

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Learn how these winter snowstorms form-and how you can stay safe if one blows your way.

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When you think of crustaceans, you probably think of the big lobsters in the tank at the grocery store, but did you know that rolie-polies are crustaceans too? Most crustaceans live in the sea and include animals, such as lobsters and crabs. Two types live on land - rolie polies, also known as isopods, pillbugs or sowbugs, and crayfish.

Rolie polies are covered with overlapping plates. They eat fungus and dying plants. They roll up in a ball to protect themselves. Crayfish look a little like lobsters, but they're much smaller. They live mostly in fresh water streams and rivers. They sometimes come out at night on land to look for food. They eat plants, bugs and small animals. Both rolie polies and crayfish lay eggs. The mom carries her eggs on her back until they hatch.

Fun Facts about Crustaceans for Kids

Crustaceans are arthropods. Their skeletons are on the outside of their bodies.

Crustaceans have jointed parts so they can move. They often have many legs.

Shrimp, crabs, lobsters, barnacles and hermit crabs are all crustaceans.

Crustaceans have two pairs of antennae.

Crabs and shrimp can swim. Lobsters just scuttle about on the bottom of the ocean. Barnacles stick themselves to a hard surface like a rock or a boat and never move.

Hermit crabs can't make their own shells. They hide in shells left behind by other animals.

Crustacean Vocabulary

Learn More All About Crustaceans

Watch this amazing video documentary about crustaceans:

A documentary video about the lives of crustaceans in the reef.

Crustaceans Q&A

Question: How do crustaceans breathe?

Answer: They have gills and get oxygen from the water just like fish.

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Question: Can people eat crustaceans?

Answer: People all over the world eat crustaceans. The people of the world eat over 1 million pounds of crab every year. People also eat crayfish, lobsters and shrimp. Some people are allergic to shrimp and other crustaceans. They cannot eat these foods.

Enjoyed the Easy Science for Kids Website all about Crustaceans info? Take the FREE & fun all about Crustaceans quiz and download FREE Crustaceans worksheet for kids. For lengthy info click here.

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When you think of crustaceans, you probably think of the big lobsters in the tank at the grocery store, but did you know that rolie-polies are crustaceans too? Most crustaceans live in the sea and include animals, such as lobsters and crabs.

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Pigs are mammals in the genus Sus . They include the domestic pig and its ancestor, the common Eurasian wild boar (), and other species. Pigs are in the Suidae family of even-toed ungulates. Related, but outside the genus, are the babirusa and the warthog. Pigs, like all suids, are native to the Old World.

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The kangaroo is a marsupial from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, especially the red kangaroo, antilopine kangaroo, eastern grey kangaroo, and western grey kangaroo. Kangaroos are indigenous to Australia. The Australian government estimates that 34.3 million kangaroos lived within the commercial harvest areas of Australia in 2011, up from 25.1 million one year earlier.

The largest species in the family are called "kangaroos" and the smallest are generally called "wallabies". The term "wallaroos" refers to species of an intermediate size. There is also the tree-kangaroo which inhabits the tropical rainforests of New Guinea, far northeastern Queensland and some of the islands in the region.

The kangaroo is a symbol of Australia and appears on the Australian coat of arms and on some of its currency and is used by some of Australia's well known organisations, including Qantas and the Royal Australian Air Force. The kangaroo is important to both Australian culture and the national image, and consequently there are numerous popular culture references.

Terminology

The word "kangaroo" derives from the Guugu Yimithirr word gangurru, referring to grey kangaroos. The name was first recorded as "kanguru" on 12 July 1770 in an entry in the diary of Sir Joseph Banks; this occurred at the site of modern Cooktown, on the banks of the Endeavour River, where HMS Endeavour under the command of Lieutenant James Cook was beached for almost seven weeks to repair damage sustained on the Great Barrier Reef. Cook first referred to kangaroos in his diary entry of 4 August.

Guugu Yimithirr is the language of the people of the area.

Europeans have long regarded kangaroos as strange animals. Early explorers described them as creatures that had heads like deer (without antlers), stood upright like men, and hopped like frogs. Combined with the two-headed appearance of a mother kangaroo, this led many back home to dismiss them as travellers' tales for quite some time.

The first kangaroo to be exhibited in the western world was an example shot by John Gore, an officer on Captain Cook's Endeavour in 1770. The animal was shot and its skin and skull transported back to England whereupon it was stuffed (by taxidermists who had never seen the animal before) and displayed to the general public as a curiosity. The first glimpse of a kangaroo for many 18th-century Britons was a painting by George Stubbs.

Kangaroos are often referred to as "roos". Male kangaroos are called bucks, boomers, jacks, or old men; females are does, flyers, or jills; and the young ones are joeys. The collective noun for kangaroos is a mob, troop, or court.

Background

The kangaroo is a herbivore, eating mainly grass, but some species also eat shrubs. Because of its grazing habits, the kangaroo has developed specialised teeth that are rare amongst mammals.

Kangaroos are the only large animals to use hopping as a means of locomotion. They can hop or jump as far as about three times their own height. The comfortable hopping speed for a red kangaroo is about 20-25 km/h (12-16 mph), but speeds of up to 70 km/h (43 mph) can be attained over short distances, while it can sustain a speed of 40 km/h (25 mph) for nearly 2 km (1.2 mi).

This fast and energy-efficient method of travel has evolved because of the need to regularly cover large distances in search of food and water, rather than the need to escape predators. At slow speeds, it uses its tail to form a tripod with its two forelimbs while bringing its hind feet forward. Kangaroos are adept swimmers, and often flee into waterways if threatened by a predator.

Kangaroos are marsupials because they carry their young in a special pouch on their bodies. Baby kangaroos are called joeys. Kangaroos can be dangerous because of their powerful legs. They can lean back on their tails to deliver powerful kicks.

Kinds of kangaroos

There are four living species of kangaroos:

The Red Kangaroo (Macropus rufus) is the largest marsupial anywhere in the world. The Red Kangaroo lives in the arid and semi-arid centre of Australia. A large male can be two metres (6 ft 7 in) tall and weigh 90 kg (200 lb).

The Eastern Grey Kangaroo (Macropus giganteus) is less well-known than the red (outside of Australia), but the most often seen, as its range covers the fertile eastern part of the continent.

The Western Grey Kangaroo (Macropus fuliginosus) is slightly smaller again at about 54 kg (119 lb) for a large male. It is found in the south part of Western Australia, South Australia near the coast, and the Darling River basin.

The Antilopine Kangaroo (Macropus antilopinus) is similar to the Eastern and Western Greys. Like them, it lives on the grassy plains and woodlands. It lives in large groups.

There are also about 50 other smaller macropods in the macropodidae family.

Extinct family

There was a now- extinct family of giant kangaroos, the Sthenurinae. They were adapted for browsing in woodland areas, rather than open grassland. The largest ( Procoptodon goliah) had an estimated body mass of 240 kg., which is almost three times the weight of the largest living kangaroos. They probably moved at slower speeds, since hopping was not possible. They would have moved by striding (walking). The family went extinct about 30,000 years ago.

Interaction with humans

The kangaroo has always been a very important animal for Australian Aborigines, for its meat, hide, bone, and tendon. In addition, there were important Dreaming stories and ceremonies involving the kangaroo. Aherrenge is a current kangaroo dreaming site in the Northern Territory.

Unlike many of the smaller macropods, kangaroos have fared well since European settlement. European settlers cut down forests to create vast grasslands for sheep and cattle grazing, added stock watering points in arid areas, and have substantially reduced the number of dingoes.

Kangaroos are shy and retiring by nature, and in normal circumstances present no threat to humans. In 2003, Lulu, an eastern grey which had been hand-reared, saved a farmer's life by alerting family members to his location when he was injured by a falling tree branch. She received the RSPCA Australia National Animal Valour Award on 19 May 2004.

There are very few records of kangaroos attacking humans without provocation.

Emblems and popular culture

The kangaroo is a recognisable symbol of Australia. The kangaroo and emu feature on the Australian Coat of Arms. Kangaroos have also been featured on coins, most notably the five kangaroos on the Australian one dollar coin. The Australian Made logo consists of a golden kangaroo in a green triangle to show that a product is grown or made in Australia. The kangaroo and wallaby feature predominantly in Australian sports teams names and mascots.

Kangaroos are well represented in films, television, books, toys, souvenirs and several Christmas carols. Skippy the Bush Kangaroo was the star of the popular 1960s Australian children's television series of the same name.

Historically, the kangaroo has been a source of food for indigenous Australians. Kangaroo meat is high in protein and low in fat (about 2%). Kangaroo meat is a rich source of vitamins and minerals.

Most kangaroo meat is currently sourced from wild animals as a byproduct of population control programs. Kangaroos are hunted by licensed shooters in accordance with a strict code of practice and are protected by state and federal legislation.

Kangaroo meat is exported to many countries around the world.

Images for kids

In Spanish: Canguro para niños

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Dolphins are mammals in the order Cetacea. They are part of the toothed whales. Generally, they are among the smaller whales. Most live in salt water oceans, but some live in rivers - there are oceanic dolphins and river dolphins. Dolphins are from 1.5 to 4 metres (4.5 ft to 13 ft) long. The Killer whale is the largest of the group, and can be about 8 metres (26 ft).

The name 'dolphin' comes from the Ancient Greek δελφίς ( delphis) meaning "with a womb", because it was first thought to be a fish with a womb. It is now known to be a mammal, and quite an intelligent mammal. Dolphins breathe air. A dolphin's nose is on top of its head so the dolphin can easily breathe on the surface of the water. The skin of a dolphin has no scales. It is soft and smooth. However, it is very firm, due to how much muscle they have. Dolphins use echolocation to find their food.

Parvorder Odontoceti, toothed whales

Family Platanistidae

Family Iniidae

Family Lipotidae
Baiji (or Chinese river dolphin), Lipotes vexillifer (possibly extinct, since December 2006)

Family Pontoporiidae

Family Delphinidae, oceanic dolphins

Genus Delphinus

Genus

Common bottlenose dolphin, Tursiops truncatus

Indo-Pacific bottlenose dolphin, Tursiops aduncus

Burrunan dolphin, Tursiops australis, a newly discovered species from the sea around Melbourne in September 2011.

Genus Lissodelphis

Northern right whale dolphin, Lissodelphis borealis

Southern right whale dolphin, Lissodelphis peronii

Genus Sousa

Indo-Pacific humpback dolphin, Sousa chinensis
Chinese white dolphin (the Chinese variant), Sousa chinensis chinensis

Atlantic humpback dolphin, Sousa teuszii

Genus Stenella

Genus Cephalorhynchus

Chilean dolphin, Cephalorhynchus eutropia

Commerson's dolphin, Cephalorhynchus commersonii

Haviside's dolphin, Cephalorhynchus heavisidii

Hector's dolphin, Cephalorhynchus hectori

Genus Lagenorhynchus

Atlantic white-sided dolphin, Lagenorhynchus acutus

Dusky dolphin, Lagenorhynchus obscurus

Hourglass dolphin, Lagenorhynchus cruciger

Pacific white-sided dolphin, Lagenorhynchus obliquidens

Peale's dolphin, Lagenorhynchus australis

White-beaked dolphin, Lagenorhynchus albirostris

Genus Orcaella

Australian snubfin dolphin, Orcaella heinsohni

Irrawaddy dolphin, Orcaella brevirostris

Genus Pseudorca

Genus Globicephala

Genus †Australodelphis

Six species in the family Delphinidae are commonly called "whales", but genetically are dolphins. They are sometimes called blackfish.

Dolphins have torpedo shaped bodies with generally non-flexible necks, limbs modified into flippers, non-existent external ear flaps, a tail fin, and bulbous heads. Dolphin skulls have small eye orbits, long snouts, and eyes placed on the sides of its head. Dolphins range in size from the 1.7 metres (5.6 ft) long and 50 kilograms (110 lb) Maui's dolphin to the 9.5 metres (31 ft) and 10 metric tons (11 short tons) killer whale. Overall, however, they tend to be dwarfed by other Cetartiodactyls. Several species have female-biased sexual dimorphism, with the females being larger than the males.

Dolphins have conical shape teeth, as opposed to their counterparts, porpoise's, spade-shaped teeth. These conical teeth are used to catch swift prey such as fish, squid or large mammals, such as seal.

Breathing involves expelling stale air from their blowhole, forming an upward, steamy spout, followed by inhaling fresh air into the lungs, however this only occurs in the polar regions of the oceans. Dolphins have rather small, unidentifiable spouts.

All dolphins have a thick layer of blubber, thickness varying on climate. This blubber can help with buoyancy, protection to some extent as predators would have a hard time getting through a thick layer of fat, and energy for leaner times; the primary usage for blubber is insulation from the harsh climate. Calves, generally, are born with a thin layer of blubber, which develops at different paces depending on the habitat.

Dolphins have a two-chambered stomach that is similar in structure to terrestrial carnivores. They have fundic and pyloric chambers.

Locomotion

Dolphins have two flippers on the underside toward the head, a dorsal fin and a tail fin. These flippers contain four digits. Although dolphins do not possess fully developed hind limbs, some possess discrete rudimentary appendages, which may contain feet and digits. Dolphins are fast swimmers in comparison to seals who typically cruise at 9-28 kilometres per hour (5.6-17.4 mph); the killer whale, in comparison, can travel at speeds up to 55.5 kilometres per hour (34.5 mph). The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, which means they are unable to turn their heads. River dolphins, however, have non-fused neck vertebrae and are able to turn their head up to 90°. Dolphins swim by moving their tail fin and rear body vertically, while their flippers are mainly used for steering. Some species log out of the water, which may allow them to travel faster. Their skeletal anatomy allows them to be fast swimmers. All species have a dorsal fin to prevent themselves from involuntarily spinning in the water.

Some dolphins are adapted for diving to great depths. In addition to their streamlined bodies, some can slow their heart rate to conserve oxygen. Some can also re-route blood from tissue tolerant of water pressure to the heart, brain and other organs. Their hemoglobin and myoglobin store oxygen in body tissues and they have twice the concentration of myoglobin than hemoglobin.

The dolphin ear has specific adaptations to the marine environment. In humans, the middle ear works as an impedance equalizer between the outside air's low impedance and the cochlear fluid's high impedance. In dolphins, and other marine mammals, there is no great difference between the outer and inner environments. Instead of sound passing through the outer ear to the middle ear, dolphins receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear. The dolphin ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater. Dolphins send out high frequency clicks from an organ known as a melon. This melon consists of fat, and the skull of any such creature containing a melon will have a large depression. This allows dolphins to produce biosonar for orientation. Though most dolphins do not have hair, they do have hair follicles that may perform some sensory function. Beyond locating an object, echolocation also provides the animal with an idea on an object's shape and size, though how exactly this works is not yet understood. The small hairs on the rostrum of the boto are believed to function as a tactile sense, possibly to compensate for the boto's poor eyesight.

The dolphin eye is relatively small for its size, yet they do retain a good degree of eyesight. As well as this, the eyes of a dolphin are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When dolphins surface, their lens and cornea correct the nearsightedness that results from the refraction of light; they contain both rod and cone cells, meaning they can see in both dim and bright light, but they have far more rod cells than they do cone cells. Dolphins do, however, lack short wavelength sensitive visual pigments in their cone cells indicating a more limited capacity for color vision than most mammals. Most dolphins have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a tapetum lucidum; these adaptations allow for large amounts of light to pass through the eye and, therefore, a very clear image of the surrounding area. They also have glands on the eyelids and outer corneal layer that act as protection for the cornea.

The olfactory lobes are absent in dolphins, suggesting that they have no sense of smell.

Dolphins are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether. However, some have preferences between different kinds of fish, indicating some sort of attachment to taste.

Dolphins are often regarded as one of Earth's most intelligent animals, though it is hard to say just how intelligent. Comparing species' relative intelligence is complicated by differences in sensory apparatus, response modes, and nature of cognition. Furthermore, the difficulty and expense of experimental work with large aquatic animals has so far prevented some tests and limited sample size and rigor in others. Compared to many other species, however, dolphin behavior has been studied extensively, both in captivity and in the wild. See cetacean intelligence for more details.

Social behavior

Dolphins are highly social animals, often living in pods of up to a dozen individuals, though pod sizes and structures vary greatly between species and locations. In places with a high abundance of food, pods can merge temporarily, forming a superpod; such groupings may exceed 1,000 dolphins. Membership in pods is not rigid; interchange is common. Dolphins can, however, establish strong social bonds; they will stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if needed. This altruism does not appear to be limited to their own species. The dolphin in New Zealand has been observed guiding a female Pygmy Sperm Whale together with her calf out of shallow water where they had stranded several times. They have also been seen protecting swimmers from sharks by swimming circles around the swimmers or charging the sharks to make them go away.

Dolphins communicate using a variety of clicks, whistle-like sounds and other vocalizations. Dolphins also use nonverbal communication by means of touch and posturing.

Dolphins also display culture, something long believed to be unique to humans (and possibly other primate species). In May 2005, a discovery in Australia found Indo-Pacific bottlenose dolphins ( Tursiops aduncus) teaching their young to use tools. They cover their snouts with sponges to protect them while foraging. This knowledge is mostly transferred by mothers to daughters, unlike simian primates, where knowledge is generally passed on to both sexes. Using sponges as mouth protection is a learned behavior. Another learned behavior was discovered among river dolphins in Brazil, where some male dolphins use weeds and sticks as part of a sexual display.

Forms of care-giving between fellows and even for members of different species (see Moko (dolphin)) are recorded in various species - such as trying to save weakened fellows or female pilot whales holding up dead calves for long periods.

Dolphins engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. Male dolphins engage in acts of aggression apparently for the same reasons as humans: disputes between companions and competition for females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile after losing a fight.

Male bottlenose dolphins have been known to engage in infanticide. Dolphins have also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same diet as dolphins and are therefore not competitors for food supplies. The Cornwall Wildlife Trust records about one such death a year. Possible explanations include misdirected infanticide, misdirected sexual aggression or play behaviour.

Reproduction and sexuality

Dolphins' reproductive organs are located on the underside of the body.

The gestation period varies with species; for the small Tucuxi dolphin, this period is around 11 to 12 months, while for the orca, the gestation period is around 17 months. Typically dolphins give birth to a single calf, which is, unlike most other mammals, born tail first in most cases. The age of sexual maturity varies by species and gender.

Various methods of feeding exist among and within species, some apparently exclusive to a single population. Fish and squid are the main food, but the false killer whale and the orca also feed on other marine mammals. Orcas on occasion also hunt whale species larger than themselves.

One common feeding method is herding, where a pod squeezes a school of fish into a small volume, known as a bait ball. Individual members then take turns plowing through the ball, feeding on the stunned fish. Coralling is a method where dolphins chase fish into shallow water to catch them more easily. Orcas and bottlenose dolphins have also been known to drive their prey onto a beach to feed on it, a behaviour known as beach or strand feeding. Some species also whack fish with their flukes, stunning them and sometimes knocking them out of the water.

Vocalizations

Dolphins are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: frequency modulated whistles, burst-pulsed sounds and clicks. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to the way human vocal cords function, and through burst-pulsed sounds, though the nature and extent of that ability is not known. The clicks are directional and are for echolocation, often occurring in a short series called a click train. The click rate increases when approaching an object of interest. Dolphin echolocation clicks are amongst the loudest sounds made by marine animals.

Bottlenose dolphins have been found to have signature whistles, a whistle that is unique to a specific individual. These whistles are used in order for dolphins to communicate with one another by identifying an individual. It can be seen as the dolphin equivalent of a name for humans. These signature whistles are developed during a dolphin's first year; it continues to maintain the same sound throughout its lifetime. In order to obtain each individual whistle sound, dolphins undergo vocal production learning. This consists of an experience with other dolphins that modifies the signal structure of an existing whistle sound. An auditory experience influences the whistle development of each dolphin. Dolphins are able to communicate to one another by addressing another dolphin through mimicking their whistle. The signature whistle of a male bottlenose dolphin tends to be similar to that of his mother, while the signature whistle of a female bottlenose dolphin tends to be more distinguishing. Bottlenose dolphins have a strong memory when it comes to these signature whistles, as they are able to relate to a signature whistle of an individual they have not encountered for over twenty years. Research done on signature whistle usage by other dolphin species is relatively limited. The research on other species done so far has yielded varied outcomes and inconclusive results.

Because dolphins are generally associated in groups, communication is necessary. Signal masking is when other similar sounds (conspecific sounds) interfere with the original acoustic sound. In larger groups, individual whistle sounds are less prominent. Dolphins tend to travel in pods, upon which there are groups of dolphins that range from a few to many. Although they are traveling in these pods, the dolphins do not necessarily swim right next to each other. Rather, they swim within the same general vicinity. In order to prevent losing one of their pod members, there are higher whistle rates. Because their group members were spread out, this was done in order to continue traveling together.

Jumping and playing

Dolphins frequently leap above the water surface, this being done for various reasons. When travelling, jumping can save the dolphin energy as there is less friction while in the air. This type of travel is known as porpoising. Other reasons include orientation, social displays, fighting, non-verbal communication, entertainment and attempting to dislodge parasites.

Dolphins show various types of playful behavior, often including objects, self-made bubble rings, other dolphins or other animals. When playing with objects or small animals, common behavior includes carrying the object or animal along using various parts of the body, passing it along to other members of the group or taking it from another member, or throwing it out of the water. Dolphins have also been observed harassing animals in other ways, for example by dragging birds underwater without showing any intent to eat them. Playful behaviour that involves another animal species with active participation of the other animal can also be observed however. Playful human interaction with dolphins being the most obvious example, however playful interactions have been observed in the wild with a number of other species as well, such as humpback whales and dogs.

Juvenile dolphins off the coast of Western Australia have been observed chasing, capturing, and chewing on blowfish. While some reports that the dolphins are becoming intoxicated on the tetrodotoxin in the fishes' skin, other reports have characterized this behavior as the normal curiosity and exploration of their environment in which dolphins engage.

Intelligence

Dolphins are known to teach, learn, cooperate, scheme, and grieve. The neocortex of many species is home to elongated spindle neurons that, prior to 2007, were known only in hominids.

Brain size was previously considered a major indicator of the intelligence of an animal. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks. Allometric analysis indicates that mammalian brain size scales at approximately the ⅔ or ¾ exponent of the body mass. Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an encephalization quotient that can be used as another indication of animal intelligence. Killer whales have the second largest brain mass of any animal on earth, next to the sperm whale. The brain to body mass ratio in some is second only to humans.

Self-awareness is seen, by some, to be a sign of highly developed, abstract thinking. Self-awareness, though not well-defined scientifically, is believed to be the precursor to more advanced processes like meta-cognitive reasoning (thinking about thinking) that are typical of humans. Research in this field has suggested that cetaceans, among others, possess self-awareness. The most widely used test for self-awareness in animals is the mirror test in which a temporary dye is placed on an animal's body, and the animal is then presented with a mirror; they then see if the animal shows signs of self-recognition.

Some disagree with these findings, arguing that the results of these tests are open to human interpretation and susceptible to the Clever Hans effect. This test is much less definitive than when used for primates, because primates can touch the mark or the mirror, while cetaceans cannot, making their alleged self-recognition behavior less certain. Skeptics argue that behaviors that are said to identify self-awareness resemble existing social behaviors, and so researchers could be misinterpreting self-awareness for social responses to another individual. The researchers counter-argue that the behaviors shown are evidence of self-awareness, as they are very different from normal responses to another individual. Whereas apes can merely touch the mark on themselves with their fingers, cetaceans show less definitive behavior of self-awareness; they can only twist and turn themselves to observe the mark.

In 1995, Marten and Psarakos used television to test dolphin self-awareness. They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. While this particular study has not been repeated since then, dolphins have since passed the mirror test.

Generally, dolphins sleep with only one brain hemisphere in slow-wave sleep at a time, thus maintaining enough consciousness to breathe and to watch for possible predators and other threats. Earlier sleep stages can occur simultaneously in both hemispheres. In captivity, dolphins seemingly enter a fully asleep state where both eyes are closed and there is no response to mild external stimuli. In this case, respiration is automatic; a tail kick reflex keeps the blowhole above the water if necessary. Anesthetized dolphins initially show a tail kick reflex. Though a similar state has been observed with wild sperm whales, it is not known if dolphins in the wild reach this state. The Indus river dolphin has a sleep method that is different from that of other dolphin species. Living in water with strong currents and potentially dangerous floating debris, it must swim continuously to avoid injury. As a result, this species sleeps in very short bursts which last between 4 and 60 seconds.

Natural threats

Dolphins have few natural enemies. Some species or specific populations have none, making them apex predators. For most of the smaller species of dolphins, only a few of the larger sharks, such as the bull shark, dusky shark, tiger shark and great white shark, are a potential risk, especially for calves. Some of the larger dolphin species, especially orcas (killer whales), may also prey on smaller dolphins, but this seems rare. Dolphins also suffer from a wide variety of diseases and parasites. The Cetacean morbillivirus in particular has been known to cause regional epizootics often leaving hundreds of animals of various species dead. Symptoms of infection are often a severe combination of pneumonia, encephalitis and damage to the immune system, which greatly impair the cetacean's ability to swim and stay afloat unassisted. A study at the U.S. National Marine Mammal Foundation revealed that dolphins, like humans, develop a natural form of type 2 diabetes which may lead to a better understanding of the disease and new treatments for both humans and dolphins.

Dolphins can tolerate and recover from extreme injuries such as shark bites although the exact methods used to achieve this are not known. The healing process is rapid and even very deep wounds do not cause dolphins to hemorrhage to death. Furthermore, even gaping wounds restore in such a way that the animal's body shape is restored, and infection of such large wounds seems rare.

The study, published in the journal Marine Mammal Science, suggests that at least some dolphins are up to the shark challenge with research finding that many dolphins survive attacks using everything from sophisticated combat moves to teaming up against the shark.

Human threats

Some dolphin species face an uncertain future, especially some river dolphin species such as the Amazon river dolphin, and the Ganges and Yangtze river dolphin, which are critically or seriously endangered. A 2006 survey found no individuals of the Yangtze river dolphin, which now appears to be functionally extinct.

Pesticides, heavy metals, plastics, and other industrial and agricultural pollutants that do not disintegrate rapidly in the environment concentrate in predators such as dolphins. Injuries or deaths due to collisions with boats, especially their propellers, are also common.

Various fishing methods, most notably purse seine fishing for tuna and the use of drift and gill nets, unintentionally kill many dolphins. Accidental by-catch in gill nets and incidental captures in antipredator nets that protect marine fish farms are common and pose a risk for mainly local dolphin populations. In some parts of the world, such as Taiji in Japan and the Faroe Islands, dolphins are traditionally considered food and are killed in harpoon or drive hunts. Dolphin meat is high in mercury and may thus pose a health danger to humans when consumed.

Loud underwater noises, such as those resulting from naval sonar use, live firing exercises, and certain offshore construction projects such as wind farms, may be harmful to dolphins, increasing stress, damaging hearing, and causing decompression sickness by forcing them to surface too quickly to escape the noise.

Dolphins and other smaller cetaceans are also hunted in an activity known as dolphin drive hunting. This is accomplished by driving a pod together with boats and usually into a bay or onto a beach. Their escape is prevented by closing off the route to the ocean with other boats or nets. Dolphins are hunted this way in several places around the world, including the Solomon Islands, the Faroe Islands, Peru, and Japan, the most well-known practitioner of this method. By numbers, dolphins are mostly hunted for their meat, though some end up in dolphinariums. Despite the controversial nature of the hunt resulting in international criticism, and the possible health risk that the often polluted meat causes, thousands of dolphins are caught in drive hunts each year.

Relationships with humans

In history and religion

Dolphins have long played a role in human culture. Dolphins are sometimes used as symbols, for instance in heraldry.

In Greek myths, dolphins were seen invariably as helpers of humankind. Dolphins also seem to have been important to the Minoans, judging by artistic evidence from the ruined palace at Knossos. During the 2009 excavations of a major Mycenaean city at Iklaina, a striking fragment of a wall-paintings came to light, depicting a ship with three human figures and dolphins. Dolphins are common in Greek mythology, and many coins from ancient Greece have been found which feature a man, a boy or a deity riding on the back of a dolphin. The Ancient Greeks welcomed dolphins; spotting dolphins riding in a ship's wake was considered a good omen. In both ancient and later art, Cupid is often shown riding a dolphin. A dolphin rescued the poet Arion from drowning and carried him safe to land, at Cape Matapan, a promontory forming the southernmost point of the Peloponnesus. There was a temple to Poseidon and a statue of Arion riding the dolphin.

The Greeks reimagined the Phoenician god Melqart as Melikertês (Melicertes) and made him the son of Athamas and Ino. He drowned but was transfigured as the marine deity Palaemon, while his mother became Leucothea. ( cf Ino.) At Corinth, he was so closely connected with the cult of Poseidon that the Isthmian Games, originally instituted in Poseidon's honor, came to be looked upon as the funeral games of Melicertes. Phalanthus was another legendary character brought safely to shore (in Italy) on the back of a dolphin, according to Pausanias.

Dionysus was once captured by Etruscan pirates who mistook him for a wealthy prince they could ransom. After the ship set sail Dionysus invoked his divine powers, causing vines to overgrow the ship where the mast and sails had been. He turned the oars into serpents, so terrifying the sailors that they jumped overboard, but Dionysus took pity on them and transformed them into dolphins so that they would spend their lives providing help for those in need. Dolphins were also the messengers of Poseidon and sometimes did errands for him as well. Dolphins were sacred to both Aphrodite and Apollo.

When heraldry developed in the Middle Ages, not much was known about the biology of the dolphin and it was often depicted as a sort of fish. Traditionally, the stylised dolphins in heraldry still may take after this notion, sometimes showing the dolphin skin covered with fish scales.

Dolphins are present in the coat of arms of Anguilla and the coat of arms of Romania, and the coat of arms of Barbados has a dolphin supporter. A well-known historical example of a dolphin in heraldry, was the arms for the former province of the Dauphiné in southern France, from which were derived the arms and the title of the Dauphin of France, the heir to the former throne of France (the title literally means "The Dolphin of France").

"Dolfin" was the name of an aristocratic family in the maritime Republic of Venice, whose most prominent member was the 13th Century Doge Giovanni Dolfin.

In Hindu mythology the Ganges River Dolphin is associated with Ganga, the deity of the Ganges river. The dolphin is said to be among the creatures which heralded the goddess' descent from the heavens and her mount, the Makara, is sometimes depicted as a dolphin.

The Boto, a species of river dolphin that resides in the Amazon River, are believed to be shapeshifters, or encantados, who are capable of having children with human women.

In captivity

The renewed popularity of dolphins in the 1960s resulted in the appearance of many dolphinaria around the world, making dolphins accessible to the public. Criticism and animal welfare laws forced many to close, although hundreds still exist around the world. In the United States, the best known are the SeaWorld marine mammal parks. In the Middle East the best known are Dolphin Bay at Atlantis, The Palm and the Dubai Dolphinarium.

Various species of dolphins are kept in captivity. These small cetaceans are more often than not kept in theme parks, such as SeaWorld, commonly known as a dolphinarium. Bottlenose dolphins are the most common species of dolphin kept in dolphinariums as they are relatively easy to train, have a long lifespan in captivity and have a friendly appearance. Hundreds if not thousands of bottlenose dolphins live in captivity across the world, though exact numbers are hard to determine. Other species kept in captivity are spotted dolphins, false killer whales and common dolphins, Commerson's dolphins, as well as rough-toothed dolphins, but all in much lower numbers than the bottlenose dolphin. There are also fewer than ten pilot whales, Amazon river dolphins, Risso's dolphins, spinner dolphins, or tucuxi in captivity. An unusual and very rare hybrid dolphin, known as a wolphin, is kept at the Sea Life Park in Hawaii, which is a cross between a bottlenose dolphin and a false killer whale.

Killer whales are well known for their performances in shows, but the number of orcas kept in captivity is very small, especially when compared to the number of bottlenose dolphins, with only 44 captive killer whales being held in aquaria as of 2012. The killer whale's intelligence, trainability, striking appearance, playfulness in captivity and sheer size have made it a popular exhibit at aquaria and aquatic theme parks. From 1976 to 1997, 55 whales were taken from the wild in Iceland, 19 from Japan, and three from Argentina. These figures exclude animals that died during capture. Live captures fell dramatically in the 1990s, and by 1999, about 40% of the 48 animals on display in the world were captive-born.

Organizations such as the Mote Marine Laboratory rescue and rehabilitate sick, wounded, stranded or orphaned dolphins while others, such as the Whale and Dolphin Conservation Society and Hong Kong Dolphin Conservation Society, work on dolphin conservation and welfare. India has declared the dolphin as its national aquatic animal in an attempt to protect the endangered Ganges River Dolphin. The Vikramshila Gangetic Dolphin Sanctuary has been created in the Ganges river for the protection of the animals.

Images for kids

The face of a common bottlenose dolphin

Silver stater from Tarentum c. 290 BC showing Phalanthos riding a dolphin on one side and a rider with a shield decorated with a dolphin on the other side.

SeaWorld San Diego pilot whale with trainers.

In Spanish: Delphinidae para niños

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Flamingos are types of birds. They are noisy birds and they live in big groups called flocks. Flamingos are wading birds. This means they live by water, such as lakes.

They are in the genus Phoenicopterus and family Phoenicopteridae. There are six species of flamingo. Two of species are found in Africa, Europe and Asia. The other four are found in North America and South America.

Description

Flamingos usually stand on one leg while the other is tucked beneath their body. The reason for this behaviour is not fully understood. One theory is that standing on one leg allows the birds to conserve more body heat, given that they spend a significant amount of time wading in cold water. However, the behaviour also takes place in warm water and is also observed in birds that do not typically stand in water. An alternative theory is that standing on one leg reduces the energy expenditure for producing muscular effort to stand and balance on one leg. A study on cadavers showed that the one-legged pose could be held without any muscle activity, while living flamingos demonstrate substantially less body sway in a one-legged posture. As well as standing in the water, flamingos may stamp their webbed feet in the mud to stir up food from the bottom.

Flamingos are capable flyers and flamingos in captivity often require wing clipping to prevent escape.

Young flamingos hatch with greyish reddish plumage, but adults range from light pink to bright red due to aqueous bacteria and beta-Carotene obtained from their food supply. A well-fed, healthy flamingo is more vibrantly colored and thus a more desirable mate; a white or pale flamingo, however, is usually unhealthy or malnourished. Captive flamingos are a notable exception; they may turn a pale pink if they are not fed carotene at levels comparable to the wild.

Behaviour and ecology

Flamingos filter-feed on brine shrimp and blue-green algae. Their bills are specially adapted to separate mud and silt from the food they eat, and are uniquely used upside-down. The filtering of food items is assisted by hairy structures called lamellae which line the mandibles, and the large rough-surfaced tongue. The pink or reddish color of flamingos comes from carotenoids in their diet of animal and plant plankton. These carotenoids are broken down into pigments by liver enzymes. The source of this varies by species, and affects the saturation of color. Flamingos whose sole diet is blue-green algae are darker in color compared to those who get it second hand (e.g. from animals that have digested blue-green algae).

Flamingos are very social birds; they live in colonies whose population can number in the thousands. These large colonies are believed to serve three purposes for the flamingos: avoiding predators, maximizing food intake, and using scarce suitable nesting sites more efficiently. Before breeding, flamingo colonies split into breeding groups of about 15 to 50 birds. Both males and females in these groups perform synchronized ritual displays. The members of a group stand together and display to each other by stretching their necks upwards, then uttering calls while head-flagging, and then flapping their wings. The displays do not seem to be directed towards an individual but instead occur randomly. These displays stimulate "synchronous nesting" (see below) and help pair up those birds who do not already have mates.

Flamingos form strong pair bonds although in larger colonies flamingos sometimes change mates, presumably because there are more mates to choose from. Flamingo pairs establish and defend nesting territories. They locate a suitable spot on the mudflat to build a nest (the spot is usually chosen by the female). Nest building is sometimes interrupted by another flamingo pair trying to commandeer the nesting site for their own use. Flamingos aggressively defend their nesting sites. Both the male and the female contribute to building the nest, and to defending the nest and egg. Occasional same-sex pairs have been reported.

After the chicks hatch, the only parental expense is feeding. Both the male and the female feed their chicks with a kind of crop milk, produced in glands lining the whole of the upper digestive tract (not just the crop). Production is stimulated by the hormone prolactin. The milk contains fat, protein, and red and white blood cells. (Pigeons and doves- Columbidae -also produce a crop milk (just in the glands lining the crop), which contains less fat and more protein than flamingo crop milk.)

For the first six days after the chicks hatch, the adults and chicks stay in the nesting sites. At around seven to twelve days old, the chicks begin to move out of their nests and explore their surroundings. When they are two weeks old, the chicks congregate in groups, called "microcrèches", and their parents leave them alone. After a while, the microcrèches merge into "crèches" containing thousands of chicks. Chicks that do not stay in their crèches are vulnerable to predators.

Status and conservation

In captivity

The first flamingo hatched in a European zoo was a Chilean flamingo at Zoo Basel in Switzerland in 1958. Since then, over 389 flamingos have grown up in Basel and been distributed to other zoos around the globe.

Greater, an at least 83-year-old greater flamingo, believed to be the oldest in the world, died at the Adelaide Zoo in Australia in January, 2014.

Conservation

Many flamingos that live in Kenya and Tanzania are dying. Scientists do not know why. They think it may be because of bacteria in the water.

Images for kids

Many molecular and morphological studies support a relationship between grebes and flamingos

Moche Ceramic Depicting Flamingo (200 AD) Larco Museum Collection Lima, Peru

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Flamingos are types of birds. They are noisy birds and they live in big groups called flocks. Flamingos are wading birds. This means they live by water, such as lakes. They are in the genus Phoenicopterus and family Phoenicopteridae. There are six species of flamingo. Two of species are found in Africa, Europe and Asia.

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Jellyfish are animals of the phylum Cnidaria. They are a monophyletic clade, the Medusozoa. Most of them live in the oceans, in salt water, where they eat small sea animals like plankton and little fish, and float in the sea. Only a few jellyfish live in fresh water.

They have soft bodies and long, stinging, venomous tentacles that they use to catch their prey, usually small plankton animals or small crustaceans or tiny fish. Some jellyfish hunt other jellyfish. Venom is injected by stinging cells called nematocysts. A jellyfish is 97% water.

Most jellyfish have a bell-shaped body and long tentacles at the underside of the body. Tentacles are long "arms" with special stinging cells called nematocysts. They move by contracting their bodies, but they do not have much control over where they go: most of the time, they drift with the water current. The largest type of jellyfish is the Lion's mane jellyfish, which has tentacles that can be as long as 60 meters, but most jellyfish are much smaller.

The Medusozoa are four classes of the Cnidaria:

There are many types of jellyfish. The smallest jellyfish are just a few inches across. The largest jellyfish is the Lion's mane ( Cyanea capillata), whose body can be over 3 feet (1 m) across, with much longer tentacles. Some jellyfish glow in the dark (this is called phosphorescence). Some of the most dangerous jelly fish include the box jelly (Genuses Chironex, Chiropsalmus and Carybdea) and the tiny, two-cm-across Irukandji jelly ( Carukia barnesi); the venomous sting of these jellyfish can kill a person.

Many animals eat jellyfish, including sea turtles and some fish (including the sun fish). Humans eat jellyfish too; especially in Asia jellyfish are considered a delicacy. Jellyfish spoil very quickly after they are caught. Sometimes they are dried to preserve them. There is a different process in which they are cleaned, which can take up to 40 days. They are often eaten in a kind of salad, with soy sauce or vinegar.

Most jellyfish undergo two distinct life history stages (body forms) during their life cycle. The first is the polypoid stage, when the animal takes the form of a small stalk with feeding tentacles. Very often, this polyp is attached to the sea floor, or to another hard surface; it rarely moves around. A polyp that lives that way is called sessile. In some cases, the polyp is free-floating. Polyps generally have a mouth surrounded by upward-facing tentacles. Polyps may be on their own or in groups, and some bud asexually, making more polyps. Most are very small, measured in millimeters.

In the second stage, the tiny polyps asexually produce jellyfish, each of which is known as a medusa. Tiny jellyfish swim away from the polyp and then grow and feed in the plankton. Jellyfish reproduce both sexually and asexually. Well-fed adult jellyfish spawn daily. In most species, spawning is controlled by light, so the entire population spawns at about the same time of day, often at either dusk or dawn. Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the (unprotected) eggs are fertilized and mature into new organisms.

Medusae have a radially symmetric, umbrella-shaped body called a bell, which is usually supplied with marginal tentacles that capture prey. A few species of jellyfish do not have the polyp portion of the life cycle, but go from jellyfish to the next generation of jellyfish through direct development of fertilized eggs. Jellyfish at the medusa stage usually lives only up to six months, after which it dies.

Jellyfish eat plankton and small fish, which they catch using their venomous tentacles. Jellyfish may live in symbiosis with algae. The jellyfish transports them into sunlight and get nutrients from the algae's photosynthesis. Both forms of jelly fish have small tentacles with nematocysts (stinging cells) that sting and can hurt people on contact.

A group of jellyfish is called a smack; an occurrence of many jellyfish simultaneously is sometimes called a bloom.

Images for kids

A flower hat jelly ( Olindias formosa) photographed at the Osaka Aquarium Kaiyukan

Illustration of two life stages of seven jelly species

Aurelia sp. occurs in large quantities in most of the world's coastal waters.Members of this genus are nearly identical to each other

Like many species of jellyfish, the sting of some species of Mastigias have little or no discernible effect on humans.

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Jellyfish are animals of the phylum Cnidaria. They are a monophyletic clade, the Medusozoa. Most of them live in the oceans, in salt water, where they eat small sea animals like plankton and little fish, and float in the sea. Only a few jellyfish live in fresh water.

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You probably know sea stars as starfish, the name sea stars are commonly known by. But sea stars aren't really fish. Sea stars, like sea urchins and sand dollars, do not have backbones, which makes them part of a group called invertebrates. Fish have backbones, which makes them vertebrates. Got it?

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You probably know sea stars as starfish, the name sea stars are commonly known by. But sea stars aren't really fish. Sea stars, like sea urchins and sand dollars, do not have backbones, which makes them part of a group called invertebrates. Fish have backbones, which makes them vertebrates. Got it?

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Physical Description

The electric eel has a slender, snake-like body and flattened head. Its thick, scaleless skin is generally dark gray to brown, and its underside is a yellow-orange color.

Similar to other eel shaped fish, the electric eel lacks pelvic fins. It has a small, or reduced, caudal fin and also lacks dorsal fins. Instead, an elongated anal fin helps it maneuver through the water, where it can swim forward, backward or hover, as it searches for prey.

Three specialized electric organs-the main electrical organ, the Hunter's organ and the Sachs' organ-make up about 80 percent of this fish's body. Its remaining vital organs are tightly packed within the anterior, or front, part of its body.

The electric organs create strong and weak electric charges, which are utilized for defense, hunting, communication and navigation. Stronger electric charges can be energetically exhausting for this fish. Its strongest electric pulses are produced by the main electrical organ, as well as two-thirds of the Hunter's organ. The remainder of the Hunter's organ and the Sachs' organ produce the weaker electric discharges.

Electric eels grow to lengths of 6 to 8 feet (2 to 2.5 meters).

Native Habitat

This species is widely distributed across northern South America. Its range spans across Brazil, the Guianas, Suriname, Venezuela, Colombia, Ecuador and Peru. Electric eels inhabit the quiet, slow-moving waters of ox-bow lakes, streams, pools and flooded forests of the Amazon and Orinoco Rivers, preferring side channels but also living further inland.

Both of the rivers these fish inhabit are subject to a natural fluctuation of water driven by precipitation patterns, which results in two distinct seasons: wet and dry. The two seasons bring about drastic changes in available habitat for electric eels.

During the rainy season, the rivers swell, re-connecting lakes and ponds as the forests flood. Juvenile electric eels disperse and expand into new territories. As water recedes in the dry season, large groups of fish become isolated in the pools and smaller streams that remain.

The water in these areas is poorly oxygenated, but electric eels are specially adapted to thrive in this environment. They are obligate air-breathers, which means they surface for air periodically. Their mouths are heavily vascularized with folds that increase the surface area, allowing them to breathe air, rather than trying to meet their respiration needs through gills in warm, anoxic waters.

Throughout the dry season, the electric eel is also at greater risk from predators, such as large mammals, that hunt from outside the shallow waters it inhabits. Because there is little space to retreat, the fish is often forced to defend itself.

Water efficiently conducts electricity, providing a wide surface area for the electric eel's shock to be applied. This means that an electric pulse delivered through the water may not be as painful for a large predator as one delivered outside of the water. As such, an electric eel can instead jump out of the water, sliding its body up against a partially submerged predator to directly target its shock. The eel then delivers its electric pulses in increasing voltages.

Communication

Electric eels communicate using low electric organ discharges. This electricity is produced in pulses, and the duration of a pulse is much shorter than the time that lapses between each pulse. The frequency at which weaker electric pulses are produced varies between males and females, as well as across individuals.

Electric eels can detect these signals and interpret information about other individuals in the water. They can even convey information about their sex and sexual receptivity, which is important during the breeding season.

Electric eels are not the only fish to communicate using electric organ discharges. More than 220 species of South American knifefish in the electric eel's lineage use this highly advanced method of communication and detection.

Food/Eating Habits

Adult electric eels are generalist carnivores, eating fish, crustaceans, insects and small vertebrates, such as amphibians, reptiles and mammals. Juveniles feed primarily on invertebrates, and newly hatched electric eels will eat remaining, unhatched eggs.

In addition to defense, electric eels use their shocking power to hunt. In the dark and murky waters they inhabit, prey can be difficult to spot. To aid its hunt, the electric eel has motion-sensitive hairs along its body (the lateral line system) that detect any slight pressure change in the surrounding water. When the eel suspects a prey item is nearby, it emits two rapid electric pulses, called a doublet.

This doublet affects the muscles of the prey, causing it to twitch involuntarily and alerting the electric eel to its presence. With a series of high-voltage pulses (as many as 400 per second), it then paralyzes and consumes its prey. This entire process happens so quickly that it can be difficult for the human eye to observe in detail.

Reproduction and Development

Female electric eels lay between 1,200 and 1,700 eggs during the dry season. Males construct nests made of saliva and guard the larvae until the rainy season begins. This parental care may be the result of increased food competition and potential for predation during the dry season.

More research on the reproductive cycle and behavior of electric eels is needed to determine exactly how spawning takes place. Some researchers posit that spawning occurs in successive batches throughout the dry season, while other accounts document that all eggs are deposited at once.

The average lifespan of electric eels in the wild is still unknown. In human care, males typically live 10 to 15 years, and females generally live 12 to 22 years.

Electric eels are listed as a species of least concern by the International Union for Conservation of Nature's Red List, as of 2009.

Help this Species

Organize or attend a stream, river, lake or other waterway cleanup in your area to preserve aquatic habitats for local species.

Share the story of this animal with others. Simply raising awareness about this species can contribute to its overall protection.

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Physical Description The electric eel has a slender, snake-like body and flattened head. Its thick, scaleless skin is generally dark gray to brown, and its underside is a yellow-orange color. Similar to other eel shaped fish, the electric eel lacks pelvic fins. It has a small, or reduced, caudal fin and also lacks dorsal fins.

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When an elephant drinks, it sucks as much as 2 gallons (7.5 liters) of water into its trunk at a time. Then it curls its trunk under, sticks the tip of its trunk into its mouth, and blows. Out comes the water, right down the elephant's throat.

Since African elephants live where the sun is usually blazing hot, they use their trunks to help them keep cool. First they squirt a trunkful of cool water over their bodies. Then they often follow that with a sprinkling of dust to create a protective layer of dirt on their skin. Elephants pick up and spray dust the same way they do water-with their trunks.

Elephants also use their trunks as snorkels when they wade in deep water. An elephant's trunk is controlled by many muscles. Two fingerlike parts on the tip of the trunk allow the elephant to perform delicate maneuvers such as picking a berry from the ground or plucking a single leaf off a tree. Elephants can also use its trunk to grasp an entire tree branch and pull it down to its mouth and to yank up clumps of grasses and shove the greenery into their mouths.

When an elephant gets a whiff of something interesting, it sniffs the air with its trunk raised up like a submarine periscope. If threatened, an elephant will also use its trunk to make loud trumpeting noises as a warning.

Elephants are social creatures. They sometimes hug by wrapping their trunks together in displays of greeting and affection. Elephants also use their trunks to help lift or nudge an elephant calf over an obstacle, to rescue a fellow elephant stuck in mud, or to gently raise a newborn elephant to its feet. And just as a human baby sucks its thumb, an elephant calf often sucks its trunk for comfort. One elephant can eat 300 pounds (136 kilograms) of food in one day.

People hunt elephants mainly for their ivory tusks. Adult females and young travel in herds, while adult males generally travel alone or in groups of their own.

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When an elephant drinks, it sucks as much as 2 gallons (7.5 liters) of water into its trunk at a time. Then it curls its trunk under, sticks the tip of its trunk into its mouth, and blows. Out comes the water, right down the elephant's throat.

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In 2013, at 27, farmer Jake Hubbard of Chana, Illinois, lost his left hand in an accident. Recently, a group of eighth graders at nearby Rochelle Middle School came to his aid. As part of a STEM project, they helped…

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Margaret Eloise Knight (February 14, 1838 - October 12, 1914) was an American inventor, notably of a machine to produce flat-bottomed paper bags. She has been called "the most famous 19th-century woman inventor". She founded the Eastern Paper Bag Company in 1870, creating paper bags for groceries similar in form to the ones that would be used in later generations. Knight received dozens of patents in different fields, and became a symbol for women's empowerment.

Margaret E. Knight was born in York, Maine on February 14, 1838, to Hannah Teal and James Knight. As a little girl, "Mattie," as her parents and friends nicknamed her, preferred to play with woodworking tools instead of dolls, stating that "the only things [she] wanted were a jack knife, a gimlet, and pieces of wood." She was known as a child for her kites and sleds.

Knight and her brothers, Charlie and Jim, were raised by their widowed mother; Knight's father died when she was young, after which the impoverished family moved to Manchester, New Hampshire, where employment was available in the cotton mills. Any formal education she had was limited to secondary school, as she left to work in the mills at age 12 with her siblings.

12-year-old Knight witnessed an accident at the mill in which a worker was stabbed by a steel-tipped shuttle that shot out of a mechanical loom. Within weeks she invented a safety device for the loom, which was later adopted by other Manchester mills. The device was never patented and its exact nature is unknown, though it may have been either a device to stop the loom when the shuttle thread broke or a guard to physically block a flying shuttle.

Health problems precluded Knight from continuing to work at the cotton mill. In her teens and early 20s she held several jobs, including in home repair, daguerreotype photography, engraving, and furniture upholstery.

Knight's first patent, issued in 1870, was for an "improvement in paper-feeding machines", a "pneumatic paper-feeder" with applications in printing presses and paper-folding machines; her paper bag machine would feature a three-step folding process in forming the flat bottom. At the time, many female inventors and writers concealed their gender by using only an initial instead of their given name, but Margaret E. Knight is clearly identified in this patent.

Flat-bottomed paper bag machine

Knight moved to Springfield, Massachusetts in 1867 and was hired by the Columbia Paper Bag Company. She noticed that the envelope-shaped machine-made paper bags they produced were weak and narrow, and could not stand on their bases. They were also poorly suited to bulky items, such as groceries and hardware goods. Machines for producing these envelope-style bags were the subject of three patents issued to Francis Wolle in 1852, 1855, and 1858. Flat-bottomed paper bags, which were sturdier and more useful, were expensively made by hand.

Such flat-bottomed bags were already in general use in Britain since at least the 1840s, and improvements to hand-production techniques occurred during the 1850s. For example, a patent was awarded to James Baldwin of Birmingham in 1853 for semi-mechanized apparatus to use in the making of flat-bottomed paper bags. However, thinking to more fully automate the process, in 1868 Knight invented a machine that cut, folded, and glued paper to form the flat-bottomed brown paper bags familiar to shoppers today. This machine enabled the mass manufacture of flat-bottomed bags, much increasing the speed of production.

Knight built a wooden prototype of the device, but needed a working iron model to apply for a patent. Charles Annan (or Anan), a machinist who visited the machine shop where Knight's iron model was being built, stole her design and patented it first. When Knight attempted to patent her work, she discovered Annan's patent and filed a patent interference lawsuit in the fall of 1870. Annan argued that "she could not possibly understand the mechanical complexities of the machine", possibly exploiting prejudice against women, and/or that his was a different machine (likely on the basis of details he had misremembered), and that she had not succeeded in creating a working machine. Some authors, such as Ryan Smith of the Smithsonian Magazine, state Annan argued no woman could have designed the machine, though according to Michael Abrams of the American Society of Mechanical Engineers, this is a modern exaggeration of Annan's sole argument that his was a different machine. Knight responded with copious evidence in the form of meticulous hand-drawn blueprints, journals, and models, and a number of witnesses who testified that she had been making drawings and models beginning in 1867. She spent the then-large sum of $100 (equivalent to $2,314 in 2022) per day in legal costs for the 16-day hearing, which resulted in victory. She received her patent in 1871.

For her invention of the paper bag machine, Knight was decorated by Queen Victoria of England in 1871.

With a Massachusetts business partner, Knight established the Eastern Paper Bag Company in Hartford, Connecticut. Having no interest in managing a business, she instead received royalties from the Eastern Paper Bag Company and continued to work as an inventor. She acquired a further patent in 1879 for improvements to the paper bag machine. It was also assigned to Eastern. Though Knight earned a comfortable income by her paper bag royalties, they were however capped at $25,000 and therefore ended after a time. She would continue in this pattern for the rest of her career, selling her various inventions to companies in order to live on royalties and patent sales.

Knight moved to Ashland and then Framingham, Massachusetts, working in an office in downtown Boston.

Later inventions

In the 1880s Knight designed three domestic inventions. She patented a dress and skirt shield in 1883, a clasp for robes in 1884, and a cooking spit in 1885. In the 1880s and 1890s Knight worked on machines for manufacturing shoes, receiving six patents for several machines used in cutting shoe materials. In the early 1900s Knight developed a number of components for rotary engines and motors, with patents being granted in 1902 to 1915 (after her death). Her understanding of this work was unfortunately limited by her lack of education.

Her many other inventions include two patents of 1894: a numbering machine, and a window frame and sash. In total she was granted at least 27 and possibly 30 patents, though she also invented many devices she did not patent.

Knight continued her work late into life. A 1913 article in The New York Times reported that she was "working twenty hours a day on her eighty-ninth invention."

Knight was never wealthy, though she lived more comfortably as an adult than in childhood. Knight never married and died alone on October 12, 1914, at the age of 76, leaving an estate worth only $275.05.

As a female inventor, Knight faced certain challenges and limits. It is possible that Knight's difficulties as a female inventor may have been exaggerated in modern popular culture, such as in children's books. These include the claims that Knight's inventions were disregarded because of her gender, and that Charles Anan (or Annan) argued in court that women were incapable of such inventions. It is true however that at the time Knight patented her paper bag machine, women held an extremely small fraction of patents. Today still, fewer than 10% of primary inventors are female.

An obituary described Knight as "woman Edison". Late in her life, Knight was recognized as a leader among women, her achievements held as an example by women's rights activists and suffragettes. She was profiled in several pro-suffrage newspapers and magazines alongside other women inventors as "lady Edisons". She was featured in a 1913 New York Times article, "Women Who Are Inventors," which rebutted the idea of female intellectual inferiority. The 1913 article was written in response to a certain physician's controversial opinion that women had their place in literature but were not inventive; he pointed to the few women recorded as eminent artists, composers, inventors, or even professions thought feminine, such as chefs and fashion designers. The article responded that women had been sequestered in domestic work and denied creative opportunities, and pointed to nine women inventors of the day, Knight foremost among them.

A plaque recognizing her as the "first woman awarded a U.S. patent" and holder of 87 U.S. patents hangs on the Curry Cottage at 287 Hollis St in Framingham. However, Knight was not actually the first: either Mary Kies or Hannah Slater holds that honor.

The flat-bottomed paper bag machine was Knight's most successful invention. Knight's bags differed somewhat from modern ones. They did not have accordion-folded sides like modern bags, which are therefore more compact in storage and have more defined corners; Luther Crowell patented an accordion-pleated bag in 1872. Another feature developed later was easy unfolding into a square-bottomed shape. Paper bags replaced cloth sacks, crates, and boxes for shopping, and were standard for nearly a century before being replaced by disposable plastic bags, for which a cheap manufacturing process was developed in the 1970s and 80s.

Knight was inducted into the National Inventors Hall of Fame in 2006. A scaled-down but fully functional patent model of her original bag-making machine is in the Smithsonian Museum in Washington, D.C.

Works about her

Lynn Ng Quezon: Mattie and the Machine: A Novel. Santa Monica Press, 2022. 264pp. ISBN: 978-1-59580-118-0. (Young adult novel for ages 12+.)

Emily Arnold McCully: Marvelous Mattie: How Margaret E. Knight Became an Inventor. Farrar, Straus and Giroux, 2006. 32pp. ISBN: 0-374-34810-3. (Children's book which was recognized as one of the "best feminist books for young readers, 2007," awarded by the Amelia Bloomer Project of the Feminist Task Force of the American Library Association.)

DiMeo, Nate. no. 116,842 The Memory Palace Podcast Episode 78, November 5, 2015. (Podcast detailing Margaret Knight, her early life and inventions.)

Marilyn Bailey Ogilvie: Women in science: antiquity through the nineteenth century: a biographical dictionary with annotated bibliography. 3rd ed. MIT Press, Cambridge, MA 1991, ISBN: 0-262-65038-X, p. 110 f.

Sam Maggs: Wonder Women: 25 Innovators, Inventors, and Trailblazers who Changed History, published by Quirk Books on October 24, 2016, distributed by Penguin House. (A section detailing Knight's most notable inventions and her life.)

In Spanish: Margaret Eloise Knight para niños

Continental Paper Bag Co. v. Eastern Paper Bag Co.

Francis Wolle

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Sea otters ( Enhydra lutris) are marine mammals. They live along the Pacific coast of North America. Their historic range included shallow waters of the Bering Strait. It also included Kamchatka, and as far south as Japan.

Sea otters have about 26,000 to 165,000 hairs per square centimeters of skin. They have a rich fur for which humans hunted them almost to extinction. By the time the 1911 Fur Seal Treaty gave them protection, so few sea otters remained that the fur trade had become un profitable. Sea otters eat shellfish and other invertebrates (especially clams, abalone, and sea urchins).

The otters usually carry a favourite rock in their paws or in a pouch under their forearm. They use it to smash shells open. This makes them one of the few animals that use tools. They grow to 1.0 to 1.5 m (3.3 to 4.9 ft) in length and weigh 30 kg (66 lb). Although once near extinction, they have begun to spread again, from small populations in California and Alaska. Sea otters are one of the smallest mammals in the ocean.

Description

The sea otter is one of the smallest marine mammal species, but it is the heaviest mustelid. Male sea otters usually weigh 22 to 45 kg (49 to 99 lb) and are 1.2 to 1.5 m (3 ft 11 in to 4 ft 11 in) in length, though specimens up to 54 kg (119 lb) have been recorded. Females are smaller, weighing 14 to 33 kg (31 to 73 lb) and measuring 1.0 to 1.4 m (3 ft 3 in to 4 ft 7 in) in length. For its size, the male otter's baculum is very large, massive and bent upwards, measuring 150 mm (5.9 in) in length and 15 mm (0.59 in) at the base.

Unlike most other marine mammals, the sea otter has no blubber and relies on its exceptionally thick fur to keep warm. With up to 150,000 strands of hair per square centimetre (nearly one million per sq in), its fur is the densest of any animal. The fur consists of long, waterproof guard hairs and short underfur; the guard hairs keep the dense underfur layer dry. Cold water is kept completely away from the skin and heat loss is limited. The fur is thick year-round, as it is shed and replaced gradually rather than in a distinct molting season. As the ability of the guard hairs to repel water depends on utmost cleanliness, the sea otter has the ability to reach and groom the fur on any part of its body, taking advantage of its loose skin and an unusually supple skeleton. The coloration of the pelage is usually deep brown with silver-gray speckles, but it can range from yellowish or grayish brown to almost black. In adults, the head, throat, and chest are lighter in color than the rest of the body.

The sea otter displays numerous adaptations to its marine environment. The nostrils and small ears can close. The hind feet, which provide most of its propulsion in swimming, are long, broadly flattened, and fully webbed. The fifth digit on each hind foot is longest, facilitating swimming while on its back, but making walking difficult. The tail is fairly short, thick, slightly flattened, and muscular. The front paws are short with retractable claws, with tough pads on the palms that enable gripping slippery prey. The bones show osteosclerosis, increasing their density to reduce buoyancy.

The sea otter propels itself underwater by moving the rear end of its body, including its tail and hind feet, up and down, and is capable of speeds of up to 9 km/h (5.6 mph). When underwater, its body is long and streamlined, with the short forelimbs pressed closely against the chest. When at the surface, it usually floats on its back and moves by sculling its feet and tail from side to side. At rest, all four limbs can be folded onto the torso to conserve heat, whereas on particularly hot days, the hind feet may be held underwater for cooling. The sea otter's body is highly buoyant because of its large lung capacity - about 2.5 times greater than that of similar-sized land mammals - and the air trapped in its fur. The sea otter walks with a clumsy, rolling gait on land, and can run in a bounding motion.

Long, highly sensitive whiskers and front paws help the sea otter find prey by touch when waters are dark or murky. Researchers have noted when they approach in plain view, sea otters react more rapidly when the wind is blowing towards the animals, indicating the sense of smell is more important than sight as a warning sense. Other observations indicate the sea otter's sense of sight is useful above and below the water, although not as good as that of seals. Its hearing is neither particularly acute nor poor.

An adult's 32 teeth, particularly the molars, are flattened and rounded for crushing rather than cutting food. Seals and sea otters are the only carnivores with two pairs of lower incisor teeth rather than three; the adult dental formula is . The teeth and bones are sometimes stained purple as a result of ingesting sea urchins.

The sea otter is diurnal. It has a period of foraging and eating in the morning, starting about an hour before sunrise, then rests or sleeps in mid-day. Foraging resumes for a few hours in the afternoon and subsides before sunset, and a third foraging period may occur around midnight. Females with pups appear to be more inclined to feed at night. Observations of the amount of time a sea otter must spend each day foraging range from 24 to 60%, apparently depending on the availability of food in the area.

Sea otters spend much of their time grooming, which consists of cleaning the fur, untangling knots, removing loose fur, rubbing the fur to squeeze out water and introduce air, and blowing air into the fur. To casual observers, it appears as if the animals are scratching, but they are not known to have lice or other parasites in the fur. When eating, sea otters roll in the water frequently, apparently to wash food scraps from their fur.

The sea otter hunts in short dives, often to the sea floor. Although it can hold its breath for up to five minutes, its dives typically last about one minute and not more than four. It is the only marine animal capable of lifting and turning over rocks, which it often does with its front paws when searching for prey. The sea otter may also pluck snails and other organisms from kelp and dig deep into underwater mud for clams. It is the only marine mammal that catches fish with its forepaws rather than with its teeth.

Under each foreleg, the sea otter has a loose pouch of skin that extends across the chest. In this pouch (preferentially the left one), the animal stores collected food to bring to the surface. This pouch also holds a rock, unique to the otter, that is used to break open shellfish and clams. There, the sea otter eats while floating on its back, using its forepaws to tear food apart and bring it to its mouth. It can chew and swallow small mussels with their shells, whereas large mussel shells may be twisted apart. It uses its lower incisor teeth to access the meat in shellfish. To eat large sea urchins, which are mostly covered with spines, the sea otter bites through the underside where the spines are shortest, and licks the soft contents out of the urchin's shell.

The sea otter's use of rocks when hunting and feeding makes it one of the few mammal species to use tools. To open hard shells, it may pound its prey with both paws against a rock on its chest. To pry an abalone off its rock, it hammers the abalone shell using a large stone, with observed rates of 45 blows in 15 seconds. Releasing an abalone, which can cling to rock with a force equal to 4,000 times its own body weight, requires multiple dives.

Social structure

Although each adult and independent juvenile forages alone, sea otters tend to rest together in single-sex groups called rafts. A raft typically contains 10 to 100 animals, with male rafts being larger than female ones. The largest raft ever seen contained over 2000 sea otters. To keep from drifting out to sea when resting and eating, sea otters may wrap themselves in kelp.

A male sea otter is most likely to mate if he maintains a breeding territory in an area that is also favored by females. As autumn is the peak breeding season in most areas, males typically defend their territory only from spring to autumn. During this time, males patrol the boundaries of their territories to exclude other males, although actual fighting is rare. Adult females move freely between male territories, where they outnumber adult males by an average of five to one. Males that do not have territories tend to congregate in large, male-only groups, and swim through female areas when searching for a mate.

The species exhibits a variety of vocal behaviors. The cry of a pup is often compared to that of a seagull. Females coo when they are apparently content; males may grunt instead. Distressed or frightened adults may whistle, hiss, or in extreme circumstances, scream. Although sea otters can be playful and sociable, they are not considered to be truly social animals. They spend much time alone, and each adult can meet its own needs in terms of hunting, grooming, and defense.

Reproduction and lifecycle

Births occur year-round, with peaks between May and June in northern populations and between January and March in southern populations. Gestation appears to vary from four to twelve months, as the species is capable of delayed implantation followed by four months of pregnancy. In California, sea otters usually breed every year, about twice as often as those in Alaska.

Birth usually takes place in the water and typically produces a single pup weighing 1.4 to 2.3 kg (3 to 5 lb). Twins occur in 2% of births; however, usually only one pup survives. At birth, the eyes are open, ten teeth are visible, and the pup has a thick coat of baby fur. Mothers have been observed to lick and fluff a newborn for hours; after grooming, the pup's fur retains so much air, the pup floats like a cork and cannot dive. The fluffy baby fur is replaced by adult fur after about 13 weeks.

Nursing lasts six to eight months in Californian populations and four to twelve months in Alaska, with the mother beginning to offer bits of prey at one to two months. The milk from a sea otter's two abdominal nipples is rich in fat and more similar to the milk of other marine mammals than to that of other mustelids. A pup, with guidance from its mother, practices swimming and diving for several weeks before it is able to reach the sea floor. Initially, the objects it retrieves are of little food value, such as brightly colored starfish and pebbles. Juveniles are typically independent at six to eight months, but a mother may be forced to abandon a pup if she cannot find enough food for it; at the other extreme, a pup may nurse until it is almost adult size. Pup mortality is high, particularly during an individual's first winter - by one estimate, only 25% of pups survive their first year. Pups born to experienced mothers have the highest survival rates.

Females perform all tasks of feeding and raising offspring, and have occasionally been observed caring for orphaned pups. Much has been written about the level of devotion of sea otter mothers for their pups - a mother gives her infant almost constant attention, cradling it on her chest away from the cold water and attentively grooming its fur. When foraging, she leaves her pup floating on the water, sometimes wrapped in kelp to keep it from floating away; if the pup is not sleeping, it cries loudly until she returns. Mothers have been known to carry their pups for days after the pups' deaths.

In the wild, sea otters live to a maximum age of 23 years, with average lifespans of 10-15 years for males and 15-20 years for females. Several captive individuals have lived past 20 years, and a female at the Seattle Aquarium died at the age of 28 years. Sea otters in the wild often develop worn teeth, which may account for their apparently shorter lifespans.

Images for kids

A mother floats with her pup on her chest. Georg Steller wrote, "They embrace their young with an affection that is scarcely credible."

California's remote areas of coastline sheltered small colonies of sea otters through the fur trade. The 50 that survived in California, which were rediscovered in 1938, have since reproduced to almost 3,000.

Sea otters control herbivore populations, ensuring sufficient coverage of kelp in kelp forests

Aleut men in Unalaska in 1896 used waterproof kayak gear and garments to hunt sea otters.

Sea otters off the coast of Washington, within the Olympic Coast National Marine Sanctuary

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Sea otters ( Enhydra lutris) are marine mammals. They live along the Pacific coast of North America. Their historic range included shallow waters of the Bering Strait. It also included Kamchatka, and as far south as Japan. Sea otters have about 26,000 to 165,000 hairs per square centimeters of skin.

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