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Jaguars are great swimmers. They sometimes attack crocodiles!

Jaguars can live 12 to 15 years.

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Scientific Name:

Panthera onca

Average Life Span In The Wild:

12 to 15 years

Size:

Head and body, five to six feet; tail, 27.5 to 36 inches

Weight:

100 to 250 pounds

Size relative to a 6-ft man:

What is the jaguar?

Jaguars are the only big cat in the Americas and the third biggest in the world after tigers and lions. They look a lot like leopards, which live in Africa and Asia, but jaguars' spots are more complex and often have a dot in the center.

These powerful cats were worshipped as gods in many ancient South American cultures, and representations of the jaguar show up in the art and archaeology of pre-Columbian cultures across the jaguar's range.

Diet and behavior

Unlike many other cats, jaguars do not avoid water. In fact, they are quite good swimmers. They hunt fish, turtles, and even caimans, using their incredibly powerful jaws to pierce the animals' skulls. Jaguars also eat deer, peccaries, capybaras, tapirs, and a number of other land animals, which they prefer to ambush at night.

Jaguars live alone, and they're territorial-they define their area by marking with their waste or clawing trees.

Females have litters of one to four cubs, which are blind and helpless at birth. The mother stays with them and defends them fiercely from any animal that may approach-even their own father. Young jaguars learn to hunt by living with their mothers for two years or more.

Range and habitat

Jaguars once roamed broadly from central Argentina all the way up to the southwestern United States. Since the 1880s, they've lost more than half their territory. Their main stronghold today is the Amazon Basin, though they still exist in smaller numbers through Central America as well.

They're typically found in tropical rainforests but also live in savannas and grasslands.

Threats to survival

Jaguars face a number of threats, including habitat fragmentation and illegal killing. South and Central America's high rates of deforestation- for grazing land, agriculture, and other uses -have not only destroyed jaguars' habitat but also broken it up. Fragmented forests mean that cats get boxed into patches of forest and can't travel far to find new mates. That kind of isolation can lead to inbreeding and local extinctions.

Another threat jaguars face is retaliatory killings from ranchers. As grazing land replaces forests, jaguars are more likely to hunt cattle. In response-and sometimes in anticipation-cattle owners kill jaguars.

Poaching is another growing problem for jaguars. They've long been hunted for their pelts, and now there's a growing illegal, international trade in jaguar teeth and jaguar bone products going to China.

Conservation

Jaguars are classified as near-threatened by the International Union for the Conservation of Nature. The species has national protections in almost every country it's found, and trade in its parts is banned by CITES, a global treaty that regulates the cross-border wildlife trade. Still, poaching and the illegal trade continues so strengthening law enforcement is important.

There are major efforts to support and develop jaguar corridors to connect isolated populations as well as to work with ranchers to reduce human-jaguar conflict. Workshops help ranchers learn better husbandry practices, and a growing number of programs compensate ranchers when they lose cattle to jaguars, so that they're less motivated to kill the cat in retaliation.

Fighting deforestation, which a number of international NGOs and indigenous groups are involved in, is critical.

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Scientific Name: Panthera onca Average Life Span In The Wild: 12 to 15 years Size: Head and body, five to six feet; tail, 27.5 to 36 inches Weight: 100 to 250 pounds Size relative to a 6-ft man: Jaguars are the only big cat in the Americas and the third biggest in the world after tigers and lions.

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There are about 40,000 types of spiders!

Spiders can have 6 or 8 eyes.

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(Image credit: Rick Vetter)

All spiders are predatory eight-legged creatures that have organs to spin silk at the back ends of their bodies. They are the largest part of the Arachnid family, a group that also includes scorpions and ticks. Spiders all have the ability to bite with venom-injecting fangs to kill prey and nearly all of them are poisonous (even if it's just a little).

There are about 40,000 types of spiders in the world, living on every continent except Antarctica. And they're not newbies: fossilized spiders have been found in Carboniferous rocks dating back 318 million years.

Spider anatomy

Spiders have two body segments, the abdomen and the cephalothorax. The first, or front part, is the cephalothorax, which is formed by the fusing of the head and thorax, according to Jo-Anne Nina Sewlal, an arachnologist at the University of the West Indies in Trinidad. The cephalothorax contains the eyes, mouth and legs.

The mouth has several parts. The spider's jaws, called the chelicerae, are tipped with fangs, according to entomologists at the University of Kentucky. These appendages are used to hold prey while the spider injects venom. Behind the jaws are the labium and labrum, which work together to direct food into the spider's mouth.

Between the chelicerae and the first pair of legs are the pedipalps, which look like tiny legs but are actually similar to antennae, and are used to sense objects the spider encounters, Sewlal said. However, "they are used by some species in prey capture and feeding as well as in shaping their webs."

Pedipalps are also used in mating and are a good way to tell males and females apart. "The tips in males are enlarged as they are used to transfer sperm to the female, while in the female, the tips of the pedipalps remain undifferentiated," Sewlal said.

Most spiders have six or eight eyes, according to the University of Kentucky. Some spiders can only see the difference between light and shadow. Their eyes are considered "simple," as they don't have compound lenses as some insects do.

A spider's abdomen is where most of its important internal organs are located, such as the reproductive system, lungs and digestive tract. Also on the abdomen are the spinnerets, through which a spider produces its silken web.

Spider webs

Spider silk is made of strong strands of protein. It is the strongest-known natural fiber, according to the San Diego Zoo. Its tensile strength - the greatest stress a material will tolerate before breaking - is greater than bone and half the strength of steel.

According to the Smithsonian Museum of Natural History, individual species can produce up to seven distinct types of silk, each with a specialized function. Some spiders use their webs to trap prey; others line their burrows with it.

Spiders are grouped according to the type of web they make, according to the San Diego Zoo. Groups include tangle-web spiders, orb-web spiders, funnel-web spiders and nursery-web spiders.

According to the Australian Museum, spiders capture prey using a variety of methods. They can trap small insects in sticky webs, lasso them with sticky bolas, or use their vibration-sensing skills to chase prey down. Spider guts are too narrow to take solids, so they liquidize their food by flooding it with digestive enzymes and grinding it up with short appendages.

Spider bites

Even though all spiders can bite, most of them do no more harm to a human than a bee sting or a mosquito bite. Most spiders with a life-threatening bite are quite shy and attack only when they feel threatened. According to Spider Physiology and Behaviour, Volume 41 (Advances in Insect Physiology) (opens in new tab), there were only about 100 deaths from spider bites during the 20th century.

According to Sewlal, spider venoms work on one of two fundamental principles: they either attack the nervous system with neurotoxic venom, or attack tissues around the bite with necrotic venom. Sewlal explained that neurotoxic venom works in two ways: by overstimulating "the production of the neurotransmitters ... which can cause the entire nervous system to become paralyzed," and by blocking "nerve impulses to the muscles. This has the result of causing the muscles to cramp and become rigid. It also has the effect of disrupting many bodily functions." Necrotic venom works by causing "the tissue around the bite to die."

Researchers are investigating novel uses for spider venom, from an eco-friendly (and bee-friendly) alternative to pesticides, to treatments for Alzheimer's disease, cardiac arrhythmia and strokes (opens in new tab). In addition, spider silk has lots of engineering uses, from body armor to optical communications.

Arachnophobia

Humans have long had a tumultuous relationship with the eight-legged critters. Arachnophobia, or fear of spiders, is one of the most common phobias. Some statistics show that 50 percent of women and 16 percent of men have this phobia, according to The Wall Street Journal.

According to Mentally Healthy, evolutionary biologists surmise that a modern fear of spiders may be an exaggerated form of an instinctive response that helped early humans to survive. Other scholars think that fear of spiders began in the Middle Ages, when spiders became a cultural scapegoat for inexplicable epidemics of the time, like the plague.

Classification/taxonomy

According to the Integrated Taxonomic Information System (ITIS), the taxonomy of spiders is:

(Image credit: Shane Wilson Link (opens in new tab) Shutterstock (opens in new tab))

Kingdom: Animalia

Subkingdom: Bilateria

Infrakingdom: Protostomia

Superphylum: Ecdysozoa

Phylum: Arthropoda

Subphylum: Chelicerata

Class: Arachnida

Order: Araneae

Suborders

According to Sewlal, spiders can be divided into two suborders: Mesotelae and Opisthothelae, which contains the infraorders Mygalomorphae and Araneomorphae.

Mesothelae: "The suborder Mesothelae contains only one family, Liphistiidae," Sewlal said. "The members of this family are quite distinctive from all other spiders." She explained that the Mesothelae suborder is so named because its members have their spinnerets located on the middle of the abdomen, on their underside. According to the Australian Museum, these are "primitive spiders"; "modern" spiders have spinnerets toward the back of their abdomens. They also have abdomens segmented similarly to scorpions, Sewlal said.

These small, light spiders reside in Southeast Asia, China and Japan. Though scientists previously thought they lacked venom glands, new research has shown that they do have them.

Opisthothelae: These spiders have spinnerets at the posterior of their abdomens, Sewlal said. She offered some advice on how to distinguish between the infraorders Mygalomorphae and Araneomorphae: Look at the position of the chelicerae. "Araneomorphs have chelicerae where the tips crisscross each other, while mygalomorphs have chelicerae that point downwards like that of the typical vampire and move in the vertical plane." Their book lungs - respiratory organs so named because their thin membranes resemble pages in a book - are also different. "Mygalomorph spiders also have two pairs of book lungs while araneomorph spiders have one pair of book lungs or no book lungs at all."

Here are some other features of the two infraorders.

Mygalomorphae: According to Arachne.org, these spiders are generally heavily built and hairy, like tarantulas. They live in burrows, and can prey on creatures as large as frogs, lizards and snails. A few species build webs, but it is not very common. Although most spiders live for at most two years, many mygalomorphae spiders can live up to 25 years in captivity. This type of spider includes the huge goliath birdeater, which can grow up to 1 foot in body length, according to the Conservation Institute.
Katherine Gammon contributed to this article.
Araneomorphae: These are the most common of spiders, making up more than 90 percent of all the species, according to Biology of Spiders (opens in new tab). Some of the most interesting species include the only known vegetarian spider, the Bagheera kiplingi, as well as the most venomous spider, the Brazilian wandering spider. Scientists have found that the spider needs to inject only 6 micrograms of its venom to kill a 20-gram (0.7 ounces) mouse, and a full venom load is more than 10 times that.

Editor's Note: If you'd like more information on this topic, we recommend the following book:

(opens in new tab)

Additional resources

Learn facts about these popular spiders:

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(Image credit: Rick Vetter) All spiders are predatory eight-legged creatures that have organs to spin silk at the back ends of their bodies. They are the largest part of the Arachnid family, a group that also includes scorpions and ticks.