Throughout their range, blue whales feed predominantly on small shrimp-like crustaceans called krill. While the species of krill may differ from one ocean basin to another, the manner in which the whales feed is the same:  usually lunge feeding  through large swarms of prey, either by coming up directly underneath them with open mouths and throat pleats expanded, or by swimming on their sides with open mouths.  While doing this, blue whales can engulf more than 100 tons of water and krill, then close their mouths and contract their throat pleats, thus forcing water out of their mouths and straining the krill through their baleen plates. 

Antarctic blue whales are generally larger than other blue whale subspecies. For example, in the North Atlantic and North Pacific, blue whales can grow up to about 90 feet and are over 100,000 pounds, but in the Antarctic, they can reach up to about 110 feet and weigh more than 330,000 pounds.

• The megalodon was the largest shark to have lived, but how does it measure up to the blue whale? There's no doubt that the megalodon was huge. In fact, researchers estimate that they were at least 20 times bigger than the great whites of today, with the potential to be 50 times larger. Being 50 times bigger than a 5,000-pound shark has ensured that the megalodon will also be considered one of the largest animals ever.

Getting a true comparison with such large numbers can be difficult though.

• Since the megalodon has been extinct for millions of years, it can be difficult to get an exact average of how long they are. However, most scientists believe that they could grow to be over 50 feet long, with the longest estimates stretching up to 67 feet. This means that the megalodon is between a school bus and “Uhaul moving truck” shorter than the blue whale.

Before whalers discovered the treasure trove of oil that a blue whale could provide, the species was plentiful. But with the advent of 20th-century whaling fleets, their population plummeted until finally receiving worldwide protection in 1967. From 1904 to 1967, more than 350,000 blue whales were killed in the Southern Hemisphere, according to the World Wildlife Fund.

• Their Future Remains Uncertain

While commercial whaling is no longer a threat, recovery has been slow and new threats plague blue whales, like ship strikes and the impact of climate change. There is one population of around 2,000 blue whales off the coast of California, but all told there are only around 10,000 to 25,000 individuals left.