Factoid: The blue whale is the largest mammal ever to inhabit the Earth.

Status:Endangered

Population: Estimated between 1,300 to 2,000, the population of blue whales is dangerously low.

Threats:Blue whales face threats from entanglement in fishing nets, pollution, and illegal whaling.

Survival:The lifespan of a blue whale is estimated to be 80 years.

Blue whales are found throughout the world's oceans. These gentle giants have grayish-blue skin with light spots. Measuring 70 to 80 feet in length (the longest recorded length was 106 feet), blue whales can weigh as much as 90 to 150 tons, although females are larger than the males.

Blue whales generally spend winters in temperate and subtropical zones, migrating toward the polar regions in spring and summer. They swim 14 miles per hour (with bursts as fast as 30 mph) and feed at depths of less than 330 feet (but can dive as deep as 1,640 feet). Dives last from 10 to 20 minutes. Usually they travel alone or in small groups of two to four, although off the coast of California some groups as large as 60 have been seen.

Blue whales have about 300 to 400 baleen plates instead of teeth which they use to strain food from the ocean water. A blue whale can eat up to 7,715 pounds of krill (small shrimp-like organisms) per day!

Blue whales were once considered too difficult to hunt because of their speed and tremendous size. However, with the introduction of factory ships and the harpoon gun in the 1920s, blue whales were hunted intensively. By the 1960s they were nearly extinct.