According to National Geographic, the blue whale, a mammal, grows up to 100 feet in length and can weigh over 200 tons. It's the largest animal ever known to exist. Despite its enormous size, the blue whale's diet consists almost entirely of tiny crustaceans called krill.
The blue whale is found in all oceans of the world, spending the summertime near the poles and in winter swimming to the equator. Blue whales communicate through pulses, groans and moans, able to be heard by other whales at a distance of up to 1,000 miles. An endangered species, the blue whale's future is compromised by the hunting done by man in the early-to-mid 20th century.