They feed in high latitudes and migrate to the tropics to breed and give birth. Worldwide blue whale population is unknown however, blue whales are considered endangered according to the U.S. Endangered Species Act . Blue whales were hunted extensively for their large quantities of baleen, blubber, and meat. Although blue whales are protected, their populations show few signs of recovery. Female blue whales are generally larger than males, and northern hemisphere blue whales are generally smaller than those in the southern hemisphere.
Blue whales are light bluish gray on their dorsal side and mottled gray whitish on their bellies.
Some have yellowish bellies. It is hard to know the answer to this question since blue whales are so big and live in the open ocean. Blue whales filter their food through their baleen plates. A blue whale can eat up to 8,000 lbs. of krill during its peak consumption period. It is estimated to take 2,200 lbs. of food to fill a blue whale's stomach.