Description & Characteristics:
Largest of Earth’s animals, the majestic Blue whale can be found in all the world’s oceans. In summer, they frequent the fringes of the polar ice shelves, moving to tropical and subtropical waters during the winter months. They travel alone or occasionally in pairs, with the larger individuals occuring the farthest south. Once numbering close to 200,000 individuals, Blue whales were heavily exploited for their oil, meat, and baleen during the early to mid 1900’s, severely reducing the species’ population to near the point of extinction. Since the International Whaling Commission (IWC) imposed a hunting ban in 1966, Blues have returned to several areas of their former range, but recovery is slow (current populations are only 1% of their former numbers).
Blue whales are so named because their skin has a light-gray-and-white mottled pattern, which appears light blue when the whale is just below the surface of the water on a sunny day. Researchers use these skin patterns, which are unique to each animal, as a means of individual whale identification. Aside from the animal’s massive size, distinguishing characteristics include its habit of showing its flukes when diving (other rorqual whales do not). Also, they have an unusually small dorsal fin which is set far back on the body.
Blue whales produce reverberating, low-frequency moans that can be heard in deep ocean waters up to 100 miles away. These moans enable the whales to remain in contact across a vast expanse of ocean.
Despite their enormous size, the Blue Whale’s diet consists almost entirely of krill, tiny shrimplike crustaceans occurring in all oceans of the world. Feeding by lunging open-mouthed into dense groups of such creatures, they can consume as much as 4.5 tons in a day. Water and food rushing into the whale’s pleated, expandable mouth is forced past hundreds of wide, black fringed baleen plates that hang from the roof of the mouth. The plates act like a sieve or comb, trapping the solid food inside the fringes and expelling the excess water. Occasionally working in pairs, Blue whales have been observed weave through schools of krill, apparently using each other’s bodies to block the escape of their prey.
Female Blue whales reach sexual maturity at approximately 5 years of age. They may give birth once every two or three years. Mating occurs during the summer season, and the gestation period lasts about 11 months. A single calf is usually born the following spring; twins are rare. The calves nurse for seven or eight months, gaining as much as 200 pounds per day in the nutrient-rich Antarctic or Arctic waters.