People generally think that the largest animals ever to live on earth were the dinosaurs, but even those giants were not as huge as the blue whale that is still alive today. Named for its blue-gray color, this huge cetacean may grow to be roughly 30.5 m (100 ft) long and weigh more that 108,000 kg (120 tons). Its close relatives include the smaller fin, humpback, sei, Bryde's, and minke whales. The blue whale and its relatives are called baleen whales because they have a feeding structure known as baleen that takes the place of teeth. Baleen is made of a flexible material containing a protein called keratin, which is also found in your fingernails and in the hooves of horses and cows.
Baleen plates hang down from the roof of the whale's mouth in rows, somewhat like the teeth of a comb. The inner edges of the baleen plates are fringed and look hairy. A large part of the whale's diet is made up of small shrimp-like animals called krill, which the animal strains with its plates of baleen. In order to get enough of these small creatures to eat, a blue whale has to filter large amounts of water. Folds of skin on its throat expand like an accordion to allow the whale to gulp in as much as 64,600 liters (17,000 gal) of water at one time.
The whale then pushes its tongue (which can be as large as a Volkswagen) to the roof of its mouth in order to force out the water. Food is caught in the hairs of the baleen and swallowed. A blue whale weighing 75 to 80 tons eats about 4 tons of krill per day during the feeding season. As summer approaches, blue whales migrate to feeding grounds near the north or south poles.
Concentrations of krill are greatest in these areas during the summer, and it is then that the whales eat huge amounts of food. Groups of blue whales can be seen at this time, especially around Antarctica. In the fall, after feeding for half a year, the whales begin to swim toward warmer water to mate and to give birth to their young in the warmer, calmer water. Females give birth to one calf every two or three years. Newborn calves are about 23 ft long and weigh almost 6000 lbs. The hungry babies may drink more than 50 gal of rich milk from their mothers daily, and grow very quickly, gaining up to 200 lbs a day.
Calves are weaned after six months and begin to strain krill from the water. This cycle of seasonal feeding and breeding migrations continues for the rest of the whale's life, which may be 90 years or more. In the early 1900's when ships became fast enough to catch them, blue whales became the major whale species hunted by people, who used the meat, oil and baleen. Baleen was used to make the stays in corsets and the ribs in umbrellas. At this time, over 200,000 blue whales were estimated to be in all of the world's oceans.
Because it was most efficient for whalers to kill one large blue whale instead of many small ones, the blue whales were over hunted and their survival was threatened. Protection came for the great whale in 1964, when fewer than 2000 animals remained, less than one per cent of the estimated population only fifty years earlier. But because not all nations presently honor this protection, it is feared that the few populations remaining are not enough to ensure the continued survival of this magnificent animal. The blue whale was listed as endangered on June 2, 1970 under the Endangered Species Conservation Act of 1969. Blue whales are severely depleted in all oceans of the world. The population status of blue whales in the Northern Hemisphere is unknown.
Sightings have increased off central California and on the Pacific coast of Mexico and Central America, but these increases may be attributed to increased observer effort rather than trends in abundance. Blue whales have been studied in the Gulf of California, Mexico and the Gulf of St. Lawrence, Canada, but trends in abundance were not apparent. An increasing trend in abundance of 5.1 percent was reported between 1979 and 1988 west of Iceland. The status of blue whales in the southern hemisphere is uncertain.
Only seven sightings of calves have been made below 60^0 S. since 1965. An analysis of 6 years of sightings in Antarctic waters collected by the International Whaling Commission suggests that blue whales may not be recovering from commercial whaling. However, the general opinion is that the Antarctic stock is certainly larger than 500 animals, with a considerably larger population for the entire southern hemisphere. A recovery plan for this species is being prepared by NMFS. A draft of the plan is scheduled to be completed in 1996. The principal cause of the decline in blue whales was commercial whaling, and prohibitions on their harvest by IWC have reduced the magnitude of the threat.
No activities in waters under the jurisdiction of the United States are known to be adversely affecting recovery of this species at the present time. Through inter agency coordination under Section 7 of the ESA, the species is protected from Federal actions that are likely to jeopardize the species.