The largest animal on the planet, the blue whale can reach a length of more than 100 feet. Despite their size, they are remarkably skilled divers, rapidly plunging several hundred feet below the surface using their back muscles to propel them. When they emerge from the dive, they let out a torrent of water, air and mucus from their blowhole. They are found in most of the world's oceans, and are threatened by noise and other environmental pollution throughout much of their range.
Blue whales have been found in every ocean of the world. Blue whales swim individually or in small groups. Pairs are very commonly seen. Approximately 2,000 blue whales live off the California Coast and migrate to Mexico, and Costa Rica.
The blue whale eats mostly krill (small shrimp-like crustaceans) by using its baleen plates lining its mouth to sieve krill from the water. It can consume several tons of krill daily. Researchers have believed that the blue whale only eats in the summer, seldom eating during the rest of the year. But recent research has suggested that some blue whales of the north may eat year-round and that blue whales found traveling with empty stomachs may stop eating during migration and resume feeding at wintering areas.
Blue whales only mate in warmer waters and the gestation period lasts 10 to 11 months. The females give birth to only one calf in the spring which gives the calf the entire summer to grow a layer of blubber needed to protect it when traveling through colder waters. The calves nurse for around seven months. Females give birth to calves every two to three years. They remain pregnant for about one year before giving birth. When born, the blue whale calf is about 23 feet (7 m) long and weighs 5,000 to 6,000 pounds (2,700 kg). A nursing blue whale mother produces over 50 gallons (200 liters) of milk a day. At six months of age and an average length of over 52 feet (16 m), the calf is weaned. The blue whale reaches sexual maturity at around 10 years of age.
The blue whale was too swift and powerful for the 19th century whalers to hunt, but with the arrival of harpoon cannons, they became a much sought after species for their large amounts of blubber. The killing reached a peak in 1931 when 29,649 blue whales were taken. By 1966, blues were so scarce that the International Whaling Commission declared them protected throughout the world. Today, there are between 8,000-9,000 blue whales in the oceans, and they are considered an endangered species.
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