Blue whales are the largest animal to have ever lived on earth. Their tongues weigh as much as an elephant, their hearts as much as a car and a human could swim through their blood vessels. Growing up to 30 metres in length and weighing up to 200 tonnes in total, these giant mammals inhabit the open ocean and live to be around 80-90 years old in the wild.
The blue whale has a wide distribution, occurring in all oceans except the Arctic. It is absent from some regional seas such as the Mediterranean, Okhotsk and Bering seas.
Unlike dolphins and orcas, blue whales are baleen whales, meaning they have fringed plates of keratin (baleen) attached to their upper jaws. They feed by first swallowing an enormous mouthful of water, expanding the pleated skin on their throat and belly to take it in. Water is then pushed out through the baleen plates using the tongue, leaving behind food items to be digested. Blue whales feed almost entirely on Krill, a tiny animal that resembles a shrimp. At certain times of the year, a single adult blue whale can consume around 4 tons of krill a day.
Blue whales are viviparous, meaning they give birth to live young that have developed inside the body. Reproduction is a slow process, with a single calf being born every 2-3 years. In the first year of a calves life approximately 90 kilograms of weight is gained per day through the daily intake of up to 50 gallons of milk.
Blue whales normally roam the ocean as individuals or in pairs. They are thought to spend the summer feeding in polar waters before undergoing a lengthy migration to waters nearer the equator in winter. These giants swim at around 5 miles per hour but can reach speeds of 20 miles per hour when they need to. Vocalisations including groaning are produced in order to communicate with others and navigate the ocean depths. It is believed that these vocalisations are so loud they can be heard up to 1000 miles away by other blue whales.
Threats and Conservation
Blue whales are currently classed as endangered by the IUCN Red List. Between 10,000 and 25,000 are thought to remain in the world’s oceans. In the 1900s, blue whales suffered heavy losses through whaling. It is though that between 1900 and the mid-1960s, some 360,000 blue whales were slaughtered. They finally came under protection in 1966 by the International Whaling Commission, but the motion does not apply to Iceland, Norway the Russian federation. Blue whales have few predators but are known to suffer attacks by sharks and killer whales, and many are injured or die each year from impacts with large ships.
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