Blue Whale Facts
Imagine an animal so big you could not see from one end to the other if you stood ten feet from it and you have the blue whale. Here are the large blue whale facts.
Blue Whale Facts
The blue whale (Balaenoptera musculus) is the largest living animal. It is a member of the group of whales known as rorquals. Rorquals are differentiated from other baleen whales by having dorsal fins and long grooves along the throat. The grooves act like pleats, allowing the throat area to balloon out with water when the whale is feeding. Blue whales have from 55 to 88 of these grooves, some extending from the chin to the navel. Other species in the rorqual group include the fin whale and humpback whale.
Blue whales from the southern hemisphere can reach 100 feet in length. Northern hemisphere animals are usually smaller, reaching 75-80 feet and weighing 200,000 pounds. Fully grown females are usually larger than males. Blue whales are blue-gray in color with lighter mottling on the sides and back. The darkness of the color and the amount of mottling can vary between animals. The undersides of the fins are white. Growth of diatoms on the belly area of blue whales may give a yellowish color that has caused them to be called sulphur-bottom whales. The head of a blue whale, when viewed from above, is wide and flat, somewhat like a gothic arch. When breathing, a blue whale can spout water up to 25 to 30 feet in the air. Spouts may last for up to 5 seconds. The dorsal fin on a blue whale is small, about one foot high.
Blue whales are found in all of the world's oceans from the arctic to the Antarctic. In the north Pacific, however, they rarely enter the Bering Sea. Blue whales may migrate long distances between equatorial wintering grounds and high latitude feeding areas. In the eastern north Pacific, they winter off southern and Baja California. During spring and summer, blue whales may be found from central California northward through the Gulf of Alaska. Blue whales are found most frequently along the edges of continental shelves.
Prior to whaling, the worldwide population of blue whales is believed to have been about 200,000 animals. Only 8,000 to 12,000 are estimated to be alive today. Blue whales have always been more abundant in the Antarctic than in the northern hemisphere. An estimated 4,900 to 6,000 blue whales are believed to have inhabited the north Pacific prior to whaling. The north Pacific population is now estimated at 1,200 to 1,700 animals.
Of all the great whales, the blue whale has the most limited diet. It feeds almost exclusively on shrimp-like krill. It has been estimated that an average blue whale needs to eat 40 million krill per day to meet its energy requirements. In the north Pacific, the krill species Euphausia pacifica and Thysanoessa spinifera are the main foods of blue whales. These two species occur in dense aggregations near the ocean's surface. A blue whale feeds by gulping huge quantities of water into its large mouth and expandable throat area. The animal then tightens its throat muscles, forcing the water across its baleen plates and out of the mouth. The krill are caught in the filter created by the overlapping fibrous edges of the baleen plates. The krill are wiped off the baleen by the tongue and swallowed.
The age at which female blue whales become mature is still not determined, but it has been estimated at either 5 or 10 years of age. Upon reaching sexual maturity, females bear a single calf every two to three years. In the northern hemisphere, blue whales calve and mate in late fall and winter. The gestation period is 10 to 11 months. Calves are about 23 feet long when born and weigh over 5,000 pounds. The calves nurse for about seven months and grow more than 200 pounds per day. When weaned, calves weigh about 50,000 pounds and are approximately 50 feet long.
Humans have been the main source of non-natural mortality for blue whales. Because of their speed and size, blue whales were not hunted in the early days of whaling. In the late 1800s, however, the advent of steam powered vessels and more powerful harpoon guns led to the taking of hundreds of thousands of these animals. Of the approximately 360,000 blue whales killed by whalers between 1910 and 1966, about 330,000 were killed in the Antarctic. About 8,200 were taken in the north Pacific during the same period. Hunting of blue whales was banned by the International Whaling Commission in 1966, and there have been no intentional killings of blue whales in recent years. Killer whales also kill blue whales, but the extent of this source of mortality is not known.
Despite being the largest animal on our planet, our Blue Whale facts are not all they could be. After hunting them to near extinction, this should hardly be a surprise.
