Blue Whale

I

Introduction

Blue Whale, largest whale, and the largest living creature on Earth, exceeding 30 m (100 ft) in length. Blue whales belong to a fast-swimming group of baleen whales called rorquals and are found in all oceans of the world. They mainly feed on tiny shrimplike invertebrates called krill. Blue whales were hunted nearly to extinction by the 1960s and remain endangered, with only a small recovery in numbers since official protection began in 1966. The blue whale is also known as the sulfur-bottom whale and the great northern rorqual.

II

Habitat and Range

Blue whales are mainly found in deep water along the edges of continental shelves and along ice packs. Scientists generally recognize three subspecies of blue whales found in three geographic regions: a subspecies that lives in the Northern Hemisphere, a subspecies that lives mainly in Antarctic waters, and a subspecies sometimes called the “pygmy blue whale” that lives in a zone in the southern Indian Ocean and western South Pacific. Most populations of blue whales migrate extensively, traveling from the tropics or near tropics in winter to the edges of the pack ice in the northern and southern hemispheres in summer.

III

Physical Description

Blue whales may reach over 24 m (80 ft) in length; mature females are usually slightly longer than mature males. Blue whales in the Antarctic region of the Southern Hemisphere grow somewhat larger than those in the Northern Hemisphere. The longest blue whale recorded by whalers measured 33.6 m (110 ft).

As adults, blue whales can weigh more than 100 tons. Females are larger than males of the same age, the largest sometimes weighing as much as 150 tons. The heaviest blue whale caught by whalers weighed 190 tons. Blue whales are likely the most massive creatures to ever live on Earth, exceeding the largest dinosaurs that lived on land. Some giant plant-eating dinosaurs known as sauropods may have grown up to 39 m (130 ft) long and may have weighed up to 100 tons.

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The internal organs of blue whales are also enormous. The tongue can weigh more than two tons. The heart is the size of a small car and beats about eight times a minute, compared to about 70 times a minute in humans.

The blue whale has a small dorsal fin set far back on the body. The powerful flukes (tail fins) can measure 7.6 m (25 ft) across. The flippers are about 2.4 m (8 ft) long. The whale’s blowhole has a large raised “splash guard” in front. The 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. The mottled pattern, which is unique to each animal, has been used by researchers to identify individual whales. Microscopic algae called diatoms sometimes coat the underbelly, resulting in a yellowish appearance that led to the old name “sulfur-bottom whale.”

Studies of yearly growth rings in waxy inner ear plugs found in blue whales indicate some individuals may live more than 100 years. Average life spans are estimated to be between 40 and 90 years.

IV

Behavior

A

Swimming and Diving

Blue whales can swim at up to 35 km/h (22 mph) and can dive for periods as long as 35 minutes. When feeding, however, they swim much more slowly and generally dive for periods lasting less than 20 minutes. Like all marine mammals, they must come to the surface to breathe. They produce a spout of moist, exhaled air that can reach 10 to 12 m (34 to 40 ft) high, the highest spout of any whale.

Blue whales usually swim alone or in pairs. They are sometimes found in small pods (groups) and may occur in pods as large as 50 when feeding on swarms of krill or other prey.

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