Humpback Whale

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Introduction

Humpback Whale, large whale known for its acrobatic leaps from the water and complex songs. Humpback whales belong to the rorqual group of baleen whales and occur in all oceans. Once heavily hunted, humpbacks have made a small recovery in some regions of the world. Humpbacks are one of the best known and most recognizable of all whales.

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Habitat and Range

Humpback whales are found mainly in waters along coasts and continental shelves in summer, migrating to feeding grounds as far as the pack ice near the poles. In winter they migrate to shallow, tropical breeding areas, often around islands or reefs. Some populations make the longest migrations recorded for any mammal—more than 8,200 km (5,100 mi) from Central America to Antarctica. The northern and southern hemisphere forms are distinctly different.

Humpback whales may sometimes become disoriented during migrations and swim up rivers. Humpbacks that enter San Francisco Bay in California have strayed into the Sacramento River on a number of occasions. In a widely-covered incident in 1985, a humpback whale nicknamed Humphrey swam almost a month in the Sacramento River but was eventually lured back out to sea.

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Description

Humpbacks grow to between 12 m (40 ft) and 15 m (50 ft) long. The largest reported length is 17 m (57 ft). They may weigh between 30 and 48 tons. Adult female humpbacks are somewhat larger than adult males. The average life span is about 45 to 50 years.

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Humpback whales have a dorsal fin about two-thirds of the way from the front of the body. A characteristic high humping or arching of the back when diving is the source of the common name “humpback.” They have long, thin, winglike pectoral fins that are the source of their scientific name Megaptera, formed from Greek words meaning “big wing.” Their fins measure about one-third their body length or about 4.5 m (15 ft). Humpbacks also have a massive tail, the underside of which is mottled white and black and can vary distinctly in shading pattern. Because humpback whales usually throw their tails above water just before a deep dive, researchers have used the distinctive tail coloration and the shape of the trailing edge of the tail to identify several thousand individuals. Another characteristic feature of humpbacks are rows of large fleshy knobs on their jaws and snouts.

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Diet and Feeding

Humpback whales feed on krill, tiny shrimplike crustaceans, and small fish, including herring and mackerel. They feed during the spring, summer, and fall, but usually do not eat during the winter months spent in warm, tropical waters. During a feeding lunge through clouds or schools of prey, the whale's throat expands tremendously. This expansion is aided by throat pleats, or folds, which open up, accordionlike, to as far back as the navel. The whale closes its mouth around tons of water and prey and then uses its giant tongue to push the water out through about 300 baleen plates that hang from the upper jaw and act as a sieve.

Humpbacks may feed in social groups of up to 22 whales, all lunging at the same time. Individuals or small groups may sometimes corral prey with their tails and long flippers or by blowing bubbles around schools of prey to form bubble walls, a technique dubbed a bubblenet.

In 2007 scientists announced that they had recorded humpback whales making clicking and buzzing sounds while feeding at night. Like other baleen whales, humpbacks were known to use relatively low-pitched sounds to communicate with other members of their species. However, the use of special underwater sounds to help find prey was previously thought to occur only in toothed whales, which use high-pitched sounds to echolocate.

The main natural predators on humpback whales are killer whales, which usually attack humpback calves. How often or how successfully killer whales attack adult humpbacks is not known, although adult humpbacks sometimes have bite scars.

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