BALAENOPTERIDAE (Fin-backed Whale Family)
The humpback whale is fairly easy to recognize: it has a robust body, large flippers, and irregular rows of conspicuous fleshy knobseach with one or two bristly hairson the snout and along the lower jaw. Its body shape differs from other balaenopterids, such as the finback whale: the head is broader and its stocky body tapers abruptly to the tail. The flippers are also distinctive narrow and nearly 1/3 the total length of the bodywith irregular scalloping along the front margins.
The humpback whale is black on top, with variable amounts of white below. The undersides of the flippers and flukes are almost all white. The baleen plates are about three feet long, black with black or olive-black bristles; there are 300-320 plates on each side of the upper jaw. The low triangular dorsal fin is small and sits well back on the body, about 2/3 of the way back from the head. The flukes are deeply notched and irregularly shaped on the rear margins. It has a pair of blowholes on top of its head, and a distinctive, rounded projection on the tip of its lower jaw. There are approximately 20 lengthwise grooves on the throat and chest. Its spout is an expanding column, somewhat balloon-shaped, and accompanied by a puff of vapor. The spout can rise as high as 6 meters (20 feet).
Size: It ranges in size from 13 to 16 meters (40-52 feet), and weighs about 30-40 metric tons. The females are slightly larger than the males.
Range and Habitat
There are presently three major populations of humpback whales in the world: one in the North Atlantic; another in the Southern Hemisphere, ranging seasonally from the Antarctic Seas to the South Pacific Ocean; and the third in the North Pacific (Orr and Helm). These populations migrate between the polar oceanic waters in summer, and tropical or subtropical breeding grounds in the winter.
The North Pacific population summers in the Bering Sea and winters in the warm waters around Hawaii or off the west coast of Mexico. This species is frequently seen along the California coast during the migration, principally between April and November.
The humpback whale lives along the coast of all major oceans, usually on the continental shelf or island banks. It is sometimes found on the open sea. Although not part of its usual habitat, a humpback whale will occasionally lose direction and swim very close inshore, even into harbors and up rivers.
Behavior: The humpback is considered the most acrobatic of the whales. It may leap from the water, belly up, arching backwards, and plunging headfirst into the water. This habit of breaching is one of the whale's most distinctive traits. It also "lobtails"beats the surface with its flukes or strikes the water with its flippers, making a loud slapping sound. When going into a deep dive, it arches back strongly and exposes its flukes above the water's surface.
The humpback is also known for its song. This species is very vocal, and can create a wide variety of sounds, which are strung together to form a long series of repeated phrases. Each phrase may last from five to 35 minutes and may be repeated without interruption for several hours. The songs appear to be specific to separate populations of whales, and change slightly from year to year. The songs can often be heard above the water surface.
Reproduction: Courtship, mating, and birthing all take place in the warm waters of their winter breeding grounds. Sexual maturity is reached by 10 years. The gestation period is 10-11 months, and mating can occur shortly after the young are born. Newborn calves measure about 4.5 meters (15 feet), and weight over a metric ton. A calf may stay with its mother for as long as a year, but can be weaned as early as 6 months.
Diet: These whales feed on krill (shrimplike crustacean), schools of small fish such as herring, and plankton. Like other baleen whales, the humpback obtains its food by straining it from water gulped into its mouth. It usually captures prey by "lunge feeding,"swimming rapidly from below or near the surface and lunging, mouth open, into schools of small fish. Groups of humpbacks will also concentrate their preyusually a school of fishby forming a net of bubbles. Three or four humpbacks will dive about 15 meters (50 feet) below their prey and slowly swim in a circle, releasing air bubbles as they go. The fish are trapped between the "net" of bubbles and the water's surface. The whales then consume them by gulping them in with water.
The humpback has a relatively low oil yield, but was still considered commercially valuable because of its large size, and it was heavily hunted during the early to mid-twentieth century. Prior to human exploitation, the humpback whale populations were believed to have totaled approximately 100,000 individuals worldwide. The current world population is approximately 6,000, with about 1,000 living in the North Pacific. The humpback whale has been protected since the mid-1960s, and is still considered an endangered species.
Top: Humpback Whale off Cabo San Lucas; middle two: group of competitive males. All photographed by Pete and Gretchen Pederson
One of the most interesting traits of humpback whales are their songs. The songs are produced primarily if not exclusively by the males, and are thought to be the longest continuous vocalizations of any mammal.