Whale

C

Reproduction

Most large species of whales migrate to the tropics to mate and give birth. Whales mate after extensive courtship rituals involving various sounds, postures, ritualized swimming, and touching and caressing. Gestation, the time between conception and birth, may range from about 10 months in river dolphins to about 16 months in sperm whales. Whales produce a single calf.

A newborn whale typically measures 30 percent or more of the mother's length and about 6 percent of her weight. A baby blue whale, for example, may be 7.6 m (25 ft) long and weigh 3 metric tons at birth. Mothers feed their newborns with milk, one of the primary reasons that scientists characterized whales as mammals. Newborn whales may nurse for up to a year before beginning to feed on their own. The largest whales can produce an estimated 600 liters (160 gallons) of milk per day. Whale milk contains 25 to 50 percent fat, compared to a fat content of 3 to 5 percent in cow milk.

Whales reach sexual maturity from 7 to 14 years of age, depending on the species. Whales may live from 20 to 60 years. Larger species live the longest.

D

Intelligence

Scientists believe that whales are intelligent animals. An anatomical feature that scientists correlate with intelligence is the degree of folding of the upper surface of the whale’s brain, the area known as the cerebral cortex. This folding increases the surface area of the brain and is found in other intelligent animals, such as elephants and dogs. Whale brains generally show as much or more folding of the cerebral cortex as is seen in humans.

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Complex behavior may reveal more about whale intelligence than brain structure. Some whales in captivity exhibit extensive learning and problem-solving skills. Dolphin curiosity and their often-eager interactions with humans also suggest a high level of intelligence. Other research indicates that dolphins have a sense of self. Studies that presented individual dolphins with mirrors and video images found that the dolphins could recognize themselves and also distinguish themselves from other dolphins.

Perhaps the most intriguing indication of whale intelligence came with the discovery in the 1970s of whale singing, most notably in humpbacks. Humpback songs, which may last more than 20 minutes, consist of a series of phrases or sequences. All of the singing whales of a particular migrating group sing very nearly the same song. The songs change progressively from year to year, resulting in entirely new songs after four or five years. Bowhead whales also sing. The Inuit people of Alaska have told researchers that they long observed that bowheads make sounds 'like a guitar playing inside the water.' Singing most commonly occurs in the winter mating grounds, suggesting that it may be part of a mating ritual. Scientists have been unable to prove that whale songs encode language in an intellectual sense. The whale songs may simply be longer versions of the mating songs also noted in birds and amphibians.

Scientists have also observed killer whales teaching their young cultural practices. Certain killer whale pods have developed the habit of attacking sea lions on beaches. Scientists have observed adults in these pods teaching the young how to attack these sea lions. The adults make mock lunges toward the beach, then roll aside to permit the juvenile “trainees” to lunge toward the beach. All studies of whale intelligence are still preliminary, however. Scientists acknowledge that they are still far from accurately measuring, or even knowing how to measure, the intelligence of whales.

IV

Types of Whales

There are more than 75 species of whale, each with its own unique characteristics. Whales range from black to white in color and from nearly 24 m (80 ft) to less than 1.2 m (4 ft) in length. They may live in salt water or fresh water, and can be found as far north as the Arctic Circle and as far south as Antarctica. With such diversity, the most common way of classifying whales is according to how they feed. The Odontoceti, or toothed whales, use teeth, and the Mysticeti, or baleen whales, use horny, fringed plates called baleen.

A

Toothed Whales

The toothed whales comprise sperm whales, beaked whales, narwhals, belugas, dolphins, and porpoises. Toothed whales commonly have teeth in the front of the lower jaw or in both jaws. Some toothed whales have teeth that are embedded in the jaw’s gums. These teeth are not exposed and do not help the whale feed on prey. Toothed whales vary in size from small harbor porpoises less than 1.5 m (less than 5 ft) long to the great sperm whales, whose adults grow up to 18 m (59 ft) long and weigh nearly 55 metric tons.

A

1

Sperm Whales

Sperm whales have a huge, barrel-shaped head with an extensive accumulation of fatty tissue, called the case, in the forehead region. Inside the case is a liquid wax called spermaceti, which was highly valued for making candles and other products during the 1800s. The sperm whale's S-shaped blowhole is near the tip of the snout instead of back on the head, as in other whales. When discharging air from the blowhole, sperm whales produce a characteristic short, wide spout of water that is directed forward and upward. The lower jaw is narrow and has from 16 to 30 teeth on each side. No exposed teeth are present in the upper jaw. Mature males may grow to about 18 m (about 59 ft) in length and weigh up to 55 metric tons, while females are smaller, growing to 12 m (39 ft).

Feeding dives by sperm whales average about 45 minutes, although some whales have been observed to stay underwater for close to two hours. Sperm whales can dive to depths of 1,000 to 2,000 m (3,300 to 6,600 ft). Water at these depths is in complete darkness, and these whales probably locate their prey using echolocation. Sperm whales specialize in feeding on large deep-sea squid. Giant squid, measuring up to 18 m (60 ft) long including tentacles, sometimes fight back, leaving deep cuts and scratches on the sperm whale’s body.

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