Dive Dry with Dr. Bill

081: Sperm Whale

I can just see Gregory Peck... er, I mean Captain Ahab holding his harpoon ready to strike the white leviathan. Although this largest of all the toothed whales is usually dark brown, dark gray or even black in color, albino sperm whales do occur... and not just in Herman Melville's book. Moby Dick's less alabaster relatives are known from all the oceans of the world. However they are primarily oceanic and are not usually seen close to shore unless the water is very deep like in the Sea of Cortez or off volcanic islands.

The triangular tail fluke is broad and powerful but the flippers are short. The dorsal fin is reduced to a series of humps on the back. The head of this species is huge, comprising about one third of the body length (up to 67 feet in males and 43 feet in females). The smaller females weigh about 20 tons while the males may be nearly 60 tons. The lower jaw contains about 50 teeth in two parallel rows and the upper jaw has very small, non-functional teeth. Each tooth may weigh over two pounds.

At sea very little of this whale is usually visible above the surface. they may appear like a large log floating at the surface. However, their blow from the single blowhole on the left side is fairly distinctive. It extends about 16 feet forward and to the left of the animal. Normally swimming speeds rarely exceed six mph but when threatened they can reach nearly 20 mph.

Sperm whales in some areas are rather picky eaters, taking only squid and octopi. They prefer areas conducive to squid production- deep water with cold water upwellings. In other areas they may add sharks, rays, cod and other fish to the menu. They may dive to depths in excess of 10,000 feet and stay below the surface for 90 minutes. With my big tank I can easily match their duration, but rarely go deeper than 130 feet. I'd need more blubber (er, insulation) than I have to do that.

The social unit of this species includes about 10-20 mature females (cows) with their calves, and these units are tight often lasting from birth until death. At times they congregate into groups of hundreds or thousands and travel as a unit. Young males apparently are not inclined to participate in family life and form small pods of unattached "bachelors." The older males (bulls) are even less inclined and venture into higher latitudes (both north and south) into cold temperate and polar waters where they live in solitude.

During breeding season, several males will join the cow-calf groups. Males may fight for dominance within the group. Only 10-25% of the adult males are able to form breeding groups and each successful male will take about 10 females into his harem. Mating generally occurs in the spring and calving in the fall. Cows are sexually mature at 7-11 years while the males are rarely accepted into breeding groups until they are 25-27 years (ouch!) even though they may mature sexually much earlier. Females only give birth once every 5-7 years with the gestation period estimated at 14-19 months. The calves weigh about one ton and are around 12 feet at birth. The young nurse for a little over two years but in some cases up to 13 years!

Communication is through a series of clicks, some of which scientists believe are powerful enough to stun their prey. These sounds are also used for navigation through echolocation. They produce a variety of other sounds referred to by Ellis as groans, whistles, chirps, pings, squeaks and wheezes. Individuals have their own unique repetitive sequence of clicks that are heard only when greeting another sperm whale. The sperm whale has the largest brain of any mammal, weighing up to 20 pounds. The function of the structure containing the spermaceti is not known. Scientists speculate that it might help force air out of the lungs prior to diving, absorb nitrogen in deep water (to prevent the bends), regulate buoyancy during diving or be involved in sound production or reception.

Sperm whales were hunted for the oil rendered from their blubber, the wax (spermaceti) found in their large heads, and ambergris which was used to make perfume. The dark, oily meat was not used by the majority of whaling nations. In its early history, whaling for this species was dominated by Americans. The peak recorded harvest of 29,300 was in 1963-64. The International Whaling Commission first restricted their take in 1971 and by 1984 banned all commercial take. They may live more than 70 years. Some sources estimated the population of sperm whales world-wide at two million., yet new information suggests the population may be much lower.

© 2004 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Sperm whales have a distinctive blow streaming forward and slightly to the left;
whales raising their tail flukes before diving to depth

This document maintained by Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia