Sperm whale - Physeter macrocephalus

Cachalot

The name sperm whale comes from the enormous bulbous spermaceti organ in the head. The alternative name "cachalot" was the name given by the early whalers as when they caught one they'd just "caught a lot"!

Only males are found in Antarctic waters. There is a large degree of sexual dimorphism (difference in appearance between males and females) with males being about one and a half times longer, but considerably heavier than the females.

Sperm whales are Odontocetes - toothed whales rather than filter feeders and are the deepest and longest of all whale divers catching giant squid in the dark ocean depths. Most dives are thought to be about 400-600m in depth, but they may be able to dive as deep as 3000m.

The "blow" of the sperm whale is the most characteristic of any whale. It is directed forwards and to the left, it projects about 5m. On calm days or when there is very little wind, the direction of the blow can be easily used to identify sperm whales even at some considerable distance.

Sperm whales are easily the largest toothed carnivores on earth. The baleen whales are also carnivores as they eat other animals, but they do so by capturing hundreds or thousands at a time by filter feeding and so are not usually classed with whales that have have teeth and hunt individual prey.

Unusually, sperm whales only have teeth in their lower jaw, these fitting into depressions in the upper jaw. There are from 17 to 29 pairs of teeth and the depressions in the upper jaw show tiny undeveloped teeth. The teeth are large, up to 10" (25cm) long in old males, they are conical and very strong being designed for grasping and disabling slippery prey such as squid rather than being sharp cutting teeth as in many other animals.  

Orcas will sometimes hunt other whales even the giant blue whale, but they never approach the sperm whale with it's formidable lower jaw.

The area around a sperm whales mouth, lips and lower jaw is coloured white against the dark grey - brown of the rest of the animal. This coloration is thought to assist the whales when they are in the dark ocean depths hunting for squid with the possibility that there may even be phosphorescent bacteria that live on the white skin so making light - most squid are readily attracted to light in the darkness.

Of greatest fascination in the sperm whale is the huge spermaceti organ in the head that causes the head to be from 1/3rd to a 1/4 of the length of the animal. Clearly this is an enormous structure and while it has similar counterparts in other Odontocetes - many dolphins and small toothed whales have a bulbous "melon" with a similar internal structure - it is developed to an extreme in the sperm whale. The organ itself is full of oil which becomes a solid waxy substance at room temperature. About 25 to 40 barrels of whale oil could be had from a sperm whale of average size. Extremes of over 100 barrels are found in legend.

The reason for this organ is unknown as is so much whale biology, due to the whales being so difficult to study. There are several theories as to what this organ is for and it may well have more than one of these functions:

Unlike baleen whales, which form only temporary bonds, sperm whales live in extended family units of up to 50 individuals, that for the females are lifelong associations. The males in high latitudes towards the poles however tend to be solitary. These schools of sperm whales that form are of several type segregated by age and status, for instance, matriarchal nursery schools (females and calves), juvenile schools, bachelor schools and bull schools have been seen.

The nursery schools in particular are very stable and individual whales may remain in the same school for several years. Sperm whales have been seen to exhibit altruism to other members of the school in similar ways to those seen in dolphins and other smaller Odontocetes. Baby-sitting and assisting injured school members are behaviours seen by other mothers and young males in such schools.

Sperm whales are found in all oceans and latitudes from the equator to the edge of the polar pack ice (males only in the polar regions). They frequent deep waters which means that they are usually found offshore unless depths of more than 200m are found near to shores for example off volcanic and oceanic islands. Most commonly they are found in submarine canyons at the edges of the continental shelf, but may also occur in mid-ocean. They are found in deep waters as this is where their prey of squid are found.

A whole range of cephalopods (squid, octopuses and cuttlefish), deep-sea fish, and non-food items have been found in the stomachs of sperm whales around the world. Cephalopods however are thought to be the major prey. In some parts of the world, sperm whales have been known to steal the catch from longlines set by fishing boats. The skin of most sperm whales bears the scars from the suckers of the squid that they feed on.

Copyright 2001 Paul Ward  |  copyright issues  |  privacy policy  |     |  Last modified:  May 05, 2008