Sperm whale

Distribution

Sperm whales are found in all oceans of the world, but they are concentrated in areas of highly productive and deep water.

Males and females have quite different distributions. Females tend to remain below 40° latitude, whereas large males can be found right up to the southern limits of the ice in the North Atlantic. Only males are found as far north as Svalbard. In mid-latitudes there is a north-south seasonal migration, with them moving pole-ward in summer. Females appear to occupy home ranges whereas males show more variable movement patterns; some remain in coastal waters over periods of years, while others roam much more widely.

General ecology

There is thought to be approximately 6,200 sperm whales in the Northeast Atlantic region.

Females are highly social and live together with other females and their young in groups that usually number about 12 individuals. Groups containing young calves stagger their diving activities such that some adult animals are always on the surface with the calves. Groups can join together with others for some days at a time, and females have been documented to shift groups. Members of a group are very cohesive and perform group defence against predators, forming tight clusters with calves on the inside of the group. Sperm whales are sometimes very active at the surface, breaching, lobtailing and rolling, while at other times they simply rest close together.

Young males leave their mother’s pod and form bachelor schools with similarly sized males. As males grow older the groups they occur in shrink in size, until very large males become solitary.

Sperm whales perform quiet squeals and trumpets, but for the most part the sounds they produce are high frequency clicks. The most common click trains are thought to be echolocation; used as a means of finding food. However, some stereotyped click trains likely have a social function.

Sperm whales are very deep divers, and are largely benthic feeders. Routine dives are to 400 m for periods of 35 minutes, but they can dive to vast depths for periods of over one hour. The maximum recorded depth is 3,000 m.

Sperm whales predominantly eat squid but also eat large fish that inhabit deep waters. Killer whales are their principle predator, although it is thought that large sharks may pose a threat to young animals.

Life history and reproduction

Sperm whales have a gestation period of 14–16 months and calves are suckled for several years, although they start eating solid food before they are 12 months old. The specific time of mating and birthing is not known.

Large, mature males migrate south for breeding purposes, and are intermittently observed associating with female groups. Females reach sexual maturity when they are about nine years old. They give birth about every five years thereafter. Males reach sexual maturity at about 10 years old, but are unlikely able to participate in mating before they are 20 or more.

Longevity is not known, but sperm whales are thought to live to be over 70 years of age.

Management status and monitoring

Hunting of sperm whales commenced in the early 1800s and by the middle of that century thousand of animals were taken annually. This species was highly valued because of the superb quality of the oil from the spermaceti organ. It is thought that whaling, particularly that which occurred following World War II, significantly reduced sperm whale numbers, particularly males because these large animals were preferred. There is no current hunting of sperm whales in the North Atlantic region.

Sperm whales are protected in Svalbard.