The Sperm Whale Families

A Sperm Whale's Life:

The sperm whale is truly an animal of extremes. The sperm whale is the largest toothed whale. Among cetaceans, the sperm whale displays the largest difference in body size between the sexes as males can reach up to 18 meters or 60 feet and weigh up to 60 metric tonnes or 125 000 lbs, while the females are about a third shorter and half as heavy. The sperm whale also has the largest brain and the longest intestine on the planet.

A sperm whale's life is similar to humans and other long lived mammals. Sperm whale mothers are pregnant for about 15-18 months. Calves are born at about 4m or 13ft and the average weight at birth is around 1 metric tonne or about 2200 lbs. Sperm whales nurse for at least 3 years during which time they do not appear to dive deeply with thier mothers. As a result, other members of the calf's family remain at the surface to babysit while its mother is at depth feeding. Calves appear to begin fluking (lifting their tail out fo the water to make a deep dive) at around 3 years of age. Sexual maturity for both sexes is in their early teens, although males slightly later than females. Calving rate is around one every four years. Adult females are thought to go through menopause in their fourties and most individuals can reach as old as 70.



How Sperm Whale Families are Organized:

Female and immature sperm whales live in stable groups, called "Units". Units are mostly made up of matrilines - meaning a female line from grandmothers to mothers to daughters. Females born in a unit will live with the other females in the unit for life, while males will leave their family unit at maturity and live alone for most of their lives searching for mates. Family units of females range in size from the smaller units of the Caribbean (about 7 animals) to larger units in the Pacific (can be over 14 animals). Within a family, all females care for each other’s calves. Mothers make deep dives for food (2 km deep or 1.2 miles down) and must leave their babies at the surface because they can’t dive that deep. While mothers are down, other females babysit their calves to protect them from predators. In Dominica, it seems as though every calf has a particular babysitter who tends to be mom’s closest relative and so typically they are the calves’ aunt or great-aunt.

In the Pacific, family units often gather into “Groups” where two or more families can spend a few days with other. In Dominica, however, most of the time we observe single family units alone.

Finally, tens of thousands of sperm whales make up one of several "Vocal Clans" each with a distinct vocal dialect. Members of different vocal clans also appear to differ in their movement patterns, habitat-use, feeding success, diet, and reproductive success. These truly are different whale cultures.



Sperm Whale Units around Dominica:

Since 2005, we have spent hundreds of hours with over 20 differnt sperm whale families. Click on one of the units below to meet some of the individuals in the most well-known families.

Unit F - "The Group of Seven"
Unit J - "Jocasta's Unit"
Unit A - "The Atwood Collective"
Unit U - "The Utensils"<