A sperm whale is seen swimming on the Indian Ocean surface.
Credit: Reuters Photo
Sperm whales, found in most of the world’s oceans, are incredible giants with the most enormous noses and the biggest brains in the animal world. They hunt deep in the waters using echolocation clicks like bats do. Their underwater clicks have the highest sound pressure. Sperm whales take their name after spermaceti, a unique organ inside their curved heads, which acts like a sonar to produce echolocation clicks and contains a waxy liquid called sperm oil.
Before humans discovered fossil fuels, sperm oil ran the world: it lit lamps and oiled machines and acted as a protective coating to prevent rust. The demand for sperm oil was so high that between 1712 and 1982, whalers killed more than a million sperm whales, pushing the species to the verge of extinction and inspiring tales like Moby Dick.
Like many other whales, sperm whales live in matriarchal groups (called pods) of ten or more females, who form lifelong bonds, suckle each other’s infants, and babysit calves. Males leave their natal groups in their teens and head to cooler oceans, while females and their calves roam the warm waters of the tropics. This geographical separation between males and females is the widest sexual segregation of all species.
In recent years, studies on whale societies have revealed exciting insights into whale cultures and communication, which differ even among the same species. Sperm whales speak to each other using a sequence of brief ultrasonic clicks called codas. Subtle differences in the pattern of codas—much like dialects in a human language—divide sperm whales into clans of about 20,000 whales. Each clan has its code and culture.
Although two or more clans share the same parts of the ocean, the whales socialise only with the members of their clans. Sperm whale societies are also very democratic: using codas, the group members make collective decisions on where to go, where to hunt, when to feed and how fast to go. Scientists believe understanding the complex dynamics of these clans can inform what drives human societies and their evolution.