Three members of Unit R courtesy of Amanda Cotton
Sperm whales are animals that form lifelong relationships, that babysit for each other, that have family traditions passed on by grandmothers, that learn a communal dialect, and have different ways of life that resemble our various cultures, some of which coexist in in multicultural societies. They live rich, complex and interesting lives that many of us would be surprise to learn about.
The sperm whales off Dominica are predominantly groups of females and their dependent calves living together in 'units'. In the Caribbean, these units are small, about 7 animals, and appear to be matrilineal, meaning its a female line of grandmothers, mothers, and their calves; so we often refer to them as families. Young males leave their families in their early teens to roam the open ocean, mostly alone, and may never see their families again. Units of females and their young regularly travel across ranges spanning several islands in the Antilles, but they appear to remain in the Caribbean as these families have never be identified in the neighbouring waters in the Gulf of Mexico or the Sargasso Sea, where there is also active research on sperm whales.
We have identified over 20 different whale families which use the waters off Dominica, but there are about 10 that we see very regularly. We know they have been using these waters since at least 1984 based on our pictures, but likely much longer based on their life history. Sperm whales can live to be older then 70 years. Living that long means that you meet a lot of other whales over your lifetime and it turns out that families have preferences with each other. These social preferences endure across decades suggesting that individuals can remember each other across long separations.
We think this social recognition is mediated by distinct dialects of Morse code-like social calls termed ‘codas’. Each family has a slightly different coda repertoire, but also share coda types with the other units in the Caribbean. Shared repertoires delineate socially segregated ‘vocal clans’ – collections of units that share a similar coda dialect. Units which share the same dialect associate and spend time together and units that have different repertoires never gather together. In the Caribbean, the '1+1+3' coda type, which sounds like 'Click-pause-Click-pause-Click-Click-Click', is unique to the region, it has been produced in the same way for at least the last thirty years, and is made the same way by all the whales which use it. Its like a marker of Caribbean nationality.
Learn more about the sperm whales families in our Flukebook
Find out what we have learned from thousands of hours in their company read our Publications
Listen to Shane talk about sperm whale codas: