Mating Behaviour of Whales

Whales have rarely been observed in the act of mating – partly because the act appears to be of very brief duration – though one instance of humpback whale copulation has been captured on camera. Behaviour prior to copulation has, however, been observed. This varies from species to species. Some baleen whales, such as blues and humpbacks, ‘sing’ to attract mates, and humpback males actually engage in mating competition using song. Such competition can often turn violent: male humpbacks can usually be told apart from females by the heavy scarring they acquire in mating contests.

Some species, such as sperm whales, engage in harem formation during the mating season a single, dominant male acquires exclusive mating rights to a group of females, which he then defends against competing males. Unsuccessful competitors, who tend to be smaller in size, form ‘bachelor’ groups. Battles sometimes take place between rival males for control of a harem.

Dolphin males are known to form ‘gangs’ in which individual males cooperate to separate an ovulating female from a school, sequestering and bullying her until, exhausted, she is forced into mating with one or all of them. This behaviour can occasionally be observed when spinner dolphins move inshore to rest and socialize.

Among Risso’s dolphins, males fight amongst themselves over females – hence the tooth marks and scarring that decorate their bodies.

Dolphin gangs also serve to protect the schools of which they are members from rival schools and other threats.

Orcas, which live in relatively small, closely related pods, avoid inbreeding by mating exclusively with individuals from other pods.

Text by Howard Martenstyn, Out of the Blue

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