Social organization in northern bottlenose whales (Hyperoodon ampullatus ): not driven by deep water foraging?

Shannon Gowans, Hal Whitehead and Sascha K. Hooker. 2001.

Animal Behaviour 62: 369-377.

It is postulated that deep water foraging in sperm whales (Physeter macrocephalus) has led to communal care of young and long-term females bonds. By studying the social organization of a second, unrelated, deep-diving species, the northern bottlenose whale, we investigated the role that deep-diving may play in the evolution of cetacean sociality. Northern bottlenose whales in a deep water canyon, the Gully off Nova Scotia, form small groups (mean +/- SD = 3.04 +/- 1.86). Associations within age/sex classes (female/immature, sub-adult male and mature male) were significantly higher than associations between different classes. Females and immature bottlenose whales formed a loose network of associations, showing no preferential associations with particular individuals or those from specific age/sex classes nor any long term bonds. Mature and sub-adult males had stronger associations with individuals in their own class, and associations between some males lasted for several years, although males also formed many short term associations. Overall the social organization of northern bottlenose whales in the Gully appears to resemble that of some bottlenose dolphins (Tursiops truncatus) living in shallow, enclosed bays. Thus deep water foraging does not appear to necessarily lead to the evolution of long-term bonds between females.

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