Maternal behaviour of humpback whales in southeast Alaska




Szabo, Andrew Ronald.

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In this study, I characterize the maternal care patterns of humpback whales in southeast Alaska. Through a study of proximity behaviour, I show that humpbacks behave similarly to terrestrial ungulate 'followers': the cow and calf are rarely more than several body lengths apart; proximity between the cow and calf is greatest during periods of travel relative to other behaviours; and, proximity is greatest when the dive behaviour of the pair is synchronized. Unlike that observed in typical follower species, however, proximity is not found to decrease significantly as the pair's association lengthens. To account for this, I argue that the length of the observation period was insufficient to detect such a trend since maternal pairs remain together for several months after the last observations. In addition, I analyze the diving behaviour of the maternal pair to examine the potential negative consequences for the female associated with the follower tactic in humpbacks. The results suggest that several behavioural modifications are made by the cow and calf in an effort to minimize the duration of separation between the two. Ultimately, I argue that behaviour observed in humpback whales is commensurate in function with following behaviour in terrestrial ungulate followers. Humpbacks are migratory, and as in many migratory species, following behaviour provides a mechanism whereby the maternal dyad can maintain close proximity during periods of travel. Moreover, as with many follower species, humpbacks can rely upon their large size as a means of defence against offspring predation. Finally, although obvious differences exist between the habitats in which humpbacks and ungulate followers reside, arguably both are open habitats that lack the cover necessary to allow for offspring concealment.