Social structure of long-finned pilot whales (Globicephala melas) off northern Cape Breton Island, Nova Scotia

Abstract

Cetacean social structures include fluid and stable elements. Long-finned pilot whales (Globicephala melas) live in units that interact forming labile groups. In this study conducted off Cape Breton Island, between 1998–2011, we confirm unit membership predicts associations between individuals. We determine how units are structured and interact. We delineated 21 nearly-stable social units, with an average 7 members. For units where multiple individuals are sexed, both sexes are present. Most units showed long-term stability, while one showed evidence of splitting. Three units shared individuals with the largest unit (K, average size = 29). Splitting is likely triggered by size and difficulties maintaining associations between all individuals. Pilot whales face many pressures driving sociality at a range of temporal and social scales producing a multilevel society. While we have produced a more detailed model of long-finned pilot whale social structure, there are still unanswered questions, particularly whether units are strict matrilines.