Socially segregated, sympatric sperm whale clans in the Atlantic Ocean

• Published in: Royal Society Open Science
• Main Authors: Gero, Shane, Bøttcher, Anne, Whitehead, Hal, Madsen, Peter Teglberg
• Other Authors: Natural Sciences and Engineering Research Council of Canada, Carlsbergfondet, Danish Council for Independent Research, Whale and Dolphin Conservation Society, Marine Alliance for Science and Technology for Scotland, Killam Trusts
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2016
• Subjects: Physeter macrocephalus; Sperm whale
• Online Access: http://dx.doi.org/10.1098/rsos.160061; https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.160061; https://royalsocietypublishing.org/doi/full-xml/10.1098/rsos.160061

Sperm whales ( Physeter macrocephalus ) are unusual in that there is good evidence for sympatric populations with distinct culturally determined behaviour, including potential acoustic markers of the population division. In the Pacific, socially segregated, vocal clans with distinct dialects coexist; by contrast, geographical variation in vocal repertoire in the Atlantic has been attributed to drift. We examine networks of acoustic repertoire similarity and social interactions for 11 social units in the Eastern Caribbean. We find the presence of two socially segregated, sympatric vocal clans whose dialects differ significantly both in terms of categorical coda types produced by each clan (Mantel test between clans: matrix correlation = 0.256; p ≤ 0.001) and when using classification-free similarity which ignores defined types (Mantel test between clans: matrix correlation = 0.180; p ≤ 0.001). The more common of the two clans makes a characteristic 1 + 1 + 3 coda, while the other less often sighted clan makes predominantly regular codas. Units were only observed associating with other units within their vocal clan. This study demonstrates that sympatric vocal clans do exist in the Atlantic, that they define a higher order level of social organization as they do in the Pacific, and suggests that cultural identity at the clan level is probably important in this species worldwide.