Social segregation of humpback whales in contrasted coastal and oceanic breeding habitats

• Published in: Journal of Mammalogy
• Main Authors: Derville, Solène, Torres, Leigh, G, Garrigue, Claire
• Other Authors: Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE Nouvelle-Calédonie ), Institut de Recherche pour le Développement (IRD Nouvelle-Calédonie )-Délégation Ifremer de Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de la Nouvelle-Calédonie (UNC)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université (SU), Opération Cétacés, UPMC - Institut de Formation Doctorale (IFD ), Université Pierre et Marie Curie - Paris 6 (UPMC), Marine Mammal Institute, Oregon State University (OSU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDV.BA.ZV]Life Sciences [q-bio]/Animal biology/Vertebrate Zoology; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Megaptera novaeangliae
• Online Access: https://hal.sorbonne-universite.fr/hal-01742720; https://hal.sorbonne-universite.fr/hal-01742720/document; https://hal.sorbonne-universite.fr/hal-01742720/file/Derville%20et%20al.%202018_JMAMM_preprint.pdf; https://doi.org/10.1093/jmammal/gyx185

International audience Maternal habitat preferences of humpback whales (Megaptera novaeangliae) are well documented from decades of coastal research but oceanic areas have received less attention. Whales breeding in New Caledonia occupy both ecosystems: a coastal reef complex (South Lagoon) and oceanic seamounts (Southern Seamounts). Generalized additive models were applied to 20 years of boat-based whale observations (n = 1,526) to describe habitat preferences and permissive home range estimations were used to explicitly model spatial segregation in relation to social context. Groups with calves (n = 206) preferred shallow coastal waters throughout the season in the South Lagoon, whereas no habitat segregation was observed between groups with (n = 74) and without calves (n = 140) in the Southern Seamounts. As a result, spatial overlap between groups with and without calves was more common in the Southern Seamounts than the South Lagoon. Despite a lack of social segregation around seamounts, mother-calf pairs were proportionally more frequent in the Southern Seamounts (27%) than in the South Lagoon (16%). Photographs of the calves’ dorsal flanks were analyzed to compare age and ecological markers across sites. Calves appeared older in the Southern Seamounts than in the South Lagoon but no difference in scarring or shark bites was found across sites, suggesting that calves experienced similar lifestyles and may move between offshore and coastal waters during the breeding season. This study highlights the flexible habitat-use patterns of breeding humpback whales and raises new questions about the environmental and social drivers of their presence in offshore breeding grounds.