New publication on rough-toothed dolphin social network structure: Corsi, E., R.W. Baird, S.D. Mahaffy, J.J. Kiszka. 2026. Social life in the deep: variation in network structure and association patterns of rough-toothed dolphins (Steno bredanensis) around the main Hawaiian Islands. Marine Mammal Science 42:e70281. https://doi.org/10.1111/mms.70281
Abstract While coastal delphinid sociality has been extensively investigated across the globe, little is known about the social structure of odontocetes in the open ocean. The rough-toothed dolphin (Steno bredanensis) is a globally distributed oceanic dolphin occurring in tropical and warm-temperate waters. Around the main Hawaiian Islands, two demographically distinct populations have been identified: one off Kauaʻi and Niʻihau, the other off Hawaiʻi Island. We investigated differences in network structure and association patterns between these populations using photo-identification data collected from 2002-2020. Social network analysis revealed that the Kauaʻi–Niʻihau population was more subdivided into distinct social clusters (i.e., had higher modularity: 0.58 vs. 0.47) and less densely interconnected (i.e., lower network density: 0.07 vs. 0.12) than the Hawaiʻi Island population. Mean association strength within clusters was higher off Hawaiʻi Island (0.31) than off Kauaʻi–Niʻihau (0.22). Social connections off Hawaiʻi Island also relied more strongly on a smaller number of individuals that linked clusters together. We suggest that differences in population density and habitat extent may contribute to differences in social network structure. Although low re-sighting rates limited our ability to characterize either population comprehensively, applying identical methods allowed us to identify relative differences in network structure between them. If you would like a pdf contact Enrico Corsi ([email protected]<mailto:[email protected]>) or myself. For more on what Cascadia Research does check out our end-of-summer wrap-up flipbook https://cascadiaresearch.aflip.in/Summer_2026.html -- Robin W. Baird, Ph.D. Hawai‘i Program Director Cascadia Research Collective<https://cascadiaresearch.org/> 218 ½ W. 4th Avenue Olympia, WA 98501 USA https://orcid.org/0000-0002-9419-6336 Donate to support our work<https://cascadiaresearch.org/donations/> Follow us on Facebook<https://www.facebook.com/CascadiaResearch/> Updates from our August Kaua‘i field project<https://cascadiaresearch.org/hawaii-update/august2026/> Recent publications<https://cascadiaresearch.org/hawaii_publications/>: Baird, R.W. 2026. Dwarf and pygmy sperm whales Kogia sima (Owen, 1866) and Kogia breviceps (de Blainville, 1838). Pages 313-352 in Ridgway and Harrison's Handbook of Marine Mammals, Volume 3 River Dolphins and Larger Toothed Whales. Edited by T.A. Jefferson. Academic Press Elsevier. Corsi, E., R.W. Baird, S.D. Mahaffy, and J.J. Kiszka. 2026. Social life in the deep: variation in network structure and association patterns of rough-toothed dolphins (Steno bredanensis) around the main Hawaiian Islands. Marine Mammal Science 42(4):e70281. https://doi.org/10.1111/mms.70281 Harnish, A.E., R.W. Baird, and M.A. Kratofil. 2026. Diving behavior of common bottlenose dolphins around the main Hawaiian Islands: individual variation and responses to diel and lunar cycles. Marine Mammal Science 42:e70232. https://doi.org/10.1111/mms.70232 Kratofil, M.A., J.F. Shaff, H.K. Hoffbauer, M. Cantor, M.C. Hill, and R.W. Baird. 2026. Ecological contexts of diving behavior in Hawaiian false killer whales. Movement Ecology https://doi.org/10.1186/s40462-026-00630-4
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