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.
HŌ‘ULU‘ULU MANA‘O
I loko nō o ke kālailai nui ʻia ke ʻano ʻakeu o ka ʻohana naiʻa kai pāpaʻu a puni ka honua, ʻaʻole nō nui ka ʻike no ka pili nohona o nā koholā niho i ka moananuiākea. ʻO ka naiʻa nihoniho (Steno bredanensis), he naiʻa moana i ʻike nui ʻia a puni ka honua ma nā kai mahana a kopikala. Ma ka paeʻāina ʻo Hawaiʻi, loaʻa ʻelua pūʻuo ma ʻelua wahi kikoʻī: ʻo kekahi ma Kauaʻi me Niʻihau, a ʻo kekahi ma ka mokupuni ʻo Hawaiʻi. Ua noiʻi a kālailai mākou i ka ʻokoʻa ma ke ʻano o ka pilina ma waena o ia mau pūʻuo ma o ka ʻikepili kiʻi i ʻohi ʻia mai nā makahiki 2002-2020. Ma o ke kālailai i ke ʻano ʻakeu, ʻoi aku ka nui o nā māhele pūʻulu ma ka pūʻuo Kauaʻi me Niʻihau (i.e., ʻoi aku ka nui o ka hunahuna: 0.58 vs 0.47) ma mua o ka pūʻuo Hawaiʻi a ʻaʻole i like ka ikaika o ka hoʻohui (i.e., ke emi o ka ʻōnaehana hoʻohui: 0.07 vs 0.12). No ka ʻawelike o ka ikaika i loko o ia mau pūʻulu, ua ʻoi aku ka nui ma kahi o Hawaiʻi mokupuni (0.31) ma mua o ko Kauaʻi me Niʻihau (0.22). No nā pilina ʻakeu ma Hawaiʻi mokupuni, kālele nui ʻia ka heluna haʻahaʻa o nā naiʻa i mea e pili nā pūʻulu. Hāpai mākou i kēia manaʻo, kū nā ʻokoʻa o ka pili ʻakeu i ka nui o ka pūʻuo a me kahi e noho ai. I loko nō o ka hiki ʻole ke kikoʻī a māhuahua kā kuhikuhi i ke ʻano no ke emi o ka pākēneka e ʻike hou ʻia, ua hiki nō naʻe iā mākou ke ʻike a kālailai i nā ʻokoʻa o nā pili ʻakeu i waena o lāua.
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Citation:
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. doi: 10.1111/mms.70281
Link:
https://onlinelibrary.wiley.com/doi/10.1111/mms.70281