ABSTRACT
The drivers of animal social structures remain poorly understood, particularly in species such as cetaceans that are wide-ranging and challenging to study. Understanding the factors shaping sociality can shed light on population ecology, gene flow, and information transmission. Here, we investigated variation in social structure among three independent island-associated stocks of common bottlenose dolphins (Tursiops truncatus) around the main Hawaiian Islands. We generated social networks for each stock using photo-identification data from 2002 to 2022. We calculated modularity, density, degree centralization, and betweenness centralization to assess network structure. We measured the stocks’ available habitat and calculated their population densities. We also quantified association strength with the half-weight association index (HWI) and compared it within- and between-clusters, and by sex for each stock. HWIs revealed that within-cluster associations were much stronger than between-cluster in all stocks. Network modularity and HWI showed the lowest fragmentation into distinct clusters and the strongest associations in the smallest of the three habitats (Kaua‘i-Ni‘ihau). We found no conclusive evidence of sex differences in HWI. Our findings suggest that denser populations might drive social network fragmentation. Our study highlights the importance of further investigating the drivers of sociality.
HŌ‘ULU‘ MANA‘O
ʻAʻole maopopo leʻa nā mea e paipai ana i ka pili nohona holoholona, keu hoʻi ma nā lāhui koholā i noho i ʻō a i ʻaneʻi a i paʻakikī ko lākou kālailai ʻia ʻana. Ma o ka maopopo ʻana i ia mau mea e pā ana i ka pilina, hiki nō paha ke mōakāka iki mai ka pūʻuo kālai kaiaola, ka hoʻoili ōewe, a me ka hoʻōlapa ʻike. Ua kolokolo mākou i ka ʻokoʻa ma ka pili nohona o ʻekolu pūʻulu naiʻa nuku poko (Tursiops truncatus) kūʻokoʻa pili i nā mokupuni a puni ka paeʻāina Hawaiʻi. Ua hoʻokumu mākou i mau pūnaewele pilina no kēlā me kēia pūʻulu ma o ka ʻikepili hōʻoia kiʻi mai nā makahiki 2002–2022. Ua hoʻomaulia mākou i ka hoʻohui ʻana, ka paʻapū, ka nui o ka hoʻākoakoa ʻana, a me ka pilina o ka hoʻākoakoa ʻana i mea e kālailai aku ai i ka ʻōnaehana pūnaewele. Ua ana mākou i ka nui o ke kaianoho o nā pūʻulu a ua hoʻomaulia ʻia ka nui o ko lākou pūʻuo. Ua helu mākou i ka ikaika o ka pilina me ka papa kuhi o ka pilina hapa paona (HWI) a ua hoʻohālikelike ʻia i loko a i waena o nā pūʻulu, a ma ke keka o kēlā me kēia pūʻulu. Hōʻike ʻia ma nā HWIs, ʻoi loa aku ka ikaika o nā pilina i loko o nā pūʻulo ma mua o nā pilina ma waena o nā pūʻulu. No ka hoʻohui ʻana o ka pūnaewele a me ka HWI, ua hōʻike ʻia ka haʻahaʻa loa o ka ka hoʻohapa ʻana i nā ʻāhui kaʻawale a me ka ikaika loa o nā pilina ma ka liʻiliʻi loa o nā kainoho ʻekolu (Kauaʻi-Niʻihau). ʻAʻole i loaʻa iā mākou ka meheu paʻa no nā ʻokoʻa keka ma ka HWI. Ma o nā hua i loaʻa iā mākou, paipai nō paha nā pūʻuo nui i ka hoʻāpana ʻia ʻana o ka pūnaewele pilina. Kālele kā mākou kālailai i ke koʻikoʻi o ke kolokolo a noiʻi mau ʻana i nā mea e paipai ana i ka pili nohona.
Citation:
Corsi, E., R.W. Baird, A.E. Harnish, A.M. Gorgone, J.J. Currie, S.H. Stack, and J.J. Kiszka. 2025. Variation in Social Structure Among Multiple Stocks of Island-Associated Common Bottlenose Dolphins (Tursiops truncatus) in Hawaiian Waters. Marine Mammal Science: e70051. doi: 10.1111/mms.70051
Link:
https://onlinelibrary.wiley.com/doi/10.1111/mms.70051