The presence of distinct social groups within an animal population can result in heterogeneity in many aspects of its life history and ecology. The ability to accurately assess social group membership increases with the number of times individuals are identified, but obtaining sufficient sightings of rarely-encountered species can be difficult. Three social clusters were previously identified for the endangered population of false killer whales Pseudorca crassidens around the main Hawaiian Islands, using modularity among associations within a 12-year photographic dataset with no restrictions on the number of times seen. In this study, we used photo-identification data over a 23-year period to reassess the number and membership of social clusters within the population, restricting analyses to individuals seen on at least five different days. We compared the robustness of clustering assignments from six community detection algorithms using modularity and found that the three highest-ranking algorithms all identified the same number (four) and membership of social clusters. Spatial use of clusters varied among the islands, with three of the four clusters encountered regularly only off one or two of the three main island study areas. Comparison of genetic differentiation between social clusters revealed significant differentiation in nuclear DNA among clusters. Furthermore, all individuals in two of the clusters possess the same mitochondrial DNA haplotype, while in the other two clusters approximately 40% of animals possess a second haplotype. This level of clustering and associated heterogeneity within the population may have implications for mark-recapture abundance estimation, as well as for mitigating exposure to anthropogenic activities, including interactions with fisheries.
Pili nā ʻano like ʻole o ka nohona a me ke kālaikaiaola o nā pūʻuo holoholona i ka loaʻa ʻana o nā pūʻulu kikoʻī. Piʻi aʻe ka hiki ke helu kūponoʻia ka māhuahua ʻana o nā heluna o ia mau pūʻulu i ka helu ʻana i nā wā e ʻike ʻia ai kēlā me kēia holoholona, ʻo ka lawa ʻana naʻe o ka ʻike ʻana i nā lāhulu ʻane halapohe kekahi ālaina. Hōʻia ʻia ʻekolu pūʻulu o ke koholā ʻane halapohe, ʻo ka Pseudorca crassidens, a puni nā mokupuni nui ʻewalu o Hawaiʻi, ma ka hoʻowaeʻanona ʻana i ka pilina i loko o kekahi ʻikepili kiʻa he ʻumikūmālua makahiki me ke kāohi ʻole i ka nui o ka ʻike ʻia ʻana. Ma kēia kilo ʻana, ua hoʻohana mākou i ka ʻikepili ma o nā makahiki he iwakāluakūmākolu i mea e hōʻoia hou ai i ka heluna a me nā lālā o nā pūʻulu launa i loko o kekahi pūʻuo holoholona, a pāpā ʻia nā kālailaina i nā mea i ʻike ʻia ma ʻelima mau lā ʻokoʻa ma ka liʻiliʻi loa. Hoʻohālikelike mākou i ke ʻano me ka ikaika o kēia mau pūʻulu launa ma ka hoʻohana ʻana i ka hoʻowaeʻanona ʻana ma ʻeono pūʻulu haʻilula a ʻo ka mea i loaʻa, ʻo ia hoʻi ka ʻike ʻana, ma o nā haʻilula nui ʻekolu, i ka heluna a me ka lālā hoʻokahi o nā pūʻulu launa. Loli ka hoʻohana ʻana i ke koana o nā pūʻulu ma waena o nā mokupuni, ʻike ʻia ʻekolu pūʻulu ma hoʻokahi a ʻelua paha mokupuni mai loko mai o nā mokupuni nui ʻekolu e kālailai ʻia ana. Ma ka hoʻohālikelike ʻana aku i nā hiʻohiʻona ōewe ʻokoʻa o nā pūʻulu launa, ʻike ʻia ka ʻokoʻa ʻano nui ma ka piko ōewe o nā pūʻulu. A no laila, loaʻa i nā mea a pau o ia mau pūʻulu ʻelua ke ōewe hoʻoilina hoʻokahi, a ma nā pūʻulu ʻē aʻe ʻelua, loaʻa he hiʻohiʻona ōewe ʻelua i nā holoholona he 40 pākēneka. Hiki nō paha i kēia ʻano hoʻopūʻulu ʻana me kēia ʻano waeʻanona ōewe hoʻopili ma kekahi pūʻuo ke pili i ke kuhi ʻana i ka nui ma ka hopu kaha ʻana, a i ke kāohi a hoʻēmi ʻana mai i nā hopena o nā hana kanaka, e laʻa hoʻi me ka hana ma ke kai lawaiʻa.
Mahaffy, S.D., R.W. Baird, A.E. Harnish, T. Cullins, S.H. Stack, J.J. Currie, A.L. Bradford, D.R. Salden, and K.K. Martien. 2023. Identifying Social Clusters of Endangered Main Hawaiian Islands False Killer Whales. Endangered Species Research 51:249-268 doi: 10.3354/esr01258Download PDF
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