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A community split among dolphins: the effect of social relationships on the membership of new communities.

Nishita M, Shirakihara M, Amano M - Sci Rep (2015)

Bottom Line: Before the split, the males in the same community after the split more often associated with each other than they did with those in different community.These results indicate that the males of new community were socially different from the other males for a long time before the split, but the females might not have been different.The long-term social relationships among males could be maintained in the subsequent communities.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Fisheries and Environmental Science, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, JAPAN.

ABSTRACT
Little is known about community splitting among dolphins because such events are rare in dolphin populations. A case of a community split was confirmed in a population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Japan, where a group of approximately 30 dolphins moved to a new habitat some 60 km from the original habitat. We examined the associations among the dolphins before the community split to determine whether the new community members were already socially different before the split, using 7-year identification data. Before the split, the males in the same community after the split more often associated with each other than they did with those in different community. In contrast, the association patterns among females and between sexes showed no relationships with their post-split community membership. These results indicate that the males of new community were socially different from the other males for a long time before the split, but the females might not have been different. Our findings suggest that at time of the community split, the factors determining the memberships of the subsequent communities are sex-linked. The long-term social relationships among males could be maintained in the subsequent communities.

No MeSH data available.


Comparisons of the association indices (both HWI and HWIG) between sexes for each community class.(a) NC males-NC females vs. NC males-SC females (black bars) and SC males-NC females vs. SC males-SC females (white bars). (b) NC males-all females vs. SC males-all females. The individuals are classified into two community classes based on their post-split community memberships. The error bars represent the standard deviations. * indicates significance at P < 0.05 (Randomization test).
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f5: Comparisons of the association indices (both HWI and HWIG) between sexes for each community class.(a) NC males-NC females vs. NC males-SC females (black bars) and SC males-NC females vs. SC males-SC females (white bars). (b) NC males-all females vs. SC males-all females. The individuals are classified into two community classes based on their post-split community memberships. The error bars represent the standard deviations. * indicates significance at P < 0.05 (Randomization test).

Mentions: We compared the association indices of the NC males-NC females vs. those of NC males-SC females, as well as those of the SC males-NC females vs. those of SC males-SC females to examine whether the males tended to associate more often with females of the same community class as they did before the split. As shown in Fig. 5a, there were no differences in either the HWIs or HWIGs between the community classes of females for both the NC and SC males, indicating both the NC and SC males associated with the females, regardless of the females’ community class. Although this result showed that the males did not exhibit a preference for the females on the basis of post-split community memberships, the association indices of the NC males-all females were significantly greater than those of the SC males-all females in both the HWIs and HWIGs, indicating that the NC males associated with females more often than the SC males (randomization test, P = 0.0001, respectively, Fig. 5b).


A community split among dolphins: the effect of social relationships on the membership of new communities.

Nishita M, Shirakihara M, Amano M - Sci Rep (2015)

Comparisons of the association indices (both HWI and HWIG) between sexes for each community class.(a) NC males-NC females vs. NC males-SC females (black bars) and SC males-NC females vs. SC males-SC females (white bars). (b) NC males-all females vs. SC males-all females. The individuals are classified into two community classes based on their post-split community memberships. The error bars represent the standard deviations. * indicates significance at P < 0.05 (Randomization test).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4660307&req=5

f5: Comparisons of the association indices (both HWI and HWIG) between sexes for each community class.(a) NC males-NC females vs. NC males-SC females (black bars) and SC males-NC females vs. SC males-SC females (white bars). (b) NC males-all females vs. SC males-all females. The individuals are classified into two community classes based on their post-split community memberships. The error bars represent the standard deviations. * indicates significance at P < 0.05 (Randomization test).
Mentions: We compared the association indices of the NC males-NC females vs. those of NC males-SC females, as well as those of the SC males-NC females vs. those of SC males-SC females to examine whether the males tended to associate more often with females of the same community class as they did before the split. As shown in Fig. 5a, there were no differences in either the HWIs or HWIGs between the community classes of females for both the NC and SC males, indicating both the NC and SC males associated with the females, regardless of the females’ community class. Although this result showed that the males did not exhibit a preference for the females on the basis of post-split community memberships, the association indices of the NC males-all females were significantly greater than those of the SC males-all females in both the HWIs and HWIGs, indicating that the NC males associated with females more often than the SC males (randomization test, P = 0.0001, respectively, Fig. 5b).

Bottom Line: Before the split, the males in the same community after the split more often associated with each other than they did with those in different community.These results indicate that the males of new community were socially different from the other males for a long time before the split, but the females might not have been different.The long-term social relationships among males could be maintained in the subsequent communities.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Fisheries and Environmental Science, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, JAPAN.

ABSTRACT
Little is known about community splitting among dolphins because such events are rare in dolphin populations. A case of a community split was confirmed in a population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Japan, where a group of approximately 30 dolphins moved to a new habitat some 60 km from the original habitat. We examined the associations among the dolphins before the community split to determine whether the new community members were already socially different before the split, using 7-year identification data. Before the split, the males in the same community after the split more often associated with each other than they did with those in different community. In contrast, the association patterns among females and between sexes showed no relationships with their post-split community membership. These results indicate that the males of new community were socially different from the other males for a long time before the split, but the females might not have been different. Our findings suggest that at time of the community split, the factors determining the memberships of the subsequent communities are sex-linked. The long-term social relationships among males could be maintained in the subsequent communities.

No MeSH data available.