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Research Letters in Ecology
Volume 2008, Article ID 498390, 5 pages
Research Letter

Shared Reproductive State Enhances Female Associations in Dolphins

Marine Mammal Research Group, Graduate School of the Environment, Macquarie University, NSW 2109, Australia

Received 9 July 2007; Accepted 27 December 2007

Academic Editor: Daniel I. Rubenstein

Copyright © 2008 Luciana M. Möller and Robert G. Harcourt. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Female bottlenose dolphins (genus Tursiops) usually associate at moderate level with other females within social clusters called bands or cliques. It has been suggested that reproductive state may play the predominant role in determining associations within female T. truncatus bands. Here, we test the hypothesis that reproductive state correlates with associations of female Indo-Pacific bottlenose dolphins (T. aduncus). We found that females in similar reproductive state, which included females from late pregnancy to the first year of their calves' life or females from early pregnancy to their calves' newborn period, had higher-association coefficients with each other than they did with females in different reproductive states (females with older calves or without calves). This was observed both within and across social clusters suggesting that reproductive state, at least for pregnant females and those with young calves, plays an important role in determining who to associate with. However, a female's most frequent associate was not always with another in similar reproductive state. We suggest that several factors, including reproductive state, may be of importance in determining associations of female bottlenose dolphins.