Dear colleagues,

We are pleased to announce the recent publication of the following paper on the social structure of bottlenose dolphins:

Augusto, Joana F.; Rachinas-Lopes, Patricia; dos Santos, Manuel E. (2011). Social structure of the declining resident community of common bottlenose dolphins in the Sado Estuary, Portugal. Journal of the Marine Biological Association of the United Kingdom. doi:10.1017/S0025315411000889

Abstract:

The resident population of common bottlenose dolphins (Tursiops truncatus) in the Sado Estuary, Portugal, has been declining at least during the past three decades. A complete photographic census produced a current count of 24 animals—19 adults, three subadults and two calves. It appears to be phylopatric and essentially closed, but given the likely importance that exchanges with neighbouring coastal groups may play, even if rare, the most adequate term to deﬁne this dolphin should be community and not population. Large groups with all age-classes are common in the community, possibly as a calf and subadult protection strategy, and this may be related to the fact that these age-classes have had high mortality rates in the last decade. Maternity of two calves was determined, and we found that the two
mothers adopted different parenting strategies. While one mother spent more time alone with her calf, the other mother spent more time with her calf in larger groups. The average coefﬁcient of association for this community is 0.45, quite high for this species. Associations and typical group size are similar between all individuals, with no patterning according to age-class or sex, which constitutes an atypical trait for dolphin societies. There are also no clear divisions in this community according to cluster analysis. Associations are preferred and long term, lasting approximately 34 days and ﬁtting a pattern of casual acquaintances, where individuals associate for a period of time, disassociate and may reassociate after that. This reﬂects the ﬁssion–fusion character of the community, but in a more stable manner. We think this is caused by a combination of demographic characteristics and a stable and productive environment, which led to a decrease in competition between individuals.

Pdf copies are available upon request to augustojoana@gmail.com

Cheers,
Joana Augusto

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Joana Augusto, M.Sc.
PhD candidate
Whitehead Lab
Biology Dept.
Dalhousie University
Halifax, NS
B3H 4R2 Canada

http://whitelab.biology.dal.ca/

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