[MARMAM] New paper on the social structure of resident bottlenose dolphins

Joana Augusto augustojoana at gmail.com
Sun Oct 23 06:32:13 PDT 2011

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


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 at gmail.com

Joana Augusto

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


Let's Talk Science Coordinator
Dalhousie University
LTS at dal.ca

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