[MARMAM] New article: The social organization of sperm whales in the Gulf of California and comparisons with other populations

Nathalie jaquet jaquetn at gmail.com
Tue Sep 15 08:13:28 PDT 2009


Dear all,

The following has now been published Journal of the Marine Biological  
Association of the United Kingdom.

Jaquet, N and Gendron D. (2009). The social organization of sperm  
whales  in the Gulf of California and comparisons  with other  
populations. Journal of the Marine Biological Association of the  
United Kingdom  89(5), 975 ­ 983.

ABSTRACT:
Intra-specific variation in social organization provides valuable  
insights into the selective forces driving social evolution.
Sperm whales are distributed globally and live far from shore, thus  
obtaining large sample sizes on social organization in
multiple areas is logistically challenging and few comparative  
studies exist. In order to address how ecological factors influence
sociality, we investigated the social organization of sperm whales in  
the Gulf of California (GoC) using a long-term study
(1998 ­ 2004) and compare our results to other published studies.  
Standard photo-identification and behavioural observation
techniques were used. Group size was calculated from photographic  
mark ­ recaptures using a Petersen estimator. Social
organization was investigated using SocProg 2.3. Mean typical group  
sizes in the GoC were similar to those in the
Gala  pagos Islands, Chile and Seychelles (24.7, 24.8, 30.4 and 18  
individuals respectively), but substantially larger than in
the Sargasso Sea, Caribbean and northern Gulf of Mexico (12.0, 6.4  
and 6.9 individuals respectively). Sperm whale social
organization in the GoC best fitted a constant companion/casual  
acquaintance model, where permanent units sizes were
12.5 individuals and two units usually associated together to form a  
group. This structure is similar to the situation in
the Galapagos Islands and Chile areas. However, groups were more  
stable in the GoC than in the South Pacific, as groups
stayed together for periods of about 80 days versus about ten days in  
the Galapagos Islands and Chile. It is likely that differ-
ences in the social organization between the study areas in the  
Pacific and Atlantic Oceans were due to differences in preda-
tion pressure and/or food resources. We suggest that, site-specific  
ecological factors are likely to influence fundamental aspects
of sperm whale social organization.

pdf reprints are available upon request at jaquetn at gmail.com

Nathalie Jaquet
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