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 jaqu...@gmail.com
Nathalie Jaquet
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