[MARMAM] new publication available on Guiana dolphins

Marcos Santos sotalia at gmail.com
Fri Aug 27 14:57:40 PDT 2010

Dear marmamers:

The following manuscript on Guiana dolphins displaying the beach hunting
behavior has recently been published in the Brazilian Journal of
Oceanography (see abstract below): Santos, M. C. de O. (2010) Guiana
dolphins (Sotalia guianensis) displaying beach hunting behavior in the
Cananeia estuary, Brazil: social context and conservation issues. Brazilian
Journal of Oceanography, 58(2): 143-152.

Requests will be attended at: sotalia at gmail.com

Marcos Santos

To elaborate a fuller description of the beach hunting behavior displayed by
Guiana dolphins (*Sotalia guianensis*) in the Cananéia Estuary (CE) (25oS,
48oW), a photo-identification study was conducted from May 2000 to July
2003. Three land platforms were chosen at the main entrance of the
abovementioned estuary, where scientists enjoy a unique opportunity to
observe dolphins at greater proximity, undisturbed. Observations were
opportunistic and unevenly distributed in time and space. In 67 days of
surveys, rendering approximately 80h of direct observations, 4,102
photographs were taken, of which 1,098 (26.8%) were considered useful for
identification purposes. A total of 103 groups were reported (3.7 ± 2.6
individuals), ranging from solitary dolphins to 15 individuals. Female-calf
pairs were observed in 92.4% of all the groups investigated. On the first
occasion, a calving interval was observed for the species in the CE:
approximately 3 years and 9 months. Of the 40 individuals identified at
least once, eleven used the sloping beaches regularly: females KN #s 10, 30,
255, 268 and 279; males KN #s 86 and 257; and four individuals of unknown
sex. The characteristics of the associations among beach hunters were
evaluated by the analyses of association indices. A total of 83 possible
associations between dyads were analyzed using the half-weight index and two
selective criteria (5+ and 8+ sightings/individual). Mean association
indices varied from 0.12 to 0.16, evidencing weak bonds among beach hunters.
Most regular beach hunters were females, showing that the beach hunting
behavior should probably be considered more typically female. Beach hunting
in the CE might be considered another example of cultural transmission in
cetacean societies.

Dr. Marcos César de Oliveira Santos

Projeto Atlantis, Laboratório de Biologia da Conservação de Cetáceos
Programa de Pós-Graduação em Zoologia, Departamento de Zoologia, Instituto
de Biociências,
Universidade Estadual Paulista "Júlio de Mesquita Filho" (UNESP), Campus Rio
Av 24-A, 1515, Bela Vista, Rio Claro, SP, Brasil, 13506-900.
Tel: 55-19-3526-4296
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