[MARMAM] New paper on Sex differences in residency patterns of Risso's dolphins

marc fernandez marc.fern at gmail.com
Wed Apr 8 02:44:18 PDT 2015

Dear colleagues,

We are pleased to announce a new paper describing the differences we found
in residency patterns for males and females Risso's dolphins.

A PDF version of the paper is available online at:
http://onlinelibrary.wiley.com/doi/10.1111/mms.12209/abstract or via email
request to: oceanwatch at gmail.com

Hartman, K. L., Fernandez, M., Wittich, A., & Azevedo, J. M. N. (2015). Sex
differences in residency patterns of Risso's dolphins (Grampus griseus) in
the Azores: Causes and management implications. *Marine Mammal Science*.


Knowledge of the residency patterns of marine mammals is an important
element for management and conservation strategies. Here we investigate a
population of Grampus griseus off Pico Island, Azores. Our data set covers
the period 2004–2007, based on at-sea observations of 1,250 individually
identified animals, 303 of known or assumed sex. Using photo identification
and GPS locations we calculated mean monthly sighting rates and lagged
identification rates to analyze temporal patterns, and estimated kernel
density to study the home range. Our results show site fidelity and
relatively restricted home ranges, which corroborate the existence of a
resident population on the study site. We further document sex differences,
including a higher number of males present in the area at any given time
but females staying for longer consecutive periods, and male home ranges
with significantly less overlap than those of females. These observations
are consistent with a mating system based on multimale pods defending areas
where females periodically return. We hypothesize that squid distribution
is a major factor in structuring these patterns. These findings reinforce
the need for a precautionary management approach that would include
limiting pressure from commercial activities.


Marc Fernandez
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