[MARMAM] two new papers on California sea lions

Manuela Gonzalez Suarez manuela.gonzalez at asu.edu
Tue Dec 9 13:56:55 PST 2008

Dear colleagues,

Two new papers on California sea lions have been recently published. You can
send PDF requests to: manuela.gonzalez at asu.edu

 1) Manuela Gonzalez-Suarez and Leah R, Gerber (2008) Habitat preferences of
California sea lions: implications for conservation. *Journal of Mammalogy*,
*Abstract**.* California sea lions (*Zalophus californianus*) occur along
much of the Pacific coast of North America, but the number of breeding areas
that are occupied is relatively small. Our understanding of the attributes
that make these few sites preferable is currently limited. We quantified
habitat characteristics—substrate type and coloration, aspect, slope,
curvature of shoreline, and availability of shade, water pools, and resting
areas—at 26 sites (7 islands) occupied by sea lions and 33 unused sites (8
islands) distributed throughout the Gulf of California, Mexico. Logistic
regression models were used to explore how habitat characteristics explained
sea lion occupancy patterns. Models discriminated very well between occupied
and unused sites, and showed that occupied locations were more often located
in sites with larger-size rocks (odds ratio [OR] = 1.209), lighter-color
substrates (OR = 0.219), and convex shorelines (OR = 1.067). All of these
preferred characteristics are likely to play a role in the prevention of
heat stress in sea lions, suggesting that increases in temperature, such as
those expected from global warming, may pose an additional risk for this
already declining sea lion population. To partially offset this risk, our
results may be used to identify, and protect, unused but suitable (i.e.,
thermally favorable) habitat. In addition, we recommend effective protection
and monitoring of the currently occupied areas and their populations.

2) Manuela Gonzalez-Suarez and Leah R, Gerber (2008). A behaviorally
explicit demographic model integrating habitat selection and population
dynamics in California sea lions. *Conservation Biology* 22:1608-1618
*Abstract**. *Although there has been a call for the integration of
behavioral ecology and conservation biology, there are few tools currently
available to achieve this integration. Explicitly including information
about behavioral strategies in population viability analyses may enhance the
ability of conservation biologists to understand and estimate patterns of
extinction risk. Nevertheless, most behavioral-based PVA approaches require
detailed individual-based data that are rarely available for imperiled
species. We present a mechanistic approach that incorporates spatial and
demographic consequences of behavioral strategies into population models
used for conservation. We developed a stage-structured matrix model that
includes the costs and benefits of movement associated with 2
habitat-selection strategies (philopatry and direct assessment). Using a
life table for California sea lions (*Zalophus californianus*), we explored
the sensitivity of model predictions to the inclusion of these behavioral
parameters. Including behavioral information dramatically changed predicted
population sizes, model dynamics, and the expected distribution of
individuals among sites. Estimated population sizes projected in 100 years
diverged up to 1 order of magnitude among scenarios that assumed different
movement behavior. Scenarios also exhibited different model dynamics that
ranged from stable equilibria to cycles or extinction. These results suggest
that inclusion of behavioral data in viability models may improve estimates
of extinction risk for imperiled species. Our approach provides a simple
method for incorporating spatial and demographic consequences of behavioral
strategies into population models and may be easily extended to other
species and behaviors to understand the mechanisms of population dynamics
for imperiled populations.


"I have never let my schooling interfere with my education"
Mark Twain
Manuela Gonzalez
SOLS Biology Graduate Program
P.O Box 874601 ASU Tempe, AZ 85287-4601
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