Steller sea lions range across the Pacific rim from Southern California in the east
to northern Japan in the west, where they have continuously occupied terrestrial
resting sites (haulouts) and breeding sites (rookeries) for hundreds of years, if
not longer. Why they choose (and stay) at these locations, and what their
preferred habitat is, remains unknown. Thus, two aspects of the Steller sea lion's
habitat usage were examined—the oceanographic and the terrestrial. For the
oceanographic aspect, spatial models were constructed to determine which
oceanographic factors are associated with haulouts and rookeries, and how
conditions near sites might differ from conditions elsewhere. The two modelling
techniques employed (logistic regression and supervised classification) were
evaluated using the kappa statistic (Kn o), and receiver-operating characteristic
(ROC) plots. Supervised classification was found to produce better-fitting models
than logistic regression.
In general, Steller sea lions showed preferences for sites associated with waters
that were relatively shallow, well-mixed, had higher average tidal speeds and
less-steep bottom slopes. Conditions within 1 nautical mile of land were better
predictors of haulout and rookery locations than were conditions within 10, 20,
and 50 nautical miles. No consistent differences were found in the physical
characteristics of waters surrounding sites in the eastern and western
populations of Steller sea lions, or between haulouts and rookeries.
Regarding the terrestrial aspect of their habitat, anecdotal accounts describe
Steller sea lions as predominantly occupying exposed, rocky shorelines, but this
habitat preference has never been quantified. Locations of haulouts and
rookeries were compared against a coastline type database to identify the
shoreline preferences of Steller sea lions and to look for other spatial trends in
site characteristics. Haulouts and rookeries were preferentially located on
exposed rocky shorelines and wave-cut platforms. No relationship was found
between either latitude or longitude of a site and its average non-pup count.
The results indicate that there are differences in both the oceanographic and
terrestrial characteristics of sites used by Steller sea lions versus areas of
coastline where they are not found. The models could be used to predict
changes in habitat use given changing physical conditions, and could be applied
to any central-place forager. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/16598 |
| Date | 05 1900 |
| Creators | Ban, Stephen S. |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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