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1 March 2009 Does Prey Availability Determine Seasonal Patterns of Habitat Selection in Texas Ratsnakes
Jinelle H. Sperry, Patrick J. Weatherhead
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An animal's requirements (e.g., food vs. shelter) from its environment are likely to vary seasonally and, therefore, so too should habitat selection. Here, we test the hypothesis that Texas Ratsnakes (Elaphe obsoleta) choose habitats based on prey availability during their active season and on cover during winter. We examined snake habitat selection at three spatial scales and compared that to abundance of small mammals and nesting birds, which we confirmed by diet analysis to be the snakes' principal prey. Small mammal trapping and avian point counts showed that overall prey abundance was higher on mesas and slopes compared to savannahs. Compared to availability of habitats within the entire study area, snakes selected home ranges with a high proportion of slope habitat. Within home ranges, however, selection for slopes was exhibited only during winter when foraging is at a minimum and snakes are relatively inactive. Snakes did not use habitat within home ranges selectively during the active season or during the avian breeding season. The latter result suggests that ratsnakes are effective avian nest predators despite preying on birds opportunistically. However, it is also possible that some individual ratsnakes specialize on birds, whereas the majority preys on mammals. Microhabitat analysis comparing winter and active season sites showed that snakes preferentially used areas of high canopy cover and rock ground cover during winter. Collectively these results provide limited support for the hypothesis that ratsnakes use habitats based on prey availability but do indicate that ratsnakes select winter habitat based on cover availability.

Jinelle H. Sperry and Patrick J. Weatherhead "Does Prey Availability Determine Seasonal Patterns of Habitat Selection in Texas Ratsnakes," Journal of Herpetology 43(1), 55-64, (1 March 2009).
Accepted: 1 June 2008; Published: 1 March 2009

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