Date of Award

Winter 1997

Project Type

Dissertation

Program or Major

Natural Resources

Degree Name

Doctor of Philosophy

First Advisor

John Litvaitis

Abstract

I studied the effects of variation in food patch quality and predation risk on the foraging patterns and measures of foraging behavior of New England (S. transitionalis) and eastern (S. floridanus) cottontails, and their survivorship and weight change during these experiments. I then superimposed the results of these experiments onto real habitat patches to determine the amount of habitat each species could occupy and maintain similar survivorship. Finally, I measured an adaptation (eye size), and predator detection of both species in an effort to explain the difference in survival between S. floridanus and S. transitionalis.

In outdoor enclosures (5.7 x 45.7-m) I manipulated food quality and predation risk among four food patches. I measured the give-up-density (GUD) of food at each feeder daily, and weighed animals on a weekly basis. I also developed a break-beam sensor device to measure the time cottontails spent foraging at feeders that in predation risk. Neither species varied their behaviors with predation risk, though S. transitionalis spent marginally more total time at risk. During this experiment when no food was available in cover, S. transitionalis had lower survival than S. floridanus. However, when food was available in cover, the survivorship curves of the two species did not differ. When food quality and predation risk varied among food patches, S. floridanus avoided the poorer quality patches and foraged at higher quality patches with greater predation risk, whereas S. transitionalis avoided only the poorest quality food patches. When I applied these foraging patterns onto real habitat patches I found that S. floridanus could occupy 99% of a habitat patch whereas S. transitionalis could only occupy 32% of a patch. As snow accumulated in winter, S. transitionalis lost a significant amount of suitable habitat whereas, S. floridanus did not. One mechanism that may explain the paradox in the survivorship and habitat use of the two species is the bulginess of their eyes and the distance that they can detect an approaching predator. S. floridanus has larger eyes, and can detect an approaching predator at a greater distance than S. transitionalis.

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