Evaluating habitat suitability for tree squirrels in a suburban environment.
1996
Andrew Alek Tuen | Brown Joel S.
Measuring an animal's use of food patches can reveal its perceptions of safety, food availability, and its own well-being in both disturbed and pristine habitats. In this paper we use foraging theory and patch-use technique to evaluate the response of tree squirrels (Sciurus niger) to patch richness, food quality and predation risk in a disturbed habitat in suburban Chicago. Giving up densities (GUDs) were measured in food patches containing 9, 18 and 27 gm of sunflower seeds to evaluate response to patch richness. Response to food quality was studied by measuring GUDs in patches containing seeds which had been treated with oxalate and tannins. Predation risk was varied by placing the food patch at the base and three meters away from the base of a tree. Tree squirrels responded to food abundance by biasing their foraging activity towards rich patches and equalized GUDs among food patches. Oxalate significantly reduced the value of the food resulting in higher GUDs compated to tannins. Microhabitat differences in GUDs indicated that foraging away from a tree posed a higher predation risk to squirrels than foraging near a tree. We conclude that appropriate and careful measurements of GUDs can reveal an animal's perception of habitat quality, food characteristics and predation risk.
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