Effects of predation hazard on foraging "constraints": Patch-use strategies in grey squirrels [Sciurus cardinensis]

We examined the effects of predation hazard on patch-residence time and meal size (usually taken as foraging decisions), as well as on travel time, handling time, and the gain function (usually taken as constraints on foraging decisions). Each day we presented grey squirrels (Sciurus carolinensis) with eight artificial patches of sunflower seeds of the same initial density (either 25, 50, 100, or 200) at one distance to cover (either 5 or 15 m). We found that the squirrels ate the same quantity of seeds farther from cover, but that they ate them significantly faster. Squirrels also travelled significantly faster between patches, and handled seeds significantly faster within patches when farther from cover. The change in the handling times caused the squirrels' gain functions to be higher farther from cover. We found a predictable pattern of variation in the values of the presumed "constraints".