VARIATION IN GIVING-UP DENSITIES OF FORAGING CHIPMUNKS (TAMIAS-STRIATUS) AND SQUIRRELS (SCIURUS-CAROLINENSIS)

We measured daily giving up densities (GUDs) of chipmunks and squirrels foraging for sunflower seeds embedded in a sand matrix over a ten week period. Our objective was to account for the variation in GUDs attributable to habitat, species, and rarely measured effects involving time (day sequence), temperature and site-to-site differences in forager densities. Results showed GUDs to be higher for: 1) open sites than under canopy; 2) a chipmunk only treatment than one with chipmunks + squirrels; 3) sites with few than many foragers; and 4) later than earlier periods of the study, particularly for the chipmunk only treatment on hot days. We attribute habitat related differences in GUDs to predation hazard that may be high in the open and lower under tree canopy, and species differences to body size and/or whether foragers were eating seeds directly or caching them. Multivariate analyses of foraging behavior, while not as focused as the more typical one-factor studies, provide an a posteriori means of understanding foraging in much of its complexity.