We investigated variation in perceived foraging costs to kangaroo rats (Dip
odomys spp.) along a topographical gradient in the Chihuahuan desert. We us
ed resources left in experimental seed trays to assess these costs. Both th
e proportion of trays in which Dipodomys foraged and the giving up densitie
s of seeds in the trays decreased with elevation on hillside transects. The
se results suggest that kangaroo rat foraging activity was greater, with mo
re trays encountered, at the bottom of the hills; however, microhabitat for
aging costs (predation risks) were lower, yielding lower giving up densitie
s of seeds in trays, at the tops of the hills. (C) 2001 Academic Press.