HABITAT SELECTION AND PREY ODOR IN THE FORAGING BEHAVIOR OF WESTERN RATTLESNAKES (CROTALUS VIRIDIS)

We tested the roles of prey odor and other habitat cues in the pre-strike movement patterns of two, ecologically distinct sub-species of the western rattlesnake in naturalistic arenas. In the first experiment, rattlesnakes preferred habitat containing prey odor and cover comprised of rocks, sticks and plants. While searching, rattlesnakes methodically investigated the edges and crevices within rock, areas rodents might frequent in nature. In the second experiment, rattlesnakes investigated sticks more than rocks arranged topographically similar to sticks. In the third experiment, rattlesnakes preferred habitat that included brush foliage and used chemical prey trails in pre-strike behavior via (i) trail-following, (ii) casting search patterns and (iii) scanning search patterns. Several snakes coiled in stereotyped ambush postures that allowed them to face chemical trails while resting against rocks and foliage. These results suggest that rattlesnake foraging exhibits qualities advantageous for hunting rodent prey in addition to providing protection from predators and perhaps promoting thermoregulation. Sub-species did not exhibit geographic variation in foraging behavior despite differences in natural history and morphology. Hence, the microevolutionary pattern suggests that generalized foraging repertoires are successful in numerous environments when coupled with locally specialized body patterns.