Factors influencing the foraging behavior of free-ranging rattlesnakes (Crotalus oreganus)

Putman, Breanna J.

Natural History Museum of Los Angeles and University of California

Los Angeles, CA USA

Clark, Rulon W.

Department of Biology

San Diego State University

San Diego, CA USA

Foraging is a key aspect of a species’ ecology and decisions made while foraging affect fitness in many ways. For snakes, ectothermic predators, both biotic (e.g., prey abundances) and abiotic (e.g., temperature) factors should influence hunting opportunities and thus their behaviors. Although much research has focused on snake foraging, only a handful of studies have detailed the behaviors of free-ranging individuals. We implanted temperature-sensitive radio transmitters in free-ranging northern Pacific rattlesnakes (Crotalus oreganus), and used fixed videography to record their foraging behavior. We took body temperature measurements of all snakes at hourly intervals and when snakes made notable movements (e.g., strike prey). We determined encounter rates with prey and strike rates on prey, distances moved between consecutive ambush sites, residency time at each site, and post-strike behaviors. We also examined whether body temperature influenced behaviors. Snakes encountered 4 prey/day; 90% of encounters were with California ground squirrels. Snakes typically did not stay at hunting sites for long and exhibited short distance movements to new sites. Snakes initiated strikes during 21% of all prey encounters, and 49% of these strikes were successful. Strikes were initiated at a wide range of temperatures and strike success was not largely affected by temperature. We also determined the temperature at which snakes started hunting activity each morning and retreated to refuge. Our findings indicate that variation in rattlesnake foraging behavior both within and between species may be driven largely by differences in habitat and prey abundances.