Personality and environmental influences on the defensive behaviors and venom expenditure of six species of southern California rattlesnake

Martin, Chelsea                                                                                                                                       

cemartin@students.llu.edu

Department of Earth and Biological Sciences

Loma Linda University

Loma Linda, California USA

Herreria, Rosalynd                                                                                                                                        

Antelope Valley College                                                                                                                             

Lancaster, California USA

Hayes, William K.                                                                                                                                 

Department of Earth and Biological Sciences

Loma Linda University

Loma Linda, California USA

Environmental heterogeneity often causes variation in phenotypic traits, such as personality. Personality comprises behavior that is consistent across time and context and has been poorly studied in snakes compared to other groups. Little is known about how personality and environmental variation influence the behavior of rattlesnakes, a group that often experiences conflict with humans. The first of two studies examined whether personality influences the defensive behavior and venom expenditure of Crotalus helleri. Venom extractions of tube-restrained snakes biting membrane-covered beakers on three occasions showed that snake individual accounted for significant variation in number of strikes during tubing, latency to bite the membrane, total venom pulses, and venom quantity expulsed. Thus, individuals exhibited consistent tendencies (i.e., personality) in venom reliance. The second study assessed whether rattlesnakes from different habitats (coast, desert, mountain, and valley) exhibit dissimilar defensive behaviors during laboratory trials within open-field arenas in six southern California species (Crotalus atrox, C. cerastes, C. helleri, C. mitchellii, C. ruber, C. scutulatus). We hypothesized that snakes from habitats with greater vegetative cover and higher elevation would be less defensive due to decreased predation pressure. Preliminary results for C. helleri and C. ruber suggest that individuals exhibit consistent striking behavior between trials (i.e., personality). Crotalus helleri struck more frequently than C. ruber and gravid females stuck more than males and non-gravid females. Crotalus helleri from higher elevations and habitats with greater annual rainfall spent less time in defensive coils and struck less than snakes from lower elevations and areas with less annual rainfall. These preliminary results suggest that individual and species differences in behavior can be influenced by the environment. Analyses nearing completion for the remaining four species should shed further light. A better understanding of rattlesnake behavior could help to save snake lives and prevent human injury in the context of human-wildlife conflict.