| I explored phasic (immediate) and tonic (temporally extended) aspects of antisnake behavior in rock squirrels (Spermophilus vareigatus), focusing on the following questions: (1) Does antipredator behavior, during and after a predator encounter, vary with both immediate danger and temporal persistence of threat from the predator? (2) Is there a relationship between experience with predators and deployment of antipredator behavior in phasic and tonic time frames?; To explore the roles of immediate and persistent predatory threat in antipredator behavior, I presented adults and juveniles with rattlesnakes (Crotalus atrox) and gopher snakes (Pituophis melanoleucus ). Rattlesnakes are venomous ambushers and hence pose a greater and more tonic threat than nonvenomous, actively-foraging gopher snakes. Adults differentiated snake species, responding with greater efficacy to the more dangerous rattlesnake, and persisting in their antipredator behavior for longer after rattlesnake than gopher snake encounters, thus differentiating both levels and temporal features of threat. The absence of such snake-species differentiation by juveniles suggests a role for experience in this system.; Experience with predators was associated with rock squirrel antisnake behavior in multiple time frames. In the longest time frame, an urban population that had been relatively snake-free for a century was compared to a wilderness population under current snake predation. The wilderness population apparently matched the phasic and tonic features of risk more closely, displaying less arousal during and after a rattlesnake encounter than the urban population, but persisting longer. In an intermediate time frame, differentiation between rattlesnakes and gopher snakes changed in the urban population after experimental exposure to snakes intermittently at four-year intervals. Snake-species differentiation was not present during the first year (Owings et al. 2001), but emerged during the fourth. In the shortest time frame, the order of snake-species presentations was important; squirrels receiving rattlesnakes first differentiated snake species, those receiving gopher snakes first did not.; Paradoxically, urban squirrels were more cautious under baseline conditions than wilderness squirrels, despite a relatively snake-free environment, so I examined additional, non-snake differences between the populations. Urban squirrels exhibited more baseline caution possibly because they had more pups nearby and were less habituated to humans than wilderness squirrels. |
