Airborne Chemical Information and Context-Dependent Post-Strike Foraging Behavior in Pacific Rattlesnakes (Crotalus oreganus)

Predators demonstrate context-dependent foraging behaviors to dynamically and successfully track prey and can use multiple cues in this process. In squamate reptiles (snakes and lizards), chemical signals from prey significantly influence predatory behavior, especially substrate and airborne cues. In this study, we examined behavioral variation in rattlesnakes (Crotalus oreganus) during strike-induced chemosensory searching (SICS), a sterotyped complex of behaviors seen in squamates. Rattlesnakes can use both substrate and airborne chemical cues during SICS, but we sought to determine the changes during SICS when either substrate, airborne, or air-deposited chemical cues were the only types available to snakes in a Y-maze. We hypothesize that these cues represent the spectrum of chemical information available in the natural environment. We also modified scoring of choice in the Y-maze by deriving a choice penalty score, a reflection of how extensively the snake explored the unscented arm of the maze. In the presence of substrate trails, rattlesnakes relocated prey fastest, had highest rates of tongue-flicking, and received the lowest choice penalty scores during SICS. Airborne chemical cues enabled successful relocation, but rattlesnakes took longer to relocate prey, increased the frequency of many searching behaviors, and more extensively explored the Y-maze (more negative choice penalties). When air-deposited cues were the only type available, rattlesnakes took the longest to choose an arm, had the lowest rates of tongue-flicking, and backtracked most often. We suggest that as prey odor becomes more dilute, rattlesnakes demonstrate behavioral plasticity in SICS to preserve their ability to relocate prey.