Cues involved in relocation of struck prey by rattlesnakes, Crotalus viridis oreganus

Following release of an envenomated mouse, a rattlesnake begins a post-strike trailing behavior that allows it to track chemically and to recover the dispatched prey. The rattlesnake can discriminate the trail of the mouse that it struck from trails of other unstruck mice, suggesting that the struck mouse produces a chemically unique odor trail. The purpose of this study was to determine generally what those chemical cues might be and what emphasis the rattlesnake might give to each during post-strike trailing. Taking advantage of venomoid (venomless) rattlesnakes, four experiments were performed in which we examined the ability of rattlesnakes to discriminate trails of mice receiving fang punctures (but no venom), mice artificially struck by hand (no venom), different individual mouse scents, and the effects of venom on post-strike trailing ability. We found that fang puncture alone was sufficient to produce a distinctive odor trail, but that this was subordinate to the distinctiveness of individual mice odors; envenomated mice produced the most distinctive trail. Our results indicate that alone the mechanical effects of fang penetration of the integument produce a chemical uniqueness in the mouse, but that can be overridden by mouse odor and venom effects. Thus, rattlesnakes biting mice have available ranked odors unique to the struck mouse: venom > mouse odor > fang puncture.