Discrimination between envenomated and nonenvenomated prey by western diamondback rattlesnakes (Crotalus atrox): Chemosensory consequences of venom

Snake venoms have multiple consequences on prey, ranging from immobilizing and digestive effects to enhancing the salience of envenomated prey and the ir chemical trails. Although the? toxic and lytic effects are reasonably we ll understood, the chemosensory effects have been little studied. Experimen t 1 showed that western diamondback rattlesnakes (Crotalus atrox) preferred envenomated (E) over nonenvenomated (NE) prey in a standardized choice sit uation, as other species have done in previous studies. In Experiment 2, E prey were prepared by injecting reconstituted lyophilized venom, so that do sage could be controlled, something not possible when snakes envenomated pr ey as: in Experiment 1 and in most previous studies of rattlesnake response to E and NE prey Prey injected with 10 mg of lyophilized venom were reliab ly discriminated from NE prey by C. atrox A dose-response curve was establi shed in Experiment 3 to assess the lowest dose to produce E prey that were preferred over NE prey. Two statistical techniques were used to estimate mi nimum perceptible dose (MPD), giving values of 6.0 and 7.1 mg, respectively These values were compared with the amount of venom snakes actually inject ed during predatory strikes and with various measures of lethality. Chemose nsory effects of venom probably facilitate rattlesnake predatory behavior i n that adult rodents are usually released after envenomation, requiring tha t the snake follow the prey's trail to recover the carcass. This trail-foll owing task depends upon the snake's ability to discriminate trails of E pre y from those deposited in the vicinity by other (NE) rodents as they engage d in foraging activities.