Strike-Induced Chemosensory Searching, Kleptoparasitism, and the Possibility of Chemical Crypsis in Rattlesnakes
Predator-prey interactions shape the natural histories of both species as each tries to adapt and counter-adapt to the tactics of the other. This important evolutionary dynamic is crucial for ecosystem formation and stability. Predation is a fundamental aspect of life for most organisms, and many venomous reptiles, particularly ambush-foraging viperids, have evolved a prey-acquisition strategy that is highly effective in immobilizing prey, while minimizing possible counterattacks. Best studied in rattlesnakes, this remarkable behavioral sequence is known as strike-induced chemosensory searching (SICS). Throughout decades of research, the body of SICS literature on venomous reptiles has become fairly robust, particularly in rattlesnakes. However, until now, there has never been a comprehensive review of this topic. In Chapter 1, I explore and discuss key results from decades of SICS research, which has mainly been conducted on rattlesnakes. I also provide a taxonomic overview of SICS in other species, and consolidate all known papers providing experimental tests of SICS into a convenient table. I organize the review topically, and also provide a summary section that provides forward-looking advice for future experimental work. During SICS, rattlesnakes partially rely on venom cues associated with prey trails, and a chemical search image of struck prey, to facilitate relocation of the carcass. However, rattlesnakes are also known to scavenge carcasses, although their propensity for such behavior remains unknown. In Chapter 2, I used captive rattlesnakes to conduct behavioral experiments to determine if rattlesnakes were more likely to locate and consume mouse carcasses if they had been envenomated by another snake. Such behavior would constitute an act of prey theft, known as kleptoparasitism. Results indicated that venom cues are not important to scavenging rattlesnakes, and that the striking of prey is necessary to facilitate efficient trailing behavior. Thus, kleptoparasitism might be an uncommon event in the wild, and scavenging behavior in rattlesnakes is difficult to generalize. Normally, however, rattlesnakes are ambush predators, and most species are small mammal specialists, mostly preying on rodents. Many rodent species have evolved numerous anti-predator defense mechanisms, and one such defense is detection and avoidance of predators via olfactory cues. However, it is likely that ambush-foraging viperids are not easily detected via chemoreception, and complete scent-suppression might be widespread in these snakes. This scent-suppression ability is known as chemical crypsis. Using more captive behavioral experiments in Chapter 3, I tested the ability of prairie voles to detect olfactory cues from two ambush-foraging viperid species and three active-foraging colubrid species. Vole behavioral responses, which were used as a proxy for stress indicators, were quantified during each treatment. The results did not reveal any significant differences in behavioral responses among treatments, rendering my assessment of chemical crypsis in rattlesnakes inconclusive. Voles likely were able to detect the snake scents, but individual responses to the odors were highly variable. Reasons for this response variation are discussed.
Ecology|Evolution and Development|Zoology
Teshera, Mark Scott, "Strike-Induced Chemosensory Searching, Kleptoparasitism, and the Possibility of Chemical Crypsis in Rattlesnakes" (2021). ETD Collection for University of Texas, El Paso. AAI28317743.