Safety in coils: predation rates of ambush hunting rattlesnakes are extremely low

Rattlesnakes are widespread mesopredators that are themselves killed and eaten by a host of other predators, including birds of prey and carnivorous mammals. Although anecdotal accounts of rattlesnake depredation are common, there are few quantitative data on encounter rates between rattlesnakes and their predators. Here we review a large database of encounters between rattlesnakes and their predators recorded from field videography of snakes in the sit-and-wait phase of their ambush hunting strategy. We found that, across 8300 hours of observation, adult rattlesnakes of six species and multiple populations exhibit low encounter rates with predators; furthermore, when predators were encountered, we never observed them to attack or kill coiled snakes. Thus, we propose that rattlesnakes are preyed upon while performing other, riskier behaviors associated with moving through the landscape. We also discuss why rattlesnakes are at low risk of predation while hunting on the surface.

Suitability of day-old chicks as food for captive snakes

Snakes are increasingly kept by private hobbyists and their numbers in the pet trade are increasing. Since suitable diets are essential for the health, welfare and maintenance of captive animals, objective research is required to improve and evaluate current feeding practices. Unfortunately, the husbandry of reptiles is frequently led by tradition, resulting in methods which are not evidence based. One such occurrence is the widespread belief that day-old chicks (DOCs) are unsuitable as food for captive snakes. Since this assumption has not been systematically assessed, herein I review the evidence in order to provide a more informed basis from which to evaluate the suitability of chicks in relation to rodent prey. Commonly expressed nutritional, ecological and husbandry-related concerns are examined using compilations of previously published data, new data, prior experience and nutrient compositions obtained from the Zootrition™ database. Day-old chicks were compared with two rodent species (mice and rats) since these are the most commonly used alternative prey item. Rodents were clearly the better option only in their 'naturalness', in that mammalian prey species are more frequently represented in natural diets than birds. I conclude that DOCs are a suitable prey item for snakes in captive collections since the available data provide no firm evidence for their avoidance, contrary to popular belief. Many gaps in our knowledge remain that would assist further discussion of this issue, and these are highlighted within. It is pertinent that although these data indicate that DOCs are a viable alternative to rodent prey for captive snakes, they do not necessarily indicate its superiority. In most instances, rodents and DOCs may be regarded as practically equivalent and interchangeable. It is therefore the individual keeper's preference as to which to use, informed in particular circumstances by the information presented herein.

Feeding ecology of the Great Basin Rattlesnake (Crotalus lutosus, Viperidae)

Documenting variation in organismal traits is essential to understanding the ecology of natural populations. We relied on stomach contents of preserved specimens and literature records to assess ontogenetic, intersexual, temporal, and geographic variations in the feeding ecology of the North American Great Basin Rattlesnake ( Crotalus lutosus Klauber, 1930). Snakes preyed mainly on rodents, occasionally on lizards, and less frequently on birds; squamate eggs and frogs were rarely eaten. There was a positive relationship between predator and prey size. The best predictors of this relationship were prey diameter as a function of snake body length and head size, underscoring the importance of prey diameter for gape-limited predators such as snakes. Crotalus lutosus displayed ontogenetic, sexual, and seasonal variations in diet. Smaller rattlesnakes fed predominantly on lizards, whereas larger individuals mostly fed on mammals. Females fed on lizards more often than males. The proportion of mammals in the diet was highest during the summer, a temporal variation that may be related to behavioral shifts in the diel activity and prey selectivity of C. lutosus, and (or) to differential abundance of rodents between seasons. Great Basin Rattlesnakes also displayed geographic variation in feeding habits, with snakes from the Great Basin Desert eating a higher proportion of lizards than serpents from the more northern Columbia Plateau.