Food Habits of the Glossy Snake, Arizona elegans, with Comparisons to the Diet of Sympatric Long-Nosed Snakes, Rhinocheilus lecontei

Abstract

We studied the diet of the North American glossy snake, Arizona elegans, by examining stomach contents of more than 700 museum specimens, and supplemented our findings with published dietary records. Fifty percent of 107 prey were lizards and 44% were mammals; birds and snakes composed the remaining prey. Most lizard prey were diurnal, and presumably were captured when they were inactive by nocturnally wide-foraging glossy snakes. Conversely, most rodent prey were nocturnal heteromyids that we suspect were ambushed by A. elegans, thus raising the possibility that these snakes use alternative hunting tactics on different prey types. Ninety-five percent of the specimens with food contained a single item, and all 49 prey for which we determined direction of ingestion were swallowed head-first Although smaller A. elegans consumed mammals occasionally, specimens that ate mammals were significantly larger than those that fed on lizards, and glossy snakes that took birds were larger thap those that ate mammals. Larger glossy snakes ate larger prey and added birds to their diet, but they continued to eat lizards and mammals, which suggests that there is no absolute ontogenetic change in the diet of A. elegans. For any given body size, A. elegans has a longer head, and thus a larger gape than the sympatric long-nosed snake, Rhinocheilus lecontei. This difference in relative head length may explain why smaller A. elegans are capable of predation on mammals, whereas smaller R. lecontei feed almost exclusively on lizards, and may also account in part for the higher frequency of stout-bodied phrynosomatid lizards and of mammals in the diet of glossy snakes.