Food habits of the glossy snake, Arizona elegans, with comparisons to the diet of sympatric long-nosed snakes, Rhinocheilus lecontei

We studied the diet of the North American glossy snake, Arizona elegans, by examining stomach contents of more than 700 museum specimens, and suppleme nted 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 the y were inactive by nocturnally wide-foraging glossy snakes. Conversely, mos t rodent prey were nocturnal heteromyids that we suspect were ambushed by A . elegans, thus raising the possibility that these snakes use alternative h unting tactics on different prey types. Ninety-Eve 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. eleg ans consumed mammals occasionally, specimens that ate mammals were signific antly larger than those that fed on lizards, and glossy snakes that took bi rds were larger than those that ate mammals. Larger glossy snakes ate large r 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 th e 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 hi gher frequency of stout-bodied phrynosomatid lizards and of mammals in the diet of glossy snakes.