Meeting Abstract
Snakes are a classic example of a gape-limited predator, but ironically gape has been quantified directly in fewer than 10 of more than 3,500 extant species. Besides an anatomy specialized for large gape, snakes seem likely to require additional specializations for unusual types prey, such as crustaceans. In this study, we quantified maximum gape and its scaling relationships for two natricine snake species (Regina septemvittata, Liodytes alleni) that primarily prey upon freshly molted (soft) or hard-shell crayfish, respectively. We also quantified the relative area (RelA) of prey consumed in the field and in the lab as a percentage of the maximal cross-sectional area of snake gape. For snakes with equal snout-vent length, the maximal gape of L. alleni (N=26) was significantly larger than that of R. septemvittata (N=21). In the field, R. septemvittata (N=148) consumed large prey (RelA>50%) more often than L. alleni (N=17) (38% vs. 22% of stomach contents). For equal RelA during laboratory trials, L. alleni consumed soft-shell prey significantly faster than hard-shelled prey. However, presumably as a result of its coiling behavior, L. alleni consumed soft-shell crayfish significantly faster than R. septemvittata. In laboratory trials of L. alleni, when prey exceeded 50% RelA the success rates of attacks were 11% and 48% for hard-shelled (N=19) and soft-shelled (N=42) crayfish, respectively. Similar to the two natricine study species, the Southeast Asian snake that eats hard-shell crabs has larger gape but eats prey with smaller relative size than its sister species that eats only soft-shell crabs. Hence, the primary constraints of snakes for the maximal prey size when eating hard-shell and soft-shell crustaceans are probably the ability to capture prey and maximal gape, respectively.
