Meeting Abstract
Snakes are a model system for studying how anatomy affects feeding performance because their maximal gape constrains the size of prey that can be swallowed whole. However, maximal gape of snakes has rarely been measured directly. Despite having diverse diets, snakes rarely consume hard-bodied prey, yet crustacean specialists have evolved convergently in natricine and homalopsid snakes, which eat crayfish and crabs or shrimp, respectively. For the natricine Regina septemvittata, which eats only freshly molted crayfish, we tested how predator anatomy and prey size affected feeding performance and behavior by quantifying: 1) scaling relationships of maximal gape (N=25), 2) relative size of prey (prey area/ gape area) consumed in the field (N=145), and 3) effects of relative prey size on prey handling times and behavior during laboratory trials (N=107). For snakes with snout-vent lengths of 17-59 cm, maximal gape areas were 2.8-28.4 cm2 and had a scaling exponent (1.643; 95% CL =+0.373) not quite significantly less than geometric similarity (2). Of the field-caught snakes, 88% and 39% ate prey with relative sizes >50% and > 90%, respectively. During laboratory trials relative prey size predicted 45% of the variation in prey handling time. In 85% of trials the snakes held the prey and reduced its mobility before swallowing. For the same relative prey area, the predicted handling times of R. septemvittata are longer and shorter than those of the homalopsids that eat soft-shelled and hard-shelled crabs, respectively, but nearly identical to a homalopsid that eats snapping shrimp with a shape more similar to crayfish. These results nicely illustrate how predator anatomy, gape and behavior, and the size, shape and hardness of prey all have important consequences for feeding performance.
