Feeding performance in the Western Ribbon Snake (Thamnophis proximus): ontogeny and the effects of prey type and size

Abstract

It has been suggested that juveniles have exaggerated morphologies or improved performance to compensate for the disadvantages of being small. As gape-limited predators, juvenile snakes are at a particular disadvantage in terms of prey availability, capture, and ingestion. Prey preference often changes with snake size yet previous studies generally compare only one prey type or relative prey size among age classes. Using Western Ribbon Snakes ( Thamnophis proximus (Say in James, 1823)), I investigated the ontogeny of head dimensions and feeding performance on frogs and fish using a range of relative prey sizes. Comparison among snake sizes indicated that smaller individuals had larger relative head sizes than larger conspecifics; however, larger individuals had larger heads. Initial bite position differed between juveniles and adults fed fish but not frogs. Both frogs and fish were generally consumed headfirst by adults and juveniles. Head length did not influence feeding performance in terms of time or pterygoid protractions for snakes fed either fish or frogs. In general, this study suggests that allometry of trophic morphology does not improve feeding performance.