Induction of phenotypic plasticity in rattlesnake trophic morphology by diet manipulation.

Gape-limited predators are restricted in the shape and size of prey items they can ingest by their trophic morphology. Evolutionary theory predicts that gape-limited predators, such as rattlesnakes, should possess plasticity in their trophic morphology to allow them to respond to environmental cues about their prey base. This study examined the effects of two possible influences over trophic morphology in the pit-viper Crotalus viridis viridis. Snakes from six litters were exposed to diet manipulations performed over 480 days. By day 480, snakes from two prey-size treatments exhibited significantly different head shapes. Snakes reared on whole rodents had broader heads, whereas snakes force-fed homogenized prey had narrower heads. Shape differences varied among litters, suggesting that not all litters responded the same to diet manipulations. Results suggest that trophic morphology of rattlesnakes is plastic, at least in some litters, and can be induced by prey items.