Phenotypic Plasticity of Rattlesnake Trophic Morphology

The trophic morphology of gape-limited predators constrains the shape and size of prey items they can ingest. Trophic morphology consists of any morphological feature that is involved in the handling and ingestion of food. Diet has a profound effect on the morphology of many gape-limited predators. Identifying how prey type and resource level affect the morphology of different populations is an essential step in understanding the mechanisms contributing to patterns of morphological diversity. Species interactions (Chapter 1) induce plasticity in morphology that can lead to increased fitness, morphological divergence, and eventually speciation. In Chapter 2, a laboratory study tested the effects of defensive strikes on snake trophic morphology. In conjunction with morphological measurements, the metabolic costs of replacing venom were quantified. Control and milked snakes had baseline metabolic rate and morphology quantified before treatment manipulation. Milked snakes showed no significant difference in metabolic rate after expending venom than. Trophic morphology was not significantly different after snakes struck defensively. Venom expenditure does not impose significant increases to metabolic rate or changes in trophic morphology. In Chapter 3, I quantified the effects of starvation on trophic morphology and its allometric relationship with body size. Starvation periods of short (100 days) and long (200 days) intervals were compared to control snakes. Shorter periods of starvation had no effect on morphology or its relationship with body size, but longer periods resulted in a significant shift in the relationship between head and body size. Results showed extended periods of starvation can significantly alter the allometry of trophic morphology in snakes