Body size predicts prey preference but not diet breadth in pythons

Abstract

AbstractFor gape‐limited predators like snakes that swallow their prey whole, large‐bodied species with wide gapes should theoretically be able to consume a more diverse range of prey than smaller species with narrow gapes and, therefore, may have broader diets. However, in cases where large‐bodied species exclude small prey, their diets may not necessarily be more taxonomically diverse compared to smaller species. Thus, while body size can potentially predict broad dietary preferences, it cannot always predict diet breadth. We explored the relationship between body size and diet within the Pythonidae—a morphologically diverse clade of dwarf and giant snakes. We gathered ecological data of pythons and tested if python body lengths correlated with diet breadth and diet preferences respectively within a phylogenetic framework. Next, we reconstructed ancestral diets (as proportional use of ectothermic prey in their diets) and body lengths across a phylogeny of 36 species of pythons to explore the evolutionary relationship between these traits. We demonstrate that among extant pythons, body size is not linearly associated with diet breadth but linearly correlates with proportional use of ectothermic (and inversely endothermic) prey. Small‐bodied pythons more often have specialized diets dominated by the use of ectotherm prey whereas large‐bodied pythons tend to have diets dominated by the use of endotherm prey. We further show that the most recent common ancestor of pythons was likely large‐bodied and fed on a diet comprised mostly of endothermic prey. Shifts in diet towards greater proportional use of endothermic prey coincided with increases in body size. Conversely, shifts in diet towards greater proportional use of ectothermic prey coincided with decreases in body size. Our findings contribute to the growing body of work investigating the ecomorphological determinants of snake diets and thus provide further insight into our understanding of these animals' ecology and evolution.