The relationship between cranial morphology, bite performance, diet and habitat in a radiation of dwarf chameleon (Bradypodion)

Abstract

Many animals show unique morphological and behavioural adaptations to specific habitats. In particular, variation in cranial morphology is known to influence feeding performance, which in turn influences dietary habits and, ultimately, fitness. Dietary separation is an important means of partitioning ecological niches and avoiding inter- and intraspecific competition. Consequently, differences in dietary resources may help explain phenotypic divergence in closely-related species occupying different habitats, as well as sexual dimorphism. We test this hypothesis on five phenotypic forms of a recent radiation of dwarf chameleons (Bradypodion) that vary extensively in habitat use and cranial morphology. By examining stomach contents, the dietary composition of each phenotypic form is compared to investigate potential differences in feeding strategies. Overall, chameleons in the present study exhibit considerable dietary overlap (at both inter- and intraspecific levels), indicating that diet is not a major driver of variation in cranial morphology within this radiation. However, the stomachs of closed-canopy females were found to contain more prey items than male stomachs, possibly indicating that females require a greater caloric intake than their male counterparts.