Inter‐relationships among body mass, body dimensions, jaw musculature and bite force in reptiles

Abstract

AbstractBite force is important in understanding how feeding biomechanics impacts the life‐history of vertebrates. Bite force has been measured in many lizards and crocodilians but fewer turtles and snakes. Few comparative interspecific studies exist of the inter‐relationships between body size, jaw musculature and bite force. This study collated data reported in the literature for bite force and mass of the jaw musculature in reptiles and explored the relationships between these variables and body mass and size. Two hypotheses were explored: (1) bite force and mass of the jaw musculature scale with body size irrespective of order (as a broad taxonomic grouping) when controlled for phylogeny, and (2) bite force and jaw musculature mass would be directly related and be unrelated to order. Phylogenetically controlled Bayesian analyses showed that in relation to body mass there were different relationships with bite force for testudines compared to saurians and crocodilians. For snout–vent length, squamates and crocodilians exhibited a single relationship, but for head length, all reptile orders exhibited different allometric patterns. Although there was a strong phylogenetic signal in all cases, indicating that there are clusters of closely related species for a measure of size, there was no effect of order on the relationships between measures of body size and mass of the jaw musculature. The relationship between bite force and jaw muscle mass was isometric and did not differ among reptile orders. Several ecological factors may correlate with head morphology and bite force in reptiles. Further studies could explore the evolutionary drivers that shape the relationship between head size, jaw musculature and bite force. Similarities for the relationships between bite force and body size in different reptilian orders suggests that this could be a model system to demonstrate fundamental biomechanical principles of how jaw muscles generate a bite force.