Sexual Dimorphism in Head Shape and Bite Force in the Northern Alligator Lizard, Elgaria coerulea

Bite force capacity is a directly related performance correlate of head shape and is an integrative measure of performance in capturing and handling prey, fighting, and mating, especially for males. We investigated head shape and bite force dimorphisms in a small semifossorial lizard (Elgaria coerulea) that exhibits females-larger sexual size dimorphism (FL-SSD) in some populations but not in others. Specifically, we explored how body size, head shape, and bite force compare between the sexes relative to any dimorphisms in body or head size in a coastal population of E. coerulea. Female larger-SSD was confirmed for this population, but it contrasted with males-larger sexual dimorphism in head size (ML-SDHS). Males also had greater bite force than females of similar size. The secretive habit of E. coerulea hampers observations of behavioral interactions among conspecifics. However, it is expected that lizards with FL-SSD will have ML-SDHS if males with greater bite force win fights with other males over access to mates and/or if greater bite force increases copulation success.