Intraspecific variability of bite force in Achala copper lizards in a sexual selection context: Who bites harder and when and why?

Abstract

Bite force in lizards is involved in key behaviours such as intrasexual agonistic and intersexual interactions. The relationship between morphology and function is dynamic and sexual pressures can affect bite performance differently between sexes, especially considering the biting position and temporal changes related to the reproductive cycle. The Achala copper lizard (Pristidactylus achalensis) is a highly dimorphic lizard with a short reproductive season. Both sexes present bite scars; however, scar position varies between sexes implying different bite functions. We studied factors influencing bite force such as sex, body size, head morphology and seasonality. We also compared the maximum bite force at two biting positions (frontal and lateral) related to different behaviours (copulation and fighting), and quantified the incidence and scar pattern between sexes. Overall, males bite harder than females and lateral bites were harder than frontal ones. Although bite force did not vary seasonally in males, bite force in females decreased after the reproductive period. Harder bites may confer advantages in mating competition related to the body size in males, while females may benefit from seasonal enhancement of bite force for mate rejection in cases of unwanted copulation.