Autotomy in Achala copper lizard: do sex and body size traits influence tail loss and regeneration?

Abstract Autotomy in animals, the voluntary loss of a body part at a specific location, is a widespread behaviour observed across various groups. This mechanism provides several advantages, such as predator evasion, escape from entrapments, and even reduced injury costs from agonistic interactions. Lizards display tail autotomy in response to predation and intraspecific aggression. Moreover, it is common for these reptiles to have sexually dimorphic traits, such as colouration and body size, which may influence predation risk and consequently their antipredatory strategies. This study focuses on the Achala copper lizard ( Pristidactylus achalensis ) which inhabits an isolated highland ecosystem in central Argentina. This species is an ideal study model due to its territorial and aggressive behaviour, high intraspecific competition and sexual dichromatism. The aims of this study were to determine the influence of sex and body size on the occurrence of tail autotomy in P. achalensis . Additionally, we assessed the cost of autotomy by analysing the distance between the vent and the tail cut. Furthermore, we investigated the possibility of repeated tail autotomy by a single individual. Our results showed that in P. achalensis , sex and body size interacted significantly resulting in different patterns of tail autotomy. In females, the frequency of autotomy increased gradually with body size, whereas in males it increased more abruptly and reached its maximum frequency at smaller body sizes than in females. Males presented higher autotomy frequencies than females, likely because they are more likely to be perceived by avian predators than cryptic females. The findings of this study contribute to broadening the knowledge of lizard behaviour, shedding light on the complex interplay between predation, intraspecific competition and reproductive dynamics in this unique species.