Skeletochronology uncovers population-and sex-dependent growth trajectories in the sand lizards of Western Poland

Obtaining population demography metrics in a non-lethal way is essential for the evidence-based management of reptiles that are declining in increasingly degraded European landscapes. Here, we quantified life-history traits of the sand lizard Lacerta agilis argus in Western Poland and tested whether they varied by sex and locality. Using skeletochronology, we aged 177 individuals from three populations inhabiting different habitats. The lizards reached sexual maturity after their second hibernation; and the mean adult age was 4.6 ± 1.9 years (range 2-8). The annual survival rate was 0.80 and the adult life expectancy was 5.25 years. The Sexual Dimorphism Index (SDI) was female-biased but small (SDI = 0.04). Linear modelling showed that the snout-vent length increased with age, yet the age-size slope differed between sexes and among populations: females and lizards from the two warmer, drier sites grew faster and attained a larger body size than males or lizards from the cooler forest site. Sex had no main effect on the size once age was accounted for. These results demonstrate that even over short geographic distances, habitat thermal conditions modulate the growth trajectories in this ecologically flexible species. Our study high-lights the value of skeletochronology for rapid, non-lethal assessments of the population demography in temperate lizards.