Population size, age structure and life expectancy in a Lacerta agilis (Squamata; Lacertidae) population from northwest Italian Alps

Abstract. We studied population size and age structure of the sand lizard Lacerta agilis Linnaeus 1758, from northwest Italian Alps. Twenty-nine (9 males, 15 females, 5 juveniles) and 19 (8 males, 5 females, 6 juveniles) lizards were captured in 2011 and 2012, respectively. Adult population size, estimated by capture-markrecapture, was 54 individuals in 2011 and 39 in 2012. Mean SVL did not significantly differ between males sampled in the two years of the study (mean ± SD, 2011: 67.1 ± 6.6 mm; 2012: 61 ± 8.7 mm). On the contrary, females sampled in 2011 were significantly larger (73 ± 7.2 mm) than females of 2012 (61 ± 7.4 mm). Adult age, assessed by skeletochronology, ranged 2-5 years both in males and females. All juveniles were one-year old. In both years of sampling there was no significant difference in mean age between the sexes. Males were represented mainly by three and four-year old individuals in 2011 and by two-year old individuals in 2012. Females were represented mainly by three -year old individuals in 2011 and by two-year old individuals in 2012. However, age distribution of adults did not differ for each sex as well as between the sexes both in 2011 and 2012. Although our results showed that the examined population of L. agilis has a stable demographic structure, it should be considered seriously vulnerable, because it is relatively isolated from other neighboring populations, has small absolute size and, therefore, may be highly exposed to negative effects of habitat degradation.