Longevity and sexual size dimorphism of the Pampa de Achala copper lizard Pristidactylus achalensis (Gallardo, 1964)

Abstract

Longevity and sex-specific growth of the neotropical lizard Pristidactylus achalensis was studied from 1993 to 1998 in a population inhabiting the Pampa de Achala. Sierras Grandes de Cordoba, Argentina, at an elevation of 2,000 m. Capture effort concentrated on the territorial adults which were detected while basking. Each of the 149 individuals studied was sexed, morphometrically described and toe-clipped. The second phalanx was used for skeletochronological age estimation and retrospective growth reconstruction, in some voucher specimens additionally the humerus to validate LAG counts in the phalanx cross sections. Longevity was about the same in males (9 LAGs) and females (10 LAGs) but may be even larger in non-territorial individuals. Sexual maturity was usually attained at an age of 3 LAGs, only occasionally one year earlier. With respect to snout-cloaca length, females were always significantly smaller than males of the same age. Bone growth (increase of LAG diameter) revealed that the sexual size dimorphism was related to a significantly lower growth rate of females following hatching. Age and size were correlated (rs = 0.564, n = 149, P ≪ 0.001), but still most of the total size variance remained unexplained by age. Maximum size was approached asymptotically with more than 90% of size increase occuring during the first three years of life: 46.0 ± 1.7 mm (1 LAG), 81.3 ± 5.6 mm (2 LAG), 100.1 ± 0.7 mm (3 LAGs). Territorial individuals rarely were successful to defend a territory more than one activity period, as evidenced by a low recapture probability and a stable between-years age structure of this group.