Growth Rates and Ages at Maturity of Sympatric Scincid Lizards (Ctenotus) in Central Australia

Abstract

Growth rates and ages at maturity of five syntopic species of scincid lizards of the genus Ctenotus were studied in spinifex grasslands near Alice Springs in central Australia. Most species repro- duced only once during the 3-year study (in the second year). There was a diversity of growth rates and ages at maturity in these lizards. The von Bertalanffy growth model described growth of Ctenotus better than did logistic-by-length or logistic-by-mass models; however, the von Bertalanffy model underestimated the growth rates of hatchling Ctenotus. Female Ctenotus grew slower than male Ctenotus but reached larger asymptotic body sizes in most species. Most juvenile C. pantherinus and C. piankai continued to grow during winter and reached sexual maturity by 10 to 11 months of age, but there were year-to-year differences in growth rates of female C. pantherinus. Some juvenile C. cf. helenae and C quattuordecim- lineatus reached the minimum size at maturity by 11 months and could have reproduced in the summer of their first year, but most would not have reproduced until their second spring (22 months). Ctenotus leonhardii was the slowest-growing species and did not reach maturity until at least 18 months of age. Growth rate and age at maturity did not correlate with the absolute body size of the species: the fastest growing species were the largest and smallest species, respectively. The results do not support the pre- dictions of the r-K selection model for species living in variable environments. Predictions of the de- mographic life-history models are more consistent with these results.