Morphological and physiological indicators of sexual maturity in a viviparous skink, Tiliqua nigrolutea

Life history theory predicts long lived species to be late maturing. In reptiles, the timing of sexual maturity may be determined by either age or by reaching a threshold body size or condition. The blotched blue-tongued lizard, Tiliqua nigrolutea is a long-lived (anecdotally 30+ years) viviparous reptile, in which males reproduce annually and females breed irregularly, usually every 2-3 years in Tasmania. Age at sexual maturity is unknown, as is the timing of onset of the morphological sexual dimorphisms seen in adults (e.g. relatively broader heads in males). We have investigated the timing of the onset of both physiological and morphological sexual maturity in a cohort of juvenile T. nigrolutea and can now report on the age at which seasonal reproductive hormone axis activity, circulating sex hormone levels, sexually dimorphic morphological features (body length, head width:snout-vent length) in juveniles resemble adult proportions. We suggest a pubertal period extending over 1-2 years, particularly in males, and sexual dimorphism in the onset of both morphological and physiological sexual maturity, with males maturing at a younger age and smaller body size than females.