Population structure, growth and reproduction in two species of Tympanocryptis (Agamidae)

Two threatened species of Tympanocryptis (T. lineata and T. osbornei) (the grassland earless dragon clade) are compared for population structure, growth and reproduction from sites around the Australian Capital Territory (ACT) and near Cooma in New South Wales (NSW). Both species showed similar proportions of adults, intermediates and juveniles, as well as similar proportions of adult males and females. Growth patterns had a rapid increase in snout–vent length (SVL) in juveniles. Predicted adult SVL was the same in both species, and females in both species had greater SVL than males. In one year, the appearance of juveniles in the populations was later in T. osbornei than in T. lineata, but that may have been a result of cooler temperatures in the austral summer. Body condition was slightly better in adults of T. osbornei than T. lineata as the former were heavier and shorter. Longevity in the field was similar for both species, being slightly greater than two years, but reproduction may have occurred only once during their lifetime. Colouration associated with reproduction appeared to be the same for both species. Future work can use this information to determine how populations of Tympanocryptis sp. vary in response to environmental changes.