Notes on Natural History and Behavior of Sceloporus undulatus erythrocheilus in Colorado

A population of the rock-inhabiting lizard, Sceloporus undulatus erythrocheilus was studied from May 1969 to March 1972 on a 3000 m2 study area in the Boulder Mountain Park near Boulder, Boulder Co., Colo. No predation was observed and the only ectoparasite found on the lizard was Geckobiella texana. The population decreased during the study, although the number of resident adults (10-15 per acre) remained about the same. The annual turnover of the resident adult population was about 35% and the maximum age estimation for an individual was 48 months. Lizards in the population were never active from. mid- November through early March. Reproductive activity began after emergence from brumation in late April and continued through mid-June. The testes reached maximum size during the breeding season and regressed to a low point in late July. Recrudescence began by September. Observed females laid one clutch of eggs per year with deposition occurring in late June or early July. Most of the activity of the sedentary females was the result of court- ship, feeding and thermoregulation. The males had a social hierarchy