We surveyed whiptail lizard populations for seven summers (2000–2006) in riparian forests along the Rio Grande in central New Mexico. We captured 5,382 individuals from three parthenogenic species (Aspidoscelis exsanguis, Aspidoscelis neomexicana, and Aspidoscelis uniparens) including 129 hatchlings (young-of-the-year) that were later recaptured as adults. Growth data were fit to a logistic growth model and compared using a likelihood ratio test. Comparisons of growth rates showed that A. exsanguis grew faster than both A. neomexicana and A. uniparens and attained a larger snout–vent length (SVL). Comparisons of capture rates showed that species had similar activity patterns during the summer. Captures of adults peaked in mid-June and decreased in August. Hatchlings became active at the end of July and captures peaked in September. Some individuals were captured several seasons indicating that lizards lived for at least 3–4 yr. Our study shows both similarities and differences in life-history characteristics for three closely related and coexisting whiptail species.