Reproductive ecology of red-chinned lizards (Sceloporus undulatus erythrocheilus) in Southcentral Colorado: comparisons with other populations of a wide-ranging species.

We studied the reproductive ecology of a population of Sceloporus undulatus erythrocheilus near Walsenburg, CO during the summers of 1987-1990. Reproductive activity commences soon after emergence in early May and continues until the middle of July. Females mature in their second year following hatching at an age of 20-21 months and a size of 60-63 mm snout-vent length (SVL). Two clutches, averaging10.9 eggs, are produced per year. Larger females produce larger clutches with an increase of one egg per 3 mm SVL. Average SVL of females was 71 mm. Eggs are reasonably large (0.32 g) and relative clutch mass was the largest reported for the species (34% of body mass). A principal component analysis was used to examine relationships among reproductive characters in 12 populations of Sceloporus undulatus. The analysis suggested that patterns of reproduction in this wide-ranging species result from several factors reflecting both adaptive and phylogenetic sources of variation.