Nesting Habitat and Reproductive Characteristics of the Lizard Cnemidophorus sexlineatus (Lacertilia: Teiidae)

Abstract

Nesting habitat and egg-laying sites of Cnemidophorus sexlineatus were examined for 8 years (1973-1980). Egg clutches (N = 195) were collected from habitats along secondary highways and rural dirt roads in 10 states. Nest construction showed little intraspecific or geographic variation in design or complexity. Nesting sites are characteristically in well-drained, red clay exposures that face S to W. Preferred nesting grounds were near activity burrows. Reproductive characteristics of Cnemidophorus sexlineatus were determined from egg clutches (N = 98) and from autopsied females (N = 90) collected from the Interior Highlands Region in 1973, 1975 and 1980. In 1973 and 1975, females emerged from brumation in early May with regressed ovaries. Follicular enlargement began soon thereafter and occurred sooner in large adult females than in small adults or yearlings. Clutch size (including previously published data) averaged 3.19 (N = 401). A significant positive correlation (r = .69) existed between clutch size (based on counts of oviductal eggs) and snout-vent length. Mean clutch volumes of recently oviposited eggs (< 650 mm3) are not significantly greater in larger clutches (four-egg clutches = ca. 630 mm3) than in smaller ones (two-egg clutches = ca. 600 mm3). Most eggs showed better than a twofold increase in volume during incubation, and two-egg clutches exhibited the greatest range of increase (493.0 to 1376.6 mm3). Two clutches of eggs are commonly produced by adult females, whereas two clutches are infrequent among yearlings. A summer drought in 1980 in the Interior Highlands Region resulted in a dramatic seasonal shift in clutch size. In 1980, two-egg clutches represented 36.5% (27 of 74) of all egg clutches, whereas in a year of higher than average rainfall (1975), two-egg clutches represented 7.4% (2 of 28) of all clutches. The production of significantly smaller clutch sizes (presumably a result of low food resources) agrees with previous studies on the effects of proximal variation in environmental variables on lizard