The biology of the lizard, Cnemidophorus tesselatus, and effects of pesticides upon the population in the Presidio Basin, Texas

Abstract

During the summer and fall of 1967 and spring, summer and fall of 1968, a study was made of the effects of field applications of pesticides upon the checkered whiptail, Cnemidophorus tesselatus (Say), at Presidio, Texas. The general ecology, reproduction and fat body metabolism of this lizard were studied. In the Presidio area C. tesselatus is generally confined to the farming land within the Presidio Basin. Although pesticides are applied to cotton fields, direct exposure of the lizards to the chemicals is minimized because the time of spraying (early morning) is not coincident with activity. Lizards emerge from hibernation in the study area in April and May. Most adult females show signs of egg development soon after emergence, and lay the first clutch in May or June. A second clutch is laid by late July. No more than two clutches are produced. The number of eggs per clutch ranges from one to eight (average 3.7). Clutch size is related to the size of the female, with more eggs associated with larger lizards. Females of intermediate size are the most numerous adults. Most females reach sexual maturity in 13 to 14 months. Lizards start to hibernate in August and continue to do so until late October. The heaviest applications of pesticides occur in June and July when lizards are active. Lizards emerge from and enter hibernation when pesticide applications are minimal. Lizards probably acquire most of the residues by eating contaminated insects..