^3 



days after oviposition. Nest sites were selected in substrate permit- 

 ting easy burrowing, frequently on a well-drained slope with sufficient 

 soil moisture to insure successful incubation. These slopes were typi- 

 cally devoid of vegetation and exposed to unrestricted solar radiation 

 at all times of the day. Gravid females intent on nesting behave quite 

 differently from non-nesting individuals and these behavioral differen- 

 ces are readily distinguishable. This behavior is best characterized 

 by extended movements out of the home range, scouting of unfamiliar 

 terrain, intensive chemoreception and extreme wariness. Observations 

 indicate that females compete for and "parasitize" the nest sites of 

 one another. Nest sites are defended prior to and immediately after 

 oviposition. Nest sites are communal and females will return periodi- 

 cally over 3 days to scratch additional debris about the nest. It is 

 suggested that lizards return to nest in the same area from which they 

 hatched. Burrows and burrowing behavior is described. Reproductive 

 success was significantly higher in 1965 than 196^^. Incubation time 

 varies from 60 to 7^ days; the most important variable the length of 

 retention of oviducal eggs. It is suggested that older females retain 

 eggs longer because they are more adept at selection and preparation of 

 nest sites, implying ontogenetic learning. Nest temperatures fluctuat- 

 ed daily between 20-34°C. The first hatchlings in 1965 appeared during 

 the second week of September, although normally they appear two weeks 

 earlier. They remain adjacent to the nest and use it for an overnight 

 shelter after hatching. Many may use it as a hibernaculum as many are 

 caught in the same spot the next spring. Hatchlings continued to emer- 

 ge until October 5, leading to different size classes which are main- 

 tained throughout adulthood. Reproductive maturity is reached during 

 their 3rd growing season (approximately 22 months). Growth rates de- 

 cline sharply when subadult size is reached; rates are intimately asso- 

 ciated with annual environmental productivity. Hatchlings vary between 

 39.1 mm and ^S.2 mm SVL and 1.^ gm to 2.9 gm. Body temperatures be- 

 tween 3^-'f2.6°C. (mean 39.3°C.) were recorded for active lizards. 

 Spring emergence occurs from mid- to late April when soil temperatures 

 to which lizards are exposed reach at least 15°C., fat reserves become 

 depleted and the hunger drive activated. Adults disappear by mid-Aug- 

 ust although activity continues through mid-October. Hibernacula are 

 all located on SE-facing slopes completely devoid of vegetation and ex- 

 posed to full solar radiation. The smallest lizards are the first and 

 the largest last to appear in the spring. Daily activity usually be- 

 gins between 8 and 10 a.m.; the greatest amount of activity occurs be- 

 tween 10 a.m. and 1 p.m. Subtle shifts in this pattern occur during 

 the active season. 



Daily recapture rates average 15-20% of the resident population; 

 a maximum of 34% was recorded on August 2nd. All members of the popu- 

 lation are not active each day, even though optimum conditions may pre- 

 vail. Failure to emerge is attributed primarily to success in obtain- 

 ing food. Different kinds of burrows are dug and utilized for differ- 

 ent purposes; an individual lizard may dig several and use them all 

 over the course of a season. All burrows are exclusive and vigorously 

 defended against intrusion by non-residents. Other types of social in- 

 teraction do not. occur. Home ranges are maintained, but are not mutu- 

 ally exclusive and overlap broadly. Sizes for three were .16, .21 and 



