Habitat preference of the eastern fence lizard, Sceloporus undulatus, was investigated in southwestern Virginia. Habitat features were measured at 158 lizard-centered plots and at paired random plots. Landscape-level variables, southerly aspect and mixed forest type, distinguished lizard-centered from random sites. Hatchlings were associated with relatively high temperature at perch height (23 °C), relatively high amounts (per 1- m2) of coarse woody debris (15%) and bare ground (15%), and relatively low amount of litter (34%). Adults and juveniles were associated with a relatively high number of rocks (22 per 0.01 hectare) and amount of coarse woody debris (9% per 1- m2). Habitat preferences were modeled with a Geographic Information System (GIS) using landscape-level variables and with logistic regression and Akaike's Information Criterion using site-level variables. The best-fitting site-level model for adults/juveniles included % CWD. The best-fitting model for hatchlings included % CWD and number of rocks, and the second best-fitting model also included % litter. Landscape (both classes) and site-level models (adult/juveniles only) were tested at 15 GIS-predicted "suitable" study areas and at 15 GIS-predicted "unsuitable" areas. Site-level models for hatchlings were tested with independent data collected at two study areas. Sixteen lizards were found at "suitable" areas and one at an "unsuitable" area; the GIS-based model was a good predictor of lizard presence at the landscape level. The best-fitting site-level models for adults/juveniles and hatchlings were poor predictors of lizard presence while the second best-fitting hatchling model was a good predictor of hatchling presence. / Master of Science

Displays of 36 Sceloporus undulatus hyacinthinus from 8 clutches were recorded on video tape from the day of hatching to adult size during 1978, 1979, and 1980. Nine hundred forty-one displays were analyzed frame by frame, and durations of display units were calculated to the nearest 0.01 s. From the day of hatching, males and females performed both of the display types found in adults, and little significant ontogenic change was found in display patterns or in unit durations; only 7% and 6% of total variance in A and B Displays, respectively, was due to ontogeny. Stereotypy of unit durations both within and among lizards was unchanged across time. Consequently, the display patterns are viewed as being purely innate. Some ontogenic changes were observed in the ways in which the lizards utilized the displays patterns. As compared with hatchlings, older lizards tended to display more frequently, to use display modifiers more often, and to perform displays in aggressive and courtship contexts as well as in assertion. Older females had a significantly higher A: B ratio than males or younger females. These changes in display behavior are viewed as being due to the influences of hormones and social experiences. Slightly more than half of the variance in unit durations for A and B Displays was attributed to inter-individual differences. Of this, approximately half was due to differences among clutches and half to differences among lizards within clutches. For B Displays there were some inter-individual differences (e. g., deleted bobs or dips preceding certain bobs) in the form of the displays as well as in unit durations. Individuals were not consistent in the inclusion of these characteristics in their B Displays. Mean heritability estimates for durations of units 1-12 were 0.60 and 0.38 for A and B Displays, respectively. / M. S.

A study of the lizard Sceloporus undulatus, conducted 1981-82 at an abandoned coal mine in Virginia, was designed to determine whether home range size, home range overlap, and patterns of behavior reflected the requirements of polygyny. The lizards were seen most often on the piles of debris that characterized the study site. Home range size was most strongly influenced by the debris pile size. Mean home range sizes (MCP, N≥5) were 69.3 m² and 59.9 m² for adult males and females, respectively, when data for all debris piles were pooled. The average overlap of home ranges for both study areas and for both years was 32% among adult females and 56% between adult males and females. No overlap among adult males was observed. Adult males usually associated with more than one female. Display frequency (push-ups) and total distance moved during 20 min observation periods were higher for adult males than adult females. Jiggling (rapid head nodding) was observed only in males. The frequencies of other behaviors (e. g. prey capture) did not differ between the sexes. Only one activity, substrate licking by males, seemed to decrease significantly as a function of date. Male home range owners interacted socially with females during the post-reproductive period. This behavior may increase a male's mating success the following spring, as most adult males that appeared on the study site during the mating season in 1982 had been home range owners in 1981. / M.S.

The Fence Lizard (Sceloporus undulatus complex) is a wide ranging North American species complex occurring from the eastern seaboard westward through the great plains and central Rocky Mountains and into the American Southwest. A recent phylogeny suggests four species lineages occur within S. undulatus. Traits within an interbreeding species that are influenced by sexual selection are under different selection pressures and may evolve independently from the selective forces of habitat. Sceloporus lizards have several characters that are influenced by sexual selection. I investigated sexual size dimorphism and allometric relationships of body size (snout vent length), torso length, rear leg length and three measurements of head size in 12 populations from the four species in the S. undulatus complex (N=352) specifically looking for variation among the 4 species. Additionally I investigated the size of signal patches between males and females in three species (N=339 specimens of S. consobrinus, S. cowlesi, S. tristichus) of the S. undulatus complex. Sexual confusion, was recently described in a population of the Sceloporus undulatus complex occurring in White Sands, New Mexico and the behavior is correlated with variation in badge size between male and female lizards. To make inferences about sexual confusion at the species level I investigated the presence and absence of signal patches in female lizards, and compare the sizes of signal patches between males and females. My analyses suggest that torso length and head size are significant sources of sexual size dimorphism but the findings differ from earlier published investigations of sexually dimorphic characters in the species complex. I also find support for the S. undulatus complex being generally a female larger species complex. However two of the 12 populations I investigated displayed male biased sexual size dimorphism. Analysis of signal patches across three species of the S. undulatus complex suggests that sexual dimorphism in signal patch size for S. cowlesi and S. tristichus may not prevent sexual confusion. While the near total absence of signal patches in female S. consobrinus is evidence that sexual confusion is not possible with regards to signal patches.

The phenotypes of hatchling reptiles are influenced by the environmental conditions that embryos experience during incubation, by yolk invested into the egg, and by the genetic contributions of the parents. Phenotypic traits are influenced by these factors in ways that potentially affect the fitness of hatchlings. The physical conditions that embryos experience within the nest affects development, hatching success, and hatchling phenotypes. Thus, the nest site that a female selects can influence the survival of her offspring as well as her overall fitness. In Chapter 1, I addressed this issue through a nest site selection experiment designed to determine the substrate temperature and moisture conditions that female eastern fence lizards (Sceloporus undulatus) select when provided a range of conditions from which to choose. In general, I found that females selected nest sites with conditions that yield high hatching success. In Chapter two, I investigated the relative contributions of incubation moisture conditions, maternal yolk investment, and clutch (genotype) to variation in hatchling phenotypes and survival under field conditions. Eggs from 28 clutches were distributed among two moisture treatments; wet (-150 kPa) and dry (-530 kPa). In another treatment, yolk was removed from eggs to determine the affect of yolk quantity on hatchling phenotypes. After hatching, several phenotypic traits (mass, snout-vent length, tail length, body shape, thermal preference, running speed, desiccation rate, and growth rate) were measured. Hatchlings were subsequently marked and released at a field site in southwest Virginia. Hatchlings were recaptured twice weekly prior to winter and the following spring to monitor growth and survival. I found that incubation moisture and yolk removal affected only hatchling body size; individuals from the dry and yolk removed treatments were smaller in body size than those from the wet treatment. However, clutch was the most important source of phenotypic variation; all phenotypes were affected by clutch. Significant clutch effects suggested the possibility that phenotypic variation had at least some genetic basis. In the field, survival was not affected by incubation moisture and yolk removal, and overall survival was not associated with hatchling body size. Survivors and nonsurvivors differed only in growth rate in the field and running speed measured in the laboratory. Survivors ran faster and grew more slowly than nonsurvivors. To examine the association of clutch with survival, I used clutch mean values to look at the relationship between phenotype and survival. Clutches that produced relatively slow growing individuals and fast runners had higher survival rates than clutches that produced relatively rapid growing individuals and slow runners. In order to grow rapidly, an individual must eat more than slowly growing individuals. Thus, rapid growth rate may increase risk of predation through its association with foraging activity. Individuals that run fast should be capable of capturing prey and evading predators more effectively than individuals that run slowly. Overall, these results emphasize the importance of clutch to variation in phenotypes and survival in hatchling Sceloporus undulatus. / Master of Science