The thermoregulation of lizards depends highly on the environment they inhabit. Thermoregulation is crucial for physiological processes and affects therefore the life history of the lizard. High altitudes are characterized by a colder climate than on lower altitudes, and these environmental factors affects the thermoregulation of lizards. Lizards can however adapt to colder climates by adjusting their physiology and/or behavior. In this study two populations of Liolaemus aparicioi, an endemic lizard inhabiting the valleys close to La Paz, were observed at two different altitudes to investigate any differences in behavior or habitat use that could compensate for the high altitude. The behavioral displays associated to thermoregulation and the use of habitat were recorded in order to assess how they allocated their time and how they used the habitat available. The mean values of most parameters measured indicated that the population on the high altitude do compensate for the high altitude by behavior and habitat use.

Faculty of Science School of Animal ,Plant and Enviromental Sciences 9707660j McConnachie@ukzn.ac.za / Characteristics comprising an energy budget of Pseudocordylus melanotus melanotus were investigated in terms of limiting factors for the lizard’s distribution, and included measures of thermal biology, metabolism and digestive physiology. Pseudocordylus m. melanotus is rupicolous, is limited to the temperate parts of southern Africa and exhibits adaptations to these environments. The distribution of the lizard was modelled using two different climate envelope modelling techniques, which are discussed in terms of the energy budget and factors limiting the distribution of the lizard. Pseudocordylus m. melanotus exhibits wide thermal tolerances. It can withstand body temperatures (Tb) below freezing, but freezing of body water, which occurs at ca. -5 ºC, is lethal. The lower critical minimum temperature was a surprisingly high measure for an apparently cold-adapted lizard. In the laboratory, the selected body temperature (Tsel) was ca. 30 ºC. In the wild, lizards thermoregulate by shuttling between hot and cold microclimates, modifying body postures and regulating activity times, and select Tbs of ca. 29 ºC in summer and ca. 26 ºC in winter. Energy expenditure was measured over a range of temperatures. MR increases significantly with increasing temperature. Body mass and metabolic rate (MR) were significantly related at 30 ºC only. The lack of significance at other temperatures can be ascribed to the small range of body mass over which measures were made. Energy gain in P. m. melanotus was quantified in terms of prey capture rates and by measuring aspects of digestive physiology. Prey capture attempts were 35 % successful and occurred ca. every 2 h 30 min in the field. Lizards consumed a variety of arthropods, but mainly ate beetles. Digestive rate and appetite increased significantly with increasing temperature. Apparent digestive efficiency (ca. 94 %) and apparent assimilation efficiency (ca. 87.2 %) were not affected by temperature. iii Two energy budgets were calculated; one based mainly on laboratory measures and the other based on the thermal profile of lizard body temperature measured in the field. The laboratory energy budget was approximately half that of the field energy budget. The field energy budget, however, provided a more realistic view of energy expenditure since it covered almost the entire thermal range experienced by lizards. Between 592.53 kJ (field energy budget) and 940.06 kJ (laboratory energy budget) per year is required for a standard 30 g P. m. melanotus to remain in energy balance. This means that lizards need to consume between 73.55 and 116.69 g of mealworms per year, which equates to ca. 740 to 1200 average mealworms. Any energy gained over and above these requirements can be allocated to growth, reproduction and storage. In terms of the lizard’s distribution, it will be excluded from areas where the available thermal environment and prey abundance do not allow the lizard to maintain a positive energy balance. The lizard is apparently at the cold limit of its range, so predicted climate change in southern Africa is unlikely to have a significant effect on the distribution of the lizard. Suitable crevices are essential to the lizard’s survival, particularly during periods of extreme cold when lizards may experience Tbs where they are incapacitated, or effectively ‘comatose’, while in retreats.

Thermal ecology and movement of the Leopard Lizard, G. wistizeniwere studied at Frog Spring, adjacent to the Alvord Desert, and at various locations throughout the Alvord Basin. Seasonal activity is known to occur from early May to mid-October, but abundance. gradually decreases after late July. During favorable late spring, and summer weather lizards exhibit a bimodal pattern of diel activity with some activity occurring at all hours of the day between 0600 and 1800 H. At other times activity was unimodal. Emergence was apparently largely temperature dependent and did not occur until sand temperature approximated 21°C. Retreat appeared to be temperature independent, and was initiated by exogenous or endogenous stimuli at sand temperatures often above body temperatures acceptable for normal activity. For the period of study, juveniles exhibited diel activity patterns similar to adults, and were found during all hours in which adults were encountered. Body temperatures of field active lizards, largely affected by the immediate weather conditions, , ranged from 18.6° to 43.4°C. Because of a variety of thermoregulatory response (changes in location, posture, and orientation, color change, burrowing, shade-seeking, and panting), even during unfavorable weather conditions, most body temperatures fell within a narrower range. Nonetheless, the ability of field active lizards to precisely thermoregulate was limited, and the levels of body temperature maintained usually encompassed a broader range than those maintained in a thermal gradient. The mean body temperature of field active lizards during favorable weather conditions, and that of active lizards in a thermal gradient, did not differ significantly, and seemed to indicate a narrow range of body temperature preference. However, prevailing weather conditions were frequently unfavorable, thus limiting the extent of time during which selection of preferred body temperature could occur. Consequently, though activity depended on the attainment of certain temperature levels, G. wislizeni was forced to adapt to a broader range of body temperatures when performing most routine tasks. The necessity of precision thermoregulation is unclear, but apparently physiological efficiency was not greatly diminished over the broad range of body temperatures fiefd active lizards were often accepting. Relatively speaking, movement in G. wislizeni was extensive. Adult males occupied an average area more than twice the size of adult females and juveniles. Plotted polygons, constructed from sighting points, tended to be elongate. The extent to which lizards occupied a definite home range was uncertain. Adult males , continuously expanding the area occupied, probably lacked a home range. Adult females, demonstrating . little area expansion, perhaps maintained a home range. Territoriality by means of intraspecific display or aggression appeared negligible in G. wislizeni.Adult males did not demonstrate such behavior toward one another . Based on a limited extent of area overlap, adult females may have exhibited territoriality toward members of their sex. Movement per hour revealed results similar to area occupied, with adult males traveling an average distance of nearly three times as great as adult females and juveniles. Greatest distances frequently coincided with peak diel activity. Individual moves were frequent in adult males and juveniles, but infrequent in ~ adult females. Adult female long moves were similar in distance to adult males, but exogenous stimuli perhaps linked with home range maintenance restricted the frequency of such jaunts. Movement in G. wislizeni appeared independent of environmental thermal conditions when body temperature was within the range acceptable for normal activity. Diel movement appeared to be random in the species. Seasonal movement in juveniles, based on dispersion data, appeared directional.

Abstract There are a remarkable variety of sex determination systems among different animal taxa. In most animals, sex is determined chromosomally. Although in an increasing number of animals sex determination has been found to be influenced primarily by the environment. Species with genotypic sex determination (GSD) have their sex determined at the time of fertilization, by genetic factors alone and those with environmental sex determination (ESD) have their sex determined by environmental factors that act after fertilization. Temperature-dependent Sex Determination (TSD), whereby the sex of the developing embryos depends on the temperature at which they develop is widespread in oviparous reptiles and occurs in all crocodilians, marine turtles and tuatara examined to date and is common in many freshwater turtles and lizards. SECTION ONE Temperature-dependent sex determination (TSD) was never expected to occur in viviparous reptiles, as thermoregulation by pregnant females would result in relatively stable gestation temperatures. Temperature-dependent sex determination and viviparity goes against all the basic assumptions that TSD occurs in oviparous reptiles where temperatures within a nest vary widely. However, skewed sex ratios as a result of incubation temperature indicated the possibility of TSD in the viviparous lizard Eulamprus tympanum. In my first experiments I show the first recorded case of a viviparous reptile with TSD. The developing embryos of the viviparous skink E. tympanum are subject to TSD, with gestation temperature having a highly significant effect on sex and warmer temperatures giving rise to male offspring (Chapter 1). Sex is fully determined at the time of birth and can be differentiated histologically into testes or ovaries (Chapter 2). The morphology and histological characteristics of the gonads of neonatal E. tympanum resulting from the treatment temperatures described in chapter 1 illustrate that sex in E. tympanum is easily distinguished at the time of birth and corresponds with the presence or absence of hemipenes. Males are histologically characterised by an elongated gonad consisting of seminiferous tubules with either no cortical epithelium or, if present at all, in a very thin band. If they are present, M�llerian ducts, showing signs of degeneration, are attached to the kidney by a shortened mesosalpinx. Females are histologically characterised by an irregularly shaped gonad consisting of a thick cortical epithelium that occasionally contains oocytes. The M�llerian ducts are obvious structures attached to the kidney by a fibrous mesosalpinx. The presence or absence of hemipenes is a reliable technique for determining sex in newborn E. tympanum. Sex determination is easiest to perform on neonates within the first few days of birth as hemipenes become increasingly difficult to evert as neonates age, however, with practice they are easily identified without full eversion. SECTION TWO The thermal biology of E. tympanum in the field is restricted by both the thermal properties of their habitat (Chapter 3) and behavioural modifications when faced with a predation threat (Chapter 4). The available temperatures in the field suggest that TSD is biologically relevant in the species and not just a laboratory artefact; E. tympanum can attain mean selected temperatures achieved in the laboratory but the proportion of time at the temperature is restricted. Females actively thermoregulate in the field, although they are restricted in their efficiency of thermoregulation by environmental constraints, for example, microhabitat structure, weather conditions, predator avoidance and social ranking. The highly territorial nature and high densities of E. tympanum present in Kanangra Boyd National Park potentially force less dominant individuals into less favourable habitats that are significantly cooler. An important point is that gravid females in more favourable habitats in the period encompassing the middle third of development (the assumed sex determining period) are selecting higher temperatures, with lower variance and have greater thermoregulatory efficiency than during the rest of pregnancy, therefore, thermoregulating more precisely during this thermosensitive period (Chapter 3). Chemosensory cues provide important information on the risk of predation. Hence, chemoreception is a common mechanism used by many species to detect the presence of, and subsequently respond to, a potential predator. The perceived risk of predation may force retreat to sub-optimal conditions, forcing a trade-off between the risk of predation and the ability to acquire resources. The basking regime maintained by gravid female E. tympanum, can directly alter sex ratios of offspring produced through temperature-dependent sex determination (Chapter 1). The avoidance of predator scents may restrict basking ability and in turn alter the sex of offspring produced. I measured responsiveness to chemical cues using tongue flicks as an indicator of chemical discrimination in females of different reproductive condition. I then measured activity and basking behaviour of gravid and non-gravid females in experimental enclosures in the presence of various chemical stimuli to determine if basking opportunity is compromised by the presence of a predator scent. Females respond differently depending upon reproductive condition, with gravid females responding most significantly to a predator scent. Activity, basking frequency, and time spent in the open (basking duration) are significantly reduced in gravid females in the presence of a predator stimulus. Under laboratory conditions, gravid females modify their behaviour and forego the opportunity to bask when there is a perceived predation risk (Chapter 4). SECTION THREE As female viviparous reptiles can regulate the temperature of the embryo by maternal temperature selection (Chapter 1), the occurrence of TSD in E. tympanum opens the possibility for females to select the sex of offspring. Reproducing females may benefit by facultatively adjusting their investment into sons over daughters or vice versa, in response to population wide shifts in adult sex ratios. Female E. tympanum, can manipulate the sex of their offspring in response to sex imbalances in the population using temperature-dependent sex determination (Chapter 5). When adult males are scarce, females produce male-biased litters and when adult males are common, females produce female-biased litters. The cues used by a female to assess the adult population are not known, but presumably depends upon the female�s experience throughout the breeding season and is the subject of further investigation (Chapter 6). The maternal manipulation of offspring sex ratio in E. tympanum suggests a selective advantage of temperature-dependent sex determination. Any facultative sex ratio response needs to recognise the scarcity of one sex in order to overproduce that sex in the next generation; offspring sex ratio will vary inversely with adult sex ratio. Maternal sex allocation in E. tympanum is linked with population (or adult) sex ratio (Chapter 5), and one of the mechanisms by which females recognise an imbalance may be linked to visual recognition of males (Chapter 6). Females maintained throughout pregnancy without any male stimulus produce entirely male offspring (Chapter 5). In contrast females exposed to male stimulus produce both sexes (Chapter 5). Females respond differently to varying degrees of male stimulus and visual recognition of males in a population may be more important than chemoreception. In the absence of visual cues, females produce more male offspring, even when chemosensory cues are present (Chapter 6). The study system presented here offers many advantages over oviparous species with TSD, due to E. tympanum being relatively short lived and fast maturing. Thus, the fitness consequences over multiple generations as a result of gestation can be investigated. Viviparity allows maternal control of embryonic temperature during gestation and a means of maternal sex allocation. Until now the maternal side of TSD and sex allocation has been where the mother deposits her eggs and the allocation of sex steroid hormones at oviposition, both of which have been difficult to study. The work presented and the study system itself should inspire great interest in TSD and viviparous reptiles.

Abstract There are a remarkable variety of sex determination systems among different animal taxa. In most animals, sex is determined chromosomally. Although in an increasing number of animals sex determination has been found to be influenced primarily by the environment. Species with genotypic sex determination (GSD) have their sex determined at the time of fertilization, by genetic factors alone and those with environmental sex determination (ESD) have their sex determined by environmental factors that act after fertilization. Temperature-dependent Sex Determination (TSD), whereby the sex of the developing embryos depends on the temperature at which they develop is widespread in oviparous reptiles and occurs in all crocodilians, marine turtles and tuatara examined to date and is common in many freshwater turtles and lizards. SECTION ONE Temperature-dependent sex determination (TSD) was never expected to occur in viviparous reptiles, as thermoregulation by pregnant females would result in relatively stable gestation temperatures. Temperature-dependent sex determination and viviparity goes against all the basic assumptions that TSD occurs in oviparous reptiles where temperatures within a nest vary widely. However, skewed sex ratios as a result of incubation temperature indicated the possibility of TSD in the viviparous lizard Eulamprus tympanum. In my first experiments I show the first recorded case of a viviparous reptile with TSD. The developing embryos of the viviparous skink E. tympanum are subject to TSD, with gestation temperature having a highly significant effect on sex and warmer temperatures giving rise to male offspring (Chapter 1). Sex is fully determined at the time of birth and can be differentiated histologically into testes or ovaries (Chapter 2). The morphology and histological characteristics of the gonads of neonatal E. tympanum resulting from the treatment temperatures described in chapter 1 illustrate that sex in E. tympanum is easily distinguished at the time of birth and corresponds with the presence or absence of hemipenes. Males are histologically characterised by an elongated gonad consisting of seminiferous tubules with either no cortical epithelium or, if present at all, in a very thin band. If they are present, M�llerian ducts, showing signs of degeneration, are attached to the kidney by a shortened mesosalpinx. Females are histologically characterised by an irregularly shaped gonad consisting of a thick cortical epithelium that occasionally contains oocytes. The M�llerian ducts are obvious structures attached to the kidney by a fibrous mesosalpinx. The presence or absence of hemipenes is a reliable technique for determining sex in newborn E. tympanum. Sex determination is easiest to perform on neonates within the first few days of birth as hemipenes become increasingly difficult to evert as neonates age, however, with practice they are easily identified without full eversion. SECTION TWO The thermal biology of E. tympanum in the field is restricted by both the thermal properties of their habitat (Chapter 3) and behavioural modifications when faced with a predation threat (Chapter 4). The available temperatures in the field suggest that TSD is biologically relevant in the species and not just a laboratory artefact; E. tympanum can attain mean selected temperatures achieved in the laboratory but the proportion of time at the temperature is restricted. Females actively thermoregulate in the field, although they are restricted in their efficiency of thermoregulation by environmental constraints, for example, microhabitat structure, weather conditions, predator avoidance and social ranking. The highly territorial nature and high densities of E. tympanum present in Kanangra Boyd National Park potentially force less dominant individuals into less favourable habitats that are significantly cooler. An important point is that gravid females in more favourable habitats in the period encompassing the middle third of development (the assumed sex determining period) are selecting higher temperatures, with lower variance and have greater thermoregulatory efficiency than during the rest of pregnancy, therefore, thermoregulating more precisely during this thermosensitive period (Chapter 3). Chemosensory cues provide important information on the risk of predation. Hence, chemoreception is a common mechanism used by many species to detect the presence of, and subsequently respond to, a potential predator. The perceived risk of predation may force retreat to sub-optimal conditions, forcing a trade-off between the risk of predation and the ability to acquire resources. The basking regime maintained by gravid female E. tympanum, can directly alter sex ratios of offspring produced through temperature-dependent sex determination (Chapter 1). The avoidance of predator scents may restrict basking ability and in turn alter the sex of offspring produced. I measured responsiveness to chemical cues using tongue flicks as an indicator of chemical discrimination in females of different reproductive condition. I then measured activity and basking behaviour of gravid and non-gravid females in experimental enclosures in the presence of various chemical stimuli to determine if basking opportunity is compromised by the presence of a predator scent. Females respond differently depending upon reproductive condition, with gravid females responding most significantly to a predator scent. Activity, basking frequency, and time spent in the open (basking duration) are significantly reduced in gravid females in the presence of a predator stimulus. Under laboratory conditions, gravid females modify their behaviour and forego the opportunity to bask when there is a perceived predation risk (Chapter 4). SECTION THREE As female viviparous reptiles can regulate the temperature of the embryo by maternal temperature selection (Chapter 1), the occurrence of TSD in E. tympanum opens the possibility for females to select the sex of offspring. Reproducing females may benefit by facultatively adjusting their investment into sons over daughters or vice versa, in response to population wide shifts in adult sex ratios. Female E. tympanum, can manipulate the sex of their offspring in response to sex imbalances in the population using temperature-dependent sex determination (Chapter 5). When adult males are scarce, females produce male-biased litters and when adult males are common, females produce female-biased litters. The cues used by a female to assess the adult population are not known, but presumably depends upon the female�s experience throughout the breeding season and is the subject of further investigation (Chapter 6). The maternal manipulation of offspring sex ratio in E. tympanum suggests a selective advantage of temperature-dependent sex determination. Any facultative sex ratio response needs to recognise the scarcity of one sex in order to overproduce that sex in the next generation; offspring sex ratio will vary inversely with adult sex ratio. Maternal sex allocation in E. tympanum is linked with population (or adult) sex ratio (Chapter 5), and one of the mechanisms by which females recognise an imbalance may be linked to visual recognition of males (Chapter 6). Females maintained throughout pregnancy without any male stimulus produce entirely male offspring (Chapter 5). In contrast females exposed to male stimulus produce both sexes (Chapter 5). Females respond differently to varying degrees of male stimulus and visual recognition of males in a population may be more important than chemoreception. In the absence of visual cues, females produce more male offspring, even when chemosensory cues are present (Chapter 6). The study system presented here offers many advantages over oviparous species with TSD, due to E. tympanum being relatively short lived and fast maturing. Thus, the fitness consequences over multiple generations as a result of gestation can be investigated. Viviparity allows maternal control of embryonic temperature during gestation and a means of maternal sex allocation. Until now the maternal side of TSD and sex allocation has been where the mother deposits her eggs and the allocation of sex steroid hormones at oviposition, both of which have been difficult to study. The work presented and the study system itself should inspire great interest in TSD and viviparous reptiles.

I studied translocation of Texas horned lizards on Tinker Air Force Base, Midwest City, Oklahoma, using correlative and mechanistic habitat suitability models. My goals were broadly classified into two categories: first, to determine if the addition of mechanistic data layers (i.e., habitat-niche models) in a correlative model improved the overall accuracy of model predictions, and second, to apply the best model produced from my dataset to a planned translocation event on Tinker Air Force Base. Correlative data layers (i.e., habitat models) included typically applied datasets such as vegetative components, Euclidean distance statistics, neighborhood analyses, and topographically-derived information. Mechanistic data layers were estimates of thermal suitability derived from field-collected datasets and biophysical calculations, and estimates of prey availability taken from interpolated datasets. I estimated habitat suitability using the partitioned Mahalanobis distance statistic, which is a suitable model technique for presence-only data. Translocated and resident lizards were monitored via radiotelemetry and using fluorescent powder trails. Telemetry locations and powder trails were overlaid onto habitat suitability models to provide the datasets used to quantify interaction between site occupancy and habitat model predictions. Lizard paths were tested against random walk models to determine efficiency of travel, and site occupancy metrics (powder track and telemetry Mahalanobis distance values) were tested using parametric (repeated-measures ANOVA) and nonparametric (Wilcoxon rank-sum and signed-rank tests) tests. Mechanistic data layers did not substantially improve model accuracy over correlative-only layers, and data layers taken from mixed bare soil-vegetation, shrub, and grassland habitat types dominated important eigenvector weights. Analyses of fluorescent powder track data suggested that lizards did not move through habitat differently from a random walk model, potentially due to neighborhood factor loadings strongly influencing the area in which entire trails traveled. Wilcoxon tests and repeated-measures ANOVA results suggested that although lizards experienced different median Mahalanobis distance values by group (translocated, resident), there appeared to be an overall decrease in distance scores for translocated individuals over time. In this context, translocated individuals seemed to acclimate their behavior to areas that were predicted to be more suitable by Mahalanobis classifiers. Although survival results were not encouraging and habitat models did not suggest that my translocation site was ideal, my data supports the idea that translocations may be aided in the future by modeling efforts. My models suggest that mechanistic data layers may not improve classification accuracy over correlative processes, but this may be due to inaccurate representation of specific mechanisms over spatial and temporal scales. Future work should focus on including more explicit measures of mechanisms, as well as broadening biotic influences on species distributions (i.e., predator distribution, intra- and interspecific competition).

Disturbance due to habitat restoration and urbanization can threaten populations of sensitive wildlife species. I examined 2 aspects of the ecology of Texas horned lizards (Phrynosoma cornutum), a Species of Special Concern in Oklahoma. I studied the effects of native prairie restoration and urban development on a population of P. cornutum on an urban wildlife reserve at Tinker Air Force Base, Oklahoma. I also studied population vital rate variation in 2 populations of P. cornutum using deterministic elasticity and life-stage simulation analyses. My research on the effects of habitat disturbance on urban P. cornutum focused on Wildlife Reserve 3 (WR3) at Tinker Air Force Base, which has a population of P. cornutum that has persisted for many years. I quantified daily movement rates, home-range size, changes in spatial distribution, survival rates, and population size and density over 9 years (2003-2011). Movement rates of P. cornutum were affected by a 3-way interaction of sex, period (reproductive vs. non-reproductive), and study stage (2004-2005, 2007-2008, and 2009-2011). Stages represented variation in the type and level of anthropogenic disturbance on the site. Home-range size did not vary by sex, but was smaller during the non-reproductive period than the reproductive period. Spatial analyses indicated that disturbances due to restoration activities had little effect on the spatial distribution of P. cornutum on WR3. Survival was affected by season (inactive-season survival was higher), stage (declining survival in later stages with more disturbance), an interaction of season and stage, and disturbance (covariate of proportion of an individual's home range in disturbed areas for a given year; small negative effect), with little evidence for variation in survival by sex. Major causes of mortality included depredation and anthropogenic causes. I estimated a population size of 32.9 ± 4.7 (95% CI of 28.1-49.0) individuals (excluding hatchlings) with a corresponding density of 2.68 lizards/ha. Spatial analyses did not support the hypothesis that disturbance associated with restoration activities affected the spatial ecology of P. cornutum on WR3. However, these results were not entirely conclusive, due to the logistical constraints of working on a single site with an uncommon species. Size and density of the P. cornutum population has apparently declined since 2005. This decline is likely a consequence of 2 factors: the 2008 translocation of 17 adult lizards from an area adjacent to WR3 impacted by housing development coupled with a decrease in the annual survival rate of adults over time. I compared the vital rates of the population of P. cornutum on WR3 to a site in south Texas, the Chaparral Wildlife Management Area (CWMA). The Chaparral WMA population had lower adult survival and higher fecundity than WR3. I predicted a trade-off between the effect of adult survival and fecundity on population growth rate (&lambda). I found that recruitment in P. cornutum most affected &lambda at both sites. Stochastic life-stage simulation analysis indicated that hatchling survival most affected &lambda in both populations. There was a trade-off in effect on &lambda between juvenile survival and fecundity between the two sites; fecundity affected &lambda more at the CWMA. Adult survival had minimal effects on &lambda in both populations. My study suggests that managers can address P. cornutum declines in similar ways across the species' range.

Niveoscincus ocellatus is an important species in historical analyses of the evolution of viviparity because it is the species upon which the type II chorioallantoic placenta was based. Here we describe the net nutrient uptake across the placenta of N. ocellatus for comparison with other species of skinks with complex placentae. N. ocellatus is highly placentotrophic, with neonates being 1.68-times larger in dry matter than the fresh eggs. There is an increase of nitrogen from 6.3 ± 0.2 mg to 9.2 ± 0.6 mg, and ash from 3.8 ± 0.3 mg to 6.7 ± 0.6 mg. The increase in ash is made up by a more than two-fold increase in the amounts of calcium, potassium and sodium. There is no significant difference in lipids in the neonates compared to fresh eggs, so considerable lipid must have crossed the placenta to provide energy for embryonic development. N. ocellatus is significantly more placentotrophic than Niveoscincus metallicus, which also has a complex chorioallantoic placenta. Discovery of substantial placentotrophy in this genus confirms that two lineages of Australian lygosomine skinks (represented by the genera Pseudemoia and Niveoscincus) have evolved this pattern of embryonic nutrition and supports the hypothesis that the evolution of reptilian placentotrophy involves specialisations in addition to structural modifications of the chorioallantoic placenta.

Faculty of Science School of Animal,Plant and Enviromental Studies 0204322k thibbitts@tamu.edu / I investigated three mechanisms (endurance rivalry, contest competition, and mate choice) of sexual selection and the influence of multiple signals on intrasexual and intersexual encounters in the common barking gecko (Ptenopus garrulus). Aspects of the ecology of barking geckos were also studied to facilitate the investigation of sexual selection. Barking geckos exhibited sexual size dimorphism in relation to head size, with males having wider heads. No differences in diet or size of prey ingested were observed between the sexes, indicating that niche divergence was not occurring. Therefore, the difference in head width was best explained by sexual selection (male contest competition). Barking gecko diet was dominated by termites by number and volume. The peak reproductive season was in October for both sexes. I used activity patterns to determine if males emerged before females from winter dormancy, a key assumption of the protandry-based mating system model. Activity patterns were significantly different between males and females. Males were active in higher numbers early in the breeding season. Male and female activity patterns along with evidence that male territories were established before female emergence, testicular recrudescence likely coincides with male emergence, and larger males have larger territories and better reproductive success, suggest that barking geckos have a protandry-based polygynous mating system. I also tested for clustering of geckos on the landscape to determine if barking geckos lek. Clustering was found to occur in some instances, but barking geckos did not iii meet the criteria for a ‘classical’ lek species because males use calling sites containing resources (a burrow) that are also used by females. Lizards frequently rely on chemical cues to detect the presence of a conspecific. Male lizards in particular, may chemically sample potential refuges to avoid rivals. Barking geckos were equally likely to use an artificial refuge scented by another male compared to a control, indicating that males do not use scent when selecting refuges. I assessed the role of two signals, one acoustic (dominant call frequency) and one visual (yellow throat patch), in advertising residency and aggressive behavior in barking geckos. Larger males defended the largest home ranges and home ranges were maintained through calling, which is negatively correlated with body size. Body size also predicted some behavioural responses to field-playback trials. Small males retreated from the playback and large males were found to be aggressive towards the playback. Small relative throat patch size was also correlated with aggression and charging the playback. Finally, call frequency was correlated with the behaviour of charging the playback. I suggest that the frequencies of barking gecko calls constitute a long-range signal of body size, used by males for remote rival assessment and to advertise home range boundaries. I also assessed the role of multiple signals (acoustic and visual) in reproductive success and I studied the effect of one mechanism of sexual selection, endurance iv rivalry, on reproductive success. Activity levels were similar for males which bred compared to those that did not breed, suggesting that endurance rivalry is not a significant mechanism of sexual selection in this population. Body size was the best predictor of reproductive success, suggesting that call frequency functions as a long range signal of body size used by females to assess potential mates.

In the natural world, animals encounter terrestrial environments that range from stiff to compliant. Terrestrial locomotion across natural surfaces is highly complex, as animals must overcome substrate heterogeneity to maintain locomotor performance essential for survival (e.g., catching prey, escaping predators). Within these environments, natural substrates such as sand, gravel and cobbles, are known as granular media: a collection of discrete particles varying in material properties and behaviors when exposed to forces of different magnitude. On a single step, granular media alternates between solid and fluid-like states with potentially drastic consequences on running performance. Additionally, granular substrates at different inclinations are ubiquitous in natural environments, such as sand dunes in the desert. At the angle of repose—the maximum angle providing sand dunes their typical shape—granular media will fluidize with the slightest stress, rendering running at these angles extremely challenging. Unlike locomotion through fluids (e.g., swimming and flying), governed by the Navier-Stokes equations, how foot kinematics instigate state changes on granular media is still poorly understood, yet it is critically important for survival. The goal of my dissertation is to determine how foot use affects foot-ground interactions on granular media, with a particular focus on incline locomotion. The objectives of my dissertation are threefold: evaluate the effects of granular inclines on 1) performance and above-surface limb and foot kinematics, 2) sub-surface foot kinematics, and 3) the dynamics of foot-ground interactions using computational simulations. To fulfill these objectives, I examined three lizard species: a sand specialist (Callisaurus draconoides), a desert generalist (Crotaphytus bicinctores), and a fluid specialist (Basiliscus vittatus), selected because they have similarly shaped feet, so that differences detected among performance are due to foot kinematics rather than morphology. I ran these lizard species on a level and inclined granular trackway, while videorecording them at 500 fps using a high-speed video camera (light video) and a bi-planar high-speed fluoroscopy system (X-ray video) for the above-surface kinematics and the subsurface kinematics, respectively. Running trials were used to quantify running speed, basic stride, foot impact, and sub-surface foot kinematics, to implement on computational simulations of foot-shaped intruders entering a volume of particles to quantify force response at the particle scale. Sand specialists not only outperformed non-specialists on the incline, but maintained running speed compared to the level despite presenting some foot slip. While no significant differences across species were found for basic stride and impact kinematics, only sand specialists shifted foot intrusion angle into incline granular media to angles close to perpendicular to the substrate. At the subsurface, sand specialists maintained a stiffer foot similar to generalists, and intruded their feet shallower similar to fluid specialists. However, only sand specialists maintained toe spacings close to 6 mm on level and incline, similar to a study on intruder spacings showing peak force generation. The ground force response exhibited by the sand specialist lizard foot model revealed that by hitting the particles fast (0.7 m/s) and shallow, almost perpendicular to the substrate, toe first, with stiff feet, and toe spacings close to 6 mm, sand specialists are likely taking advantage of the inertial behavior of the particles at the angle of repose. Essentially, by paddling through the substrate’s fluid-like behaving surface, sand specialists run significantly faster than fluid specialists and generalists. My dissertation demonstrates the significance of surface and subsurface kinematics strategies to understand foot-ground interactions, especially on angled yielding substrates, contributing with knowledge to the terradynamics field and elucidating significant applications in bioengineering, bioinspiration and robotics. / Biology