Sceloporus Graciosus Research Articles

Contextualized Display Behavior during Natural Interactions by Common Side-Blotched Lizards (Uta stansburiana, Squamata, Phrynosomatidae)

Many previous studies on competition focused on outcomes of competition and less on behavioral changes during or immediately following intra- or interspecific interactions. I performed 300 h of observation of three lizard species (Side-blotched Lizards, Uta stansburiana; Sagebrush Lizards, Sceloporus graciosus; Western Fence Lizards, Sceloporus occidentalis) and recorded 1,045 natural encounters, 403 of which were unconfounded by presence of another individual lizard. Despite potential competition amongst these species, I found little evidence that Uta modify perch characteristics or engage in aggressive interactions toward either of the heterospecific lizards. However, Uta do alter interspecific display behavior depending on whether interactions are intrasexual or intersexual. Moreover, Uta move shorter distances following interactions with S. graciosus but greater distances after interactions with S. occidentalis. Uta appear to reserve aggressive or more-intense interactions for intersexual intraspecific encounters, most of which are initiated by males. Together these findings suggest that these three lizard species are not broadly engaged in competitive interactions and that habitat characteristics or microhabitat preferences enable co-occurrence.

Apparent Predation by Rock Wren of Common Sagebrush Lizard

Apparent Predation by Rock Wren of Common Sagebrush Lizard

From the ground up: microhabitat use within a landscape context frames the spatiotemporal scale of settlement and vacancy dynamics in an endemic habitat specialist

Understanding how species are distributed throughout landscapes requires knowledge of the hierarchy of habitat selection made by individuals, the resulting spatiotemporal structure of demography, and the consequent dynamics of localized populations. We examined how patterns of habitat use, settlement, and vacancy in an endemic habitat specialist, Sceloporus arenicolus (dunes sagebrush lizard), varied within the Mescalero Monahans Sandhills ecosystem. We used a 4-year mark-recapture dataset to develop occupancy models that identified whether microhabitat or landscape scale best predicted S. arenicolus spatiotemporal habitat use, settlement, and vacancy, in both an undisturbed and disturbed landscape. Our results showed areas of high quality habitat were used constantly and lower quality areas were used intermittently, but repeatedly, over time in the undisturbed landscape. Habitat use in the disturbed landscape was spatiotemporally unpredictable. Microhabitat variables characterizing dune landscape topography predicted probability of use in S. arenicolus, while landscape-scale variables predicted probabilities of settlement and vacancy. In the undisturbed landscape, future settlement was predicted by presence of S. arenicolus, a pattern consistent with fine-scale source-sink dynamics already described for this species. Our results illustrate how spatially-discrete but temporally-linked areas should be conserved at fine spatiotemporal scales to secure persistence of S. arenicolus populations under variable environmental conditions. Disturbances to habitat continuity can disrupt individual movements and create inconsistently occupied habitat patches that appear to be unoccupied and thus are threatened by further disturbances.

RESPONSES OF A MONTANE LIZARD ASSEMBLAGE TO AN EXTENDED DROUGHT

Modern climate change will increase temperatures, as well as the frequency and severity of droughts and wildfires across the semiarid montane regions of the southwestern United States. Predictions of reduced habitat suitability and increases in extinctions precipitated by climate change derive from modeled responses to these conditions, especially increased temperatures. What is often lacking are empirical tests of those modeled predictions. Here I report findings from surveys of montane lizard assemblages during a period of increased temperatures, extended drought, and including a wildfire. I selected survey routes that included upper-elevation limits for western fence lizards (Sceloporus occidentalis), granite spiny lizards (Sceloporus orcuttii), and side-blotched lizards (Uta stansburiana), as well as the lower limits for southern sagebrush lizards (Sceloporus vandenburgianus), to measure the extent to which habitat occupancy shifted as drought conditions changed over 4 years. At the onset of drought, the abundance of all species declined. After initial declines, populations stabilized and I observed recruitment, positive population growth, and elevation shifts with only modest increases in rainfall. Once the drought abated, there were further increases in recruitment and population growth, but a colder winter and heavy snows in 2017 were coincident with declines and range contractions in both western fence and side-blotched lizards on the higher-elevation survey route. There was no indication that any of these species' populations were at risk of local extinctions; rather, shifts at range margins and use of microclimates revealed resilience and mechanisms of how these species might deal with future conditions, including occupying climate refugia.

Bias and Precision of Lizard Occupancy Estimates Vary among Observers and between Methods

Heterogeneity in detection probabilities arises from many parts of a survey design and can introduce bias into estimates of site occupancy probability. We examined the effect of two important sources of heterogeneity, observer and survey method, on occupancy estimates in a lizard community in west Texas, with a special emphasis on Dunes Sagebrush Lizard (Sceloporus arenicolus). Using line transects and visual encounter surveys, nine observers surveyed 72 sites. We detected 10 species of lizards in total; all 10 were detected using visual encounter surveys and only 4 were detected using transects. We determined observers to be an important variable in occupancy models for two of three species of lizards. Insufficient detections were made of the remaining seven species to reliably model occupancy. We conducted simulations to further investigate the impacts of observer variability on occupancy estimate bias and precision by using a range of known occupancy and detectability combinations. Precision in the occupancy estimate increased as the mean observer detection probability increased. Overall, bias was minimized by conducting surveys with either 1) observers with high detection probabilities or 2) using teams of observers with mixed (high and low) detection probabilities.Modeling observer detection probabilities explicitly provided marginal improvement to the occupancy estimate in the simulations. The consistent variability in detection probability among observers has implications for the precision and bias in occupancy estimates and decisions should be made at the experimental design phase about how to approach this problem.

Fragmentation alters home range and movements of the Dunes Sagebrush Lizard (Sceloporusarenicolus)

Habitat fragmentation is a major driver of biodiversity loss and among reptiles has been attributed as a cause of species decline. The negative effect of habitat fragmentation has also been shown to be worse for species that are habitat specialists. The Dunes Sagebrush Lizard (Sceloporus arenicolus Degenhardt and Jones, 1972) is a species that specializes on the shinnery oak (Quercus havardii Rydb.) sand-dune landform of the Mescalero–Monahans Sandhills ecosystem in western Texas and eastern New Mexico, USA. This landform has been fragmented by roads and well pads used for the extraction of oil and gas resources. The effects of fragmentation on the home range and movements of this species can lead to the effective isolation of populations and increased risk of localized extirpations. We showed that home-range size was larger in an unfragmented area and that the mean distance of movements was greater. We also observed that roads in the fragmented areas restricted movements of S. arenicolus. We concluded that roads can be barriers to movements even though only narrow strips of habitat are altered.

Effects of habitat fragmentation on population structure of dune‐dwelling lizards

AbstractLandscape fragmentation alters biotic and abiotic characteristics of landscapes, variously affecting the size and demographic structure of species' populations. Fragmentation is predicted to negatively impact habitat specialists because of perturbations to their habitat, whereas generalists should be less sensitive to fragmentation. Differences in life history among the lizards in this community should partly explain some of the variation in generalist species' responses to fragmentation. During five seasons (2009–2013), we captured eight species of lizards on 27 independent trapping grids located in unfragmented (N = 18) and fragmented (N = 9) grids in the Mescalero‐Monahans Sandhills ecosystem in southeastern New Mexico. Using a two‐way ANOVA, we tested for effects of fragmentation and year on capture rates for each species. To test for effects of fragmentation on demographic structure, we used contingency tables with expected frequencies computed from the demographic structure on unfragmented grids. Capture rates of the endemic habitat specialist Sceloporus arenicolus (dunes sagebrush lizard) decreased to zero in fragmented sites. The demographic structure of S. arenicolus and Holbrookia maculata (common lesser earless lizard) was severely disrupted at fragmented sites, with proportions of juveniles, adult males, or adult females being over‐ or underrepresented during sample months. Variable responses of five generalist species could be attributed to life history patterns, habitat affinity, and breeding phenology. This is the first empirical study we are aware of that describes and quantifies the demographic effects of fragmentation on populations of multiple lizard species in a replicated study. Our findings lend important insights into how habitat specialization and differences in life history influence the susceptibility of species to the impacts of fragmentation.

Why didn't the lizard cross the road? Dunes sagebrush lizards exhibit road-avoidance behaviour

Context Research has shown many negative effects of roads and traffic on wildlife and other biodiversity. The direct and indirect mechanisms through which roads and traffic harm animal populations vary across taxa, making mitigation of road effects a great challenge for conservation. As such, a large toolkit of species-specific management techniques may be needed to mitigate the negative effects of roads for wildlife and other biodiversity. The dunes sagebrush lizard, Sceloporus arenicolus, is a psammophilic (sand-loving) habitat specialist endemic to the Mescalero–Monahans Sandhills ecosystem of New Mexico and Texas. Within this ecosystem, roads fragment shinnery oak sand-dune landforms occupied by the species. Aims In the present study, we conducted behaviour trials in experimental enclosures to test whether the smallest roads restrict movements of the dunes sagebrush lizard. In addition, we also conducted trials to evaluate whether a sand-filled wildlife-crossing feature could facilitate road crossing. Methods We conducted behavioural trials on 24 dunes sagebrush lizards in our control enclosure and 22 lizards in our road and sand-filled wildlife-crossing enclosure. Movements were recorded for 15min. The final locations at the end of each trial were analysed using circular statistics to determine whether movements in the road or the sand-filled wildlife-crossing enclosures were different from the control. Key results Our results supported the hypotheses that dunes sagebrush lizards avoid roads and do so according to a surface-avoidance mechanism. We also found that the wildlife crossing-feature design tested here had no effect on the movements or road-crossing frequency of dunes sagebrush lizard. Conclusions Surface-avoidance behaviour indicated that roads will persistently affect the movements of dunes sagebrush lizard, even when traffic is not present. Also, more research into an effective wildlife crossing is needed to increase connectivity of fragmented populations. Implications These findings help evaluate the impact of roads in creating isolated populations that experience increased demographic stochasticity and, in some instances, localised extirpation in this species. Our study can guide conservation plans for the dunes sagebrush lizard, and contribute to our understanding of road effects on biodiversity in general.

Conservation Credits—Evolution of a Market-Oriented Approach to Recovery of Species of Concern on Private Land

When species are listed as threatened or endangered under the Endangered Species Act, there are often real or perceived negative consequences for landowners that may produce perverse incentives and lead to the elimination rather than protection of habitat for the species on private land. In Texas, where approximately 95% of the land is privately owned, the listing of one species and the potential listing of another led to the creation of two innovative programs aimed at incentivizing landowners to protect and improve habitat for the two species: Recovery Credit System for the Golden-Cheeked Warbler and Conservation Recovery Award System for the Dunes Sagebrush Lizard. Both programs were based on multistakeholder collaborations that included federal and state agencies, nongovernmental organizations, and private landowners, and which resulted in quasimarket mechanisms for the voluntary protection of habitat by landowners for the species of concern. Key components of both programs included confidentiality of landowner conservation agreements with the state’s wildlife management agency and the creation of not-for profit organizations to implement contracts with landowners and disseminate payments for habitat conservation actions to landowners. These two programs have also informed efforts to protect the Lesser Prairie-Chicken and Greater Sage-Grouse, which are under threat on private land in multiple states. Seven lessons learned from protection programs for the four species presented in this article provide useful guidelines for the conservation of other at-risk species on private land elsewhere.

The Relative Influence of Road Characteristics and Habitat on Adjacent Lizard Populations in Arid Shrublands

Abstract As road networks continue to expand globally, indirect impacts to adjacent wildlife populations remain largely unknown. Simultaneously, reptile populations are declining worldwide and anthropogenic habitat loss and fragmentation are frequently cited causes. We evaluated the relative influence of three different road characteristics (surface treatment, width, and traffic volume) and habitat features on adjacent populations of Northern Sagebrush Lizards (Sceloporus graciosus graciosus), Plateau Fence Lizards (S. tristichus), and Greater Short-Horned Lizards (Phrynosoma hernandesi) in mixed arid shrubland habitats in southwest Wyoming. Neither odds of lizard presence nor relative abundance was significantly related to any of the assessed road characteristics, although there was a trend for higher Sceloporus spp. abundance adjacent to paved roads. Sceloporus spp. relative abundance did not vary systematically with distance to the nearest road. Rather, both Sceloporus spp. and Greater Short-Horned Liz...

Daily and Seasonal Patterns of Natural Ultraviolet Light Exposure of the Western Sagebrush Lizard (Sceloporus graciosus gracilis) and the Dunes Sagebrush Lizard (Sceloporus arenicolus)

Abstract: We monitored ultraviolet-B (UVB) irradiance exposure (measured using the ultraviolet index [UVI]) of the Western Sagebrush Lizard (Sceloporus graciosus gracilis) in Lassen Volcanic National Park, California, and the related Dunes Sagebrush Lizard (S. arenicolus) in eastern New Mexico. For S. graciosus gracilis, on sunny days between 0900 and 1100 h, average lizard UVI tracked available solar UVI. Periodic shade-seeking between 1100 and 1600 h resulted in lizard UVI being less than the available solar UVI. This daily pattern of exposure was evident for the activity period from June until August. This general pattern was also evident for S. arenicolus except when air temperatures exceeded 37°C; at these times, all S. arenicolus subjects retreated underground for much of the afternoon. Individuals of S. graciosus gracilis exhibited large within-day variations in the durations of time that they basked in full sun, sought shade, and retreated underground. Two lizards followed for most of a day showe...

Endangered Species in the Oil Patch

Tension among competing interests is nothing new in environmental law. Even among the most tenacious adversaries, the ability to find common ground can serve as an impetus to further the aims of both industry and environmental proponents. Broadly speaking, advocates of the oil and gas industry prefer few restraints, if any, on exploration, development, and production. Comparatively, champions of biological and ecological preservation favor regulatory protections to conserve these interests. Cutting across these often disparate objectives, the Endangered Species Act (ESA) presents a not-so-obvious opportunity for both sides to receive a share of the pie through cooperation and forward planning. This Paper proffers the notion that where concerns over the survival of a species may impede oil and gas activities, proactive cooperation, planning, and compromise within the ESA process can present both industry and environmentalists with a winning outcome. The Paper first provides background information on the ESA and describes its chief statutory mechanics. Next, the Paper discusses recent ESA developments that are particularly relevant to the oil and gas industry and focuses on the cooperative effort related to the Dunes Sagebrush Lizard and pursued by the oil and gas industry, private landowners, state officials in Texas and New Mexico, and environmental organizations. Finally, the Paper reviews pending ESA issues and offers recommendations for private and public stakeholders facing ESA challenges.

Review of the systematic status of Sceloporus arenicolus Degenhardt and Jones, 1972 with an estimate of divergence time.

The sagebrush lizards (Sceloporus graciosus group) consist of four taxa (S. graciosus graciosus, S. graciosus gracilis, S. graciosus vandenburgianus, and S. arenicolus) distributed in western North America. Of these, S. arenicolus is morphologically, behaviorally, and ecologically distinct as well as geographically disjunct from the other taxa, occurring only in the Mescalero-Monahans Sandhills of southeastern New Mexico and adjacent Texas. Sceloporus arenicolus is a taxon of concern because of its small range and habitat alteration due to land use practices. Understanding evolutionary relationships among members of the S. graciosus group, and especially S. arenicolus, has important implications for conservation. We examine the phylogenetic relationship of S. arenicolus relative to the three recognized subspecies of S. graciosus at mitochondrial and nuclear loci for populations sampled throughout the ranges of these taxa. Additionally, we estimate the divergence time and clade age of S. arenicolus. We find that the S. graciosus group is in need of major taxonomic revision, and also confirm that S. arenicolus is a genetically distinct and divergent lineage. These results bear important consequences for conservation and management.

Male Sagebrush Lizards (Sceloporus graciosus) Increase Exploratory Behavior Toward Females with More Courtship Experience

Courtship is an essential component to male reproductive success. Most males must identify and court appropriate females to enhance their fitness. At the same time, female reproductive state and investment is influenced by the quality of male courtship. In this experiment, we test whether the amount of female courtship experience influences the behavior of males interacting with those females in sagebrush lizards, Sceloporus graciosus. We used a robotic lizard to present male courtship displays to females, presenting females with displays either every other day (low quantity) or four times daily (high quantity). After 2 wk of courtship experience, we placed a live male into the home terrarium of each female and recorded interactions for 30 min, scoring both male and female behavior from these recordings. Males exhibited more movements and chemoreceptive behavior toward females that had received more courtship experience, showing that they could detect an effect. We did not detect any difference in female behavior between groups. Future work is needed to identify physiological differences between females differing in courtship experience. Our study also confirms the utility of a robotic lizard in understanding lizard behavior and expands the use of robotic stimuli outside of the context of playback experiments.

Food supplementation and testosterone interact to influence reproductive behavior and immune function in Sceloporus graciosus

The energetic resources in an organism's environment are essential for executing a wide range of life-history functions, including immunity and reproduction. Most energetic budgets, however, are limited, which can lead to trade-offs among competing functions. Increasing reproductive effort tends to decrease immunity in many cases, and increasing total energy via supplemental feedings can eliminate this effect. Testosterone (T), an important regulator of reproduction, and food availability are thus both potential factors regulating life-history processes, yet they are often tested in isolation of each other. In this study, we considered the effect of both food availability and elevated T on immune function and reproductive behavior in sagebrush lizards, Sceloporus graciosus, to assess how T and energy availability affect these trade-offs. We experimentally manipulated diet (via supplemental feedings) and T (via dermal patches) in males from a natural population. We determined innate immune response by calculating the bacterial killing capability of collected plasma exposed to Escherichia coli ex vivo. We measured reproductive behavior by counting the number of courtship displays produced in a 20-min sampling period. We observed an interactive effect of food availability and T-patch on immune function, with food supplementation increasing immunity in T-patch lizards. Additionally, T increased courtship displays in control food lizards. Lizards with supplemental food had higher circulating T than controls. Collectively, this study shows that the energetic state of the animal plays a critical role in modulating the interactions among T, behavior and immunity in sagebrush lizards and likely other species.

Inhibitory interactions between multimodal behavioural responses may influence the evolution of complex signals

Most animal displays make use of multiple sensory modalities (visual, acoustic and chemical signals) to convey similar information. Although multimodal displays may allow producers to use displays in a wider variety of social and physical contexts, it is difficult to explain their evolution because of the likely increased costs to senders and receivers. In this study, playback experiments in two contexts were used to study the behavioural responses to visual (headbob displays) and chemical (femoral pore secretions) signals in sagebrush lizards, Sceloporus graciosus. Lizards in the field tended to headbob in response to headbob displays and to engage in chemical exploratory behaviour when presented with chemical secretions. Territorial residents produced fewer headbob displays and head-turns in response to a combined signal produced by a robotic lizard than they did to either signal presented alone. This inhibition was confirmed in the laboratory, where presentation of a visual stimulus alone decreased chemical exploratory behaviour and presentation of a chemical stimulus alone decreased the number of headbob displays produced. The absolute cost of this interaction between sensory modalities may be low because the two behavioural responses are redundant, both allowing the receiver to acquire additional information, either by engaging a second lizard in a bout of interactive visual displays or by absorbing more of their scent. Thus, in sagebrush lizards, multiple signals may be evolutionarily maintained because behavioural responses to different sensory modalities are redundant and, hence, the cost of negative interactions between those responses is low.

Courtship attention in sagebrush lizards varies with male identity and female reproductive state

Previous experiments suggest that males spend more time with the more receptive of 2 novel females or the one with the higher fitness potential. However, males often court individual females repeatedly over a season; for example, male lizards sequentially visit familiar females as they patrol territorial boundaries. It may benefit males to vary display intensity as they move between multiple females. In this study, we explored the factors influencing amount of male courtship to familiar females in the sagebrush lizard, Sceloporus graciosus. We tested whether males vary the amount of courtship exhibited due to individual differences among males, female reproductive state, or female fitness potential. Each male was allowed to interact separately, but repeatedly, with 2 females until both females laid eggs. Male courtship behavior with each of the 2 females was assayed at an intermediate point, after 3 weeks of interaction. We found that individual differences among males were considerable. The number of male courtship displays was also positively correlated with female latency to lay eggs, with males displaying more often toward females with eggs that had not yet been fertilized. Courtship behavior was not well predicted by the number of eggs laid or by female width, both measures of female quality. Thus, male S. graciosus appear to alter courtship intensity more in response to signals of female reproductive state than in response to variation in potential female fitness.

Linking Traits to Energetics and Population Dynamics to Predict Lizard Ranges in Changing Environments

I present a dynamic bioenergetic model that couples individual energetics and population dynamics to predict current lizard ranges and those following climate warming. The model predictions are uniquely based on first principles of morphology, life history, and thermal physiology. I apply the model to five populations of a widespread North American lizard, Sceloporus undulatus, to examine how geographic variation in traits and life histories influences ranges. This geographic variation reflects the potential for species to adapt to environmental change. I then consider the range dynamics of the closely related Sceloporus graciosus. Comparing predicted ranges and actual current ranges reveals how dispersal limitations, species interactions, and habitat requirements influence the occupied portions of thermally suitable ranges. The dynamic model predicts individualistic responses to a uniform 3 degrees C warming but a northward shift in the northern range boundary for all populations and species. In contrast to standard correlative climate envelope models, the extent of the predicted northward shift depends on organism traits and life histories. The results highlight the limitations of correlative models and the need for more dynamic models of species' ranges.

Effects of two courtship display components on female reproductive behaviour and physiology in the sagebrush lizard

Exposure to aggressive or courtship displays of conspecifics has been shown to alter the physiology and behaviour of observers. However, these effects are dependent on the information content of signals. Separate courtship signals that convey redundant information may be expected to have similar effects on female reproductive physiology or behaviour, while those that contain nonredundant information are expected to have differing effects. Using a mechanized model lizard painted to resemble a male sagebrush lizard, Sceloporus graciosus, we presented female sagebrush lizards with either a stationary model or one of two male display types: push-ups, a signal used in both aggressive and courtship displays, and shudders, a display used exclusively during courtship. Females exposed to push-ups showed more rejection behaviour when later paired with a live male lizard and produced less femoral pore secretions on the first day of stimulus presentation than females exposed to shudders. However, females exposed to either display were found in closer proximity to the live male than females exposed to the stationary model. These results suggest that both components of the courtship display (push-ups and shudders) cause lasting but distinctive changes in female behaviour, supporting a ‘multiple messages’ scenario for the evolution of the two signals.

Display Plasticity in Response to a Robotic Lizard: Signal Matching or Song Sharing in Lizards?

AbstractMany territorial songbirds alter the structure of their songs after listening to and interacting repeatedly with the same neighbors. Here, we use a robotic lizard to test for similar learned changes in signal structure in male Sagebrush lizards, Sceloporus graciosus. Subjects were exposed to two types of headbob displays (species‐typical and unusual) both in short‐term tests and in repeated exposures for 10 d. We found no evidence for immediate changes in signal structure to match a particular opponent (signal matching) or long‐term changes after repeated exposure (‘song’ sharing). If anything, the lizards’ displays became less like that of the robotic stimulus over time. Further tests of other taxa are needed to identify the evolutionary forces that lead to these forms of behavioral plasticity and to determine whether song sharing and signal matching are unique characteristic of songbirds. Lizards also became more agitated and produced more highly aggressive displays of their own when confronted with headbob displays that violated the basic syntactic structure of their display system, confirming that they were paying attention to subtle differences in display structure despite the artificial nature of the treatments. Thus, our study also adds to the growing evidence supporting the use of robotic playbacks to study animal communication.