As water is essential for survival, seasonal scarcity of freshwater resources can pose a challenge for many species. In xeric environments, efficient location of ephemeral water is crucial to capitalize on this rare, critical resource. Yet little is known about how organisms locate water, though it has been acknowledged that olfactory spatial navigation may benefit water searching in xeric-adapted species. Additionally, drinking behavior may be influenced by water salinity as consuming water with salinity levels that exceed blood osmolality can induce or exacerbate dehydration. To investigate whether animals can locate water via olfaction, whether salinity affects the amount of water consumed, and whether the extent of dehydration affects both processes, I conducted three experiments in a xeric-adapted reptile, the Gila monster (Heloderma suspectum). Two experiments used a T-maze to examine the effects of various olfactory cues and hydration state on spatial navigation to water resources, while the third experiment examined willingness to drink water of various salinity levels depending on the extent of dehydration. I found that Gila monsters accurately navigated to olfactory cues associated with aged tap water, but not other olfactory cues (pond water, geosmin/MIB, IBMP/IPMP). Increased extent of dehydration correlated with greater spatial navigation efficiency but did not meaningfully impact navigation accuracy. Moderately dehydrated Gila monsters selectively consumed water with lower salinity levels (freshwater, 1,250 ppm, and 2,500 ppm) and avoided highly saline water resources (10,000 ppm and 20,000 ppm). However, considerably dehydrated animals demonstrated an increased propensity to consume water with higher salinity levels. These results provide evidence for olfactory spatial navigation and selective consumption of saline water as strategies to locate water and efficiently osmoregulate in an osmotically challenging environment. These findings underscore the observed adaptable physiological and behavioral traits Gila monsters and other xeric-adapted species use to endure the seasonal water limitations.

Environmental variation impacts physiological performance in animals. As a result, many animals thermoregulate to buffer unfavorable thermal variation in their environments. Animals are only expected to thermoregulate when the benefits outweigh the costs, although both are difficult to quantify. I examined how habitats and organismal factors shape thermoregulation and physiological performance in lizards. I found that habitat structure shapes opportunities for thermoregulation in two species of Anolis lizards. In dense tropical rainforests where there is low habitat heterogeneity, the range of available microclimates is narrow. Consequently, lizards in the tropics tend to be thermal specialists – performing best over a narrow range of temperatures. This phenotype should lead to decreased performance under climate warming. I then investigated the relationship between body condition, feeding, and thermoregulation in Yarrow’s spiny lizards (Sceloporus jarrovii) using lab- and field-based experiments. In the lab experiment, when lizards were observed in an artificial thermal gradient, neither body condition nor feeding status influenced the mean body temperature. When simulated costs of thermoregulation were higher, all lizards reduced thermoregulation similarly. However, when lizards were observed in an outdoor thermal arena, individuals with lower body condition decreased thermoregulatory performance, resulting in a lower mean body temperature. Animals with poor body condition may face greater risk of predation when thermoregulating. Finally, I conducted a comparative analysis to quantify relationships between the potential for thermoregulatory performance and empirical measures of productivity (i.e., growth rates and reproductive output) in lizard populations. A model that assumes lizards are active whenever preferred temperatures were available overestimated the duration that a lizard could maintain a preferred body temperature. As such, studies equating predicted thermoregulatory performance with fitness in the context of climate change should be interpreted cautiously. Overall, environmental factors and organismal traits shape the thermoregulatory behavior of animals, ultimately affecting their physiological performance and fitness. Biologists should consider these relationships when modeling the impacts of climate change on future performance.

Though the connection between terrestrial riparian consumers and the adjacent aquatic food web has been well-studied in a variety of systems, gaps with respect to several habitats remain. The Colorado River Basin represents many of these untested habitat characteristics: it contains large, controlled rivers in an arid environment that are often canyon-bound. These characteristics, however, are not unique to the Colorado River Basin. Dams and arid lands are becoming increasingly common around the world, stressing the importance of understanding the function of riparian areas within the Colorado River Basin and basins like it. Stable isotopes, including the more recent application of deuterium, can be used to elucidate trophic linkages between rivers and their riparia. Though dams may harm aquatic insect populations, it is possible that they also make aquatic insects a stable, constant food source to the riparian biological community. This dissertation demonstrates that aquatic emergent insects are a reliable, and therefore important, food source for arid land riparian consumers along regulated rivers. However, the importance of aquatic emergent insects to riparian consumers may vary across sites, even within the same river basin. To explore this variation, the diet of a common riparian lizard species Urosaurus ornatus (Ornate Tree Lizard) can be used as an indicator of cross-ecosystem connectivity. This dissertation demonstrates linkages between two differing river segments and U. ornatus, showcasing its ability as an indicator of connectivity across a diversity of systems. Within the Colorado River Basin, the Grand Canyon provides an opportunity to study a variety of riparian consumers across a gradient of habitat parameters and dam effects. This dissertation demonstrates the manifold connections between large, regulated rivers and arid riparian consumers, ranging from lizards, to bats, to, for the first time, mice. Monsoons have differing effects on river-riparian communities in this basin, potentially related to intact tributary confluences. Lastly, this dissertation demonstrates that hydropeaking reduces river-riparia connectivity by reducing aquatic insect emergence. This dissertation seeks to improve understanding of the linkages between river and their riparia to aid in the management of arid riparian areas affected by dams worldwide.

August Krogh, a 20th century Nobel Prize winner in Physiology and Medicine, once stated, "for such a large number of problems there will be some animal of choice, or a few such animals, on which it can be most conveniently studied." What developed to be known as the Krogh Principle, has become the cornerstone of bioinspired robotics. This is the realization that solutions to various multifaceted engineering problems lie in nature. With the integration of biology, physics and engineering, the classical approach in solving engineering problems has transformed. Through such an integration, the presented research will address the following engineering solution: maneuverability on and through complex granular and aquatic environments. The basilisk lizard and the octopus are the key sources of inspiration for the anticipated solution. The basilisk lizard is a highly agile reptile with the ability to easily traverse on vast, alternating, unstructured, and complex terrains (i.e. sand, mud, water). This makes them a great medium for pursuing potential solutions for robotic locomotion on such terrains. The octopus, with a nearly soft, yet muscular hydrostat body and arms, is proficient in locomotion and its complex motor functions are vast. Their versatility, "infinite" degrees of freedom, and dexterity have made them an ideal candidate for inspiration in the fields such as soft robotics. Through conducting animal experiments on the basilisk lizard and octopus, insight can be obtained on the question: how does the animal interact with complex granular and aquatic environments so effectively? Following it through by conducting systematic robotic experiments, the capabilities and limitations of the animal can be understood. Integrating the hierarchical concepts observed and learnt through animal and robotic experiments, it can be used towards designing, modeling, and developing robotic systems that will assist humanity and society on a diversified set of applications: home service, health care, public safety, transportation, logistics, structural examinations, aquatic and extraterrestrial exploration, search-and-rescue, environmental monitoring, forestry, and agriculture, just to name a few. By learning and being inspired by nature, there exist the potential to go beyond nature for the greater good of society and humanity.

Free-choice learning environments provide visitors with unique opportunities to observe and learn voluntarily and can serve as valuable educational opportunities. Incorporating interactive elements into displays have been shown to increase visitor dwell time and, ultimately, enhance the displays’ impacts on visitor knowledge and positive attitudes. This is especially important in free-choice learning environments where the visitor controls what display to visit and for how long. Visitors may not benefit from the display if they are not engaged with some attention-holding component. Interactive elements can greatly benefit a display’s potential to strengthen a visitor’s conservation attitudes and values of non-charismatic species that are traditionally less engaging due to their lack of activity or their appearance. This study examined the effect of a self-guided display with or without the incorporation of interactive elements on a visitors knowledge, attitude, and value of rattlesnakes. In Spring 2019, university biology students took surveys before (pre-survey) and after (post-survey) visiting a live animal rattlesnake display on campus. This was repeated in the Fall 2019 except that eight interactive elements were incorporated into the rattlesnakes displays. The pre and post-surveys were designed to evaluate the effect of the displays on student knowledge, attitudes, and values towards rattlesnakes. Paired t-tests revealed that visiting the displays increased student knowledge, attitude, and value of rattlesnakes, but that this effect was not enhanced by adding the interactive elements to the display. The results also showed that visiting the displays increased visitor dwell time, positively influenced one’s interest in revisiting the displays, and, overall provided visitors with enjoyment. These results provide further evidence that self-guided, live animal displays are impactful on increasing visitor knowledge, attitude, and value. However, the results also demonstrate that interactive elements do not necessarily enhance a display’s value, so further research should be conducted to determine key traits of effective interactive elements. This data and that from future related studies can have powerful conservation implications by informing on how displays can be optimized to achieve desired objectives.

Reproductive hormones are recognized for their diverse functions beyond reproduction itself, including a vital role in brain organization, structure, and function throughout the lifespan. From puberty to reproductive senescence, the female is characterized by inherent responsiveness to hormonal cyclicity. For most women, a natural transition to menopause occurs in midlife, wherein the endogenous hormonal milieu undergoes significant changes and marks the end of the reproductive life stage. Although most women experience natural menopause, many women will undergo gynecological surgery during their lifetime, which can lead to an abrupt surgical menopause. It is of critical importance to better understand how endogenous and exogenous reproductive hormone exposures across the lifespan influence cognitive and brain aging, as women are at a greater risk for developing a variety of diseases after menopause, including dementia. Using rodent models, this dissertation explores how the etiology of reproductive senescence, that is, whether it is transitional or surgical, influences the female phenotype to result in divergent cognitive outcomes dependent upon a variety of factors, with an emphasis on age at the time of intervention playing a key role in brain outcomes. Furthermore, the impact of exogenous hormone therapy on cognition is evaluated in the context of surgical menopause. A novel rat model of hysterectomy is also presented, with results demonstrating for the first time that the nonpregnant uterus, which is typically considered to be a quiescent organ, may play a unique, direct role in modulating cognitive outcomes. Neurobiological mechanisms associated with reproductive hormones and aging are assessed to better recognize neural correlates underlying the observed behavior changes. The overarching goal of this dissertation was to elucidate novel factors contributing to cognitive aging outcomes in females. Collectively, the data presented herein indicate that the age at the onset of reproductive senescence has significant implications for learning and memory outcomes, and that variations in gynecological surgery can have unique, long-lasting effects on the brain and cognition. Translationally, this series of experiments moves the field forward toward the goal of improving the health and quality of life for women throughout the lifespan.

Environmental changes are occurring at an unprecedented rate, and these changes will undoubtedly lead to alterations in resource availability for many organisms. To effectively predict the implications of such changes, it is critical to better understand how organisms have adapted to coping with seasonally limited resources. The vast majority of previous work has focused on energy balance as the driver of changes in organismal physiology. While energy is clearly a vital currency, other resources can also be limited and impact physiological functions. Water is essential for life as it is the main constituent of cells, tissues, and organs. Yet, water has received little consideration for its role as a currency that impacts physiological functions. Given the importance of water to most major physiological systems, I investigated how water limitations interact with immune function, metabolism, and reproductive investment, an almost entirely unexplored area. Using multiple species and life stages, I demonstrated that dehydrated animals typically have enhanced innate immunity, regardless of whether the dehydration is a result of seasonal water constraints, water deprivation in the lab, or high physiological demand for water. My work contributed greatly to the understanding of immune function dynamics and lays a foundation for the study of hydration immunology as a component of the burgeoning field of ecoimmunology. While a large portion of my dissertation focused on the interaction between water balance and immune function, there are many other physiological processes that may be impacted by water restrictions. Accordingly, I recently expanded the understanding of how reproductive females can alter metabolic substrates to reallocate internal water during times of water scarcity, an important development in our knowledge of reproductive investments. Overall, by thoroughly evaluating implications and responses to water limitations, my dissertation, when combined previous acquired knowledge on food limitation, will enable scientists to better predict the impacts of future climate change, where, in many regions, rainfall events are forecasted to be less reliable, resulting in more frequent drought.

Sexual and social signals have long been thought to play an important role in speciation and diversity; hence, investigations of intraspecific communication may lead to important insights regarding key processes of evolution. Though we have learned much about the control, function, and evolution of animal communication by studying several very common signal types, investigating rare classes of signals may provide new information about how and why animals communicate. My dissertation research focused on rapid physiological color change, a rare signal-type used by relatively few taxa. To answer longstanding questions about this rare class of signals, I employed novel methods to measure rapid color change signals of male veiled chameleons Chamaeleo calyptratus in real-time as seen by the intended conspecific receivers, as well as the associated behaviors of signalers and receivers. In the context of agonistic male-male interactions, I found that the brightness achieved by individual males and the speed of color change were the best predictors of aggression and fighting ability. Conversely, I found that rapid skin darkening serves as a signal of submission for male chameleons, reducing aggression from winners when displayed by losers. Additionally, my research revealed that the timing of maximum skin brightness and speed of brightening were the best predictors of maximum bite force and circulating testosterone levels, respectively. Together, these results indicated that different aspects of color change can communicate information about contest strategy, physiology, and performance ability. Lastly, when I experimentally manipulated the external appearance of chameleons, I found that "dishonestly" signaling individuals (i.e. those whose behavior did not match their manipulated color) received higher aggression from unpainted opponents. The increased aggression received by dishonest signalers suggests that social costs play an important role in maintaining the honesty of rapid color change signals in veiled chameleons. Though the color change abilities of chameleons have interested humans since the time of Aristotle, little was previously known about the signal content of such changes. Documenting the behavioral contexts and information content of these signals has provided an important first step in understanding the current function, underlying control mechanisms, and evolutionary origins of this rare signal type.

Social structure affects many aspects of ecology including mating systems, dispersal, and movements. The quality and pattern of associations among individuals can define social structure, thus detailed behavioral observations are vital to understanding species social structure and many other aspects of their ecology. In squamate reptiles (lizards and snakes), detailed observations of associations among individuals have been primarily limited to several lineages of lizards and have revealed a variety of social structures, including polygynous family group-living and monogamous pair-living. Here I describe the social structure of two communities within a population of Arizona black rattlesnakes (Crotalus cerberus) using association indices and social network analysis. I used remote timelapse cameras to semi-continuously sample rattlesnake behavior at communal basking sites during early April through mid-May in 2011 and 2012. I calculated an association index for each dyad (proportion of time they spent together) and used these indices to construct a weighted, undirected social network for each community. I found that individual C. cerberus vary in their tendency to form associations and are selective about with whom they associate. Some individuals preferred to be alone or in small groups while others preferred to be in large groups. Overall, rattlesnakes exhibited non-random association patterns, and this result was mainly driven by association selection of adults. Adults had greater association strengths and were more likely to have limited and selected associates. I identified eight subgroups within the two communities (five in one, three in the other), all of which contained adults and juveniles. My study is the first to show selected associations among individual snakes, but to my knowledge it is also the first to use association indices and social network analysis to examine association patterns among snakes. When these methods are applied to other snake species that aggregate, I anticipate the `discovery' of similar social structures.