While the stress response represents an example of allostasis that enables the organism to cope with environmental and psychosocial challenges, its chronic activation imposes an allostatic load that contributes to the cumulative wear and tear of the system and induces negative mental and physical health outcomes. Nonetheless, the underlying basis of the stress-disease connection is still poorly understood and represents a gap in the knowledge that requires further research. We investigated the effects of chronic glucocorticoid stimulation in three independent human primary fibroblast lines, as an in vitro model of chronic psychosocial stress. By deploying a longitudinal, high-frequency, repeated-measures strategy across their entire lifespan, we were able to determine that chronically stressed cells present a significant increase in their total energy expenditure and that this stress-induced hypermetabolism is linked to an acceleration of their biological aging. Expanding from our results and placing emphasis on the energetic costs associated with the activation of the stress response, we proposed the “Energetic Model of Allostatic Load”. This model proposes that chronic stress causes a redirection of the energetic resources towards allostatic responses and away from growth, maintenance, and repair processes, which in turn leads to the accumulation of damage that will further contribute to the development of disease and increased risk of mortality. Finally, we highlighted new avenues to quantify allostatic load and its link to health via the integration of systemic and cellular energy expenditure measurements together with classic biomarkers, that could contribute to further advances in the stress field.

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Worldwide, many wildlife populations are in decline or facing extinctions due to overhunting, habitat loss and fragmentation, infrastructure development, resource extraction, and climate change. These threats are particularly detrimental to Madagascar's most iconic wildlife - lemurs (Primates: Lemuridae) – which have been declared Earth's most threatened mammal group, with 103 of 107 species currently threatened with extinction. Due to the numerous anthropogenic pressures facing lemurs, concerted efforts have been made to design and implement effective conservation management plans as well as to maintain captive populations. My dissertation focused on understanding the behavior and physiology of two critically endangered lemur species: the golden crowned sifaka (Propithecus tattersalli) and the Coquerel's sifaka (P. coquereli). To gain a better understanding of free-living golden-crowned sifaka habitat requirements, I combined behavior data with Dynamic Brownian Bridge Movement Models and Resource Selection Functions to examine the influence of abiotic, biotic, and anthropogenic factors on movement and foraging patterns. I found that movement rates and core area use were greater in the rainy season than in the dry season. My findings also indicated that roads and human villages influenced the locations where sifakas choose to forage, demonstrating the need to strategically place infrastructure to limit wildlife disturbance (Chapter 2). Second, having explored potential stressors in wild sifaka, I wanted to explore relationships between physiological stress and captive care in sifakas. Specifically, I investigated relationships between captive sifaka fecal glucocorticoid metabolite levels and captive husbandry conditions. I found that age and contraceptive use, but not enclosure type, season, or sex, influenced glucocorticoid excretion (Chapter 3). These results highlight the importance of assessing the physiological impacts of captive husbandry conditions to ensure that the best animal welfare practices can be maintained. Third, to combat challenges in studying animal behavior using observational approaches, I designed and constructed low-cost, open-source proximity loggers to remotely examine fine-scale movement and social behaviors in wild and captive sifakas. I found a relationship between radio signal strength and distance between tracking devices (R2 = 0.8812), demonstrating that proximity sensors can effectively collect data on close range group-level behavior (Chapter 4). These modular devices can be used on an array of wildlife species to explore social interactions that require high resolution spatial data. Taken together, these results illustrate the opportunity of connecting behavioral, ecological, physiological, and technological approaches to gain critical insight into the multidimensional nature of wildlife conservation. Lastly, I discussed future steps that can be taken to extend the framework established by my dissertation research to address the complex dynamics shaping conservation in Madagascar (Chapter 5). / Doctor of Philosophy / Worldwide, many wildlife populations are at risk of extinction due to hunting, habitat loss, infrastructure development, and climate change. These threats are particularly detrimental to lemurs – a diverse group of primates found only on the island of Madagascar. Due to the numerous pressures facing lemurs, efforts have been made to design and implement effective conservation management plans and maintain captive populations. My dissertation focused on understanding the behavior and physiology of two critically endangered lemur species: the golden crowned sifaka (Propithecus tattersalli) and the Coquerel's sifaka (P. coquereli). To better understand wild golden-crowned sifaka habitat needs, I followed six groups of sifakas in humid, moderate, and dry forests to examine the influence of season, forest type, and human development on their movement patterns and feeding locations. I found that sifakas moved more and used more space in the rainy season than in the dry season. Several sifaka groups also avoided feeding near roads and human villages, demonstrating the need to strategically place infrastructure to limit negative effects on wildlife (Chapter 2). Second, having explored potential stressors in wild sifaka, I wanted to explore relationships between physiological stress and captive care in sifakas. Specifically, I analyzed sifaka fecal samples to investigate relationships between captive sifaka husbandry conditions and physiological stress (i.e., glucocorticoid levels). I found that age and birth control use, but not enclosure type, season, or sex, influenced glucocorticoid levels (Chapter 3). These results highlight the importance of assessing the physiological impacts of captive husbandry conditions to ensure that the best animal welfare practices can be maintained. Third, to combat challenges in studying animal behavior using observational approaches, I designed and constructed low-cost, open-source tracking devices to remotely study fine-scale movement and social behaviors in wild and captive sifakas. I found that the distance between tracking devices can be determined by using proximity sensing radio chips. This demonstrated that proximity sensors can effectively collect data on close range group-level behavior (Chapter 4). These modular devices can be used on an array of wildlife species to explore social interactions that require high resolution spatial data. Taken together, these results illustrate the benefits of using behavioral, physiological, and technological approaches to gain insight into the multidimensional nature of wildlife conservation. Lastly, I discussed future steps that can be taken to extend the framework established by my dissertation research to address the complex dynamics shaping conservation in Madagascar (Chapter 5).

The effect of feeding colostrum or milk to newborn calves on serum cortisol, thyroxine and immunoglobulin G was investigated. Twenty-four calves (12 males and 12 females) were obtained immediately postpartum and randomly assigned to one of two rations after being blocked by breed and sex. Both rations were force-fed at birth, 12, 24 and 36 h postpartum. Blood sampling was performed at 0 time, 1, 2, 3, 4, 6 and 12 h postfeeding with this regime followed for a 48 h period (4 feedings). The average serum cortisol concentration was highest at birth, 221.9 and 245.6 ng/ml for colostrum and milk-fed calves, respectively. Cortisol levels between treatments were different (P<.05) at 2, 3, 12, 14, 18, 24, 37 and 48 h postpartum. The sex of the calf did not affect the mean cortisol concentrations. No treatment difference was observed for serum thyroxine. A sex difference was observed with the female calves exhibiting higher average thyroxine concentrations over the entire trial. A reduction in thyroxine concentration occurred with time (P<.001) as mean concentrations peaked at 4 h postpartum (22.1 μg/dl) and declined to 10.6 μg/dl by 48 h postpartum. Both treatment groups were born with similar serum immunoglobulin G levels (~0.7 mg/ml). However, at approximately 4 h postpartum, the colostrum-fed calves acquired an increase (P<.001) in serum immunoglobulin G, peaking at 24 h postpartum (26.83 mg/ml) and remaining much higher throughout the entire trial. There was a treatment difference (P<.001) between the two groups following the 4 h sample. Muscle samples (20-30g) were surgically removed from the right semitendinosus at 36 h postpartum from 14 neonatal beef calves (male and female), homogenized, and centrifuged at 105,000 x g at 4 C for 60 min. The supernatant (cytosol) was harvested and receptor quantitation, binding kinetics and ligand specificity assays were performed via [1,2,4,³H] dexamethasone. There were no binding differences between the colostrum and milk-fed calves' muscle samples. The average protein content of the muscle cytosol fraction was 50.82 mg/ml. The binding component displayed a high apparent equilibrium dissociation constant for the binding of [³H] dexamethasone (K_d = 2.34x10 ⁻⁸ ). The apparent maximum number of binding sites determined from Scatchard plots was approximately 37.61 fmol/mg of protein in the case of the dexamethasone receptor. Maximum binding appeared to reached between 16 and 24 h (48.5 and 48.2 %, respectively). Competition assays indicated all of the ligands tested had an affinity for the glucocorticoid receptor. The percent of specific binding for each was: dexamethasone (66+/-14), corticosterone (52+/-10), cortisol (58+/-13), estradiol-17, beta (37+/-7), progesterone (29+/-9), testosterone (10+/-3), and triamcinolone (41+/-11). / Master of Science

A study was conducted to determine the effects of trenbolone acetate (TBA) and estradiol-17B (E2) implantation on the characteristics of the glucocorticoid and E2 receptor, skeletal muscle protein turnover and tissue growth. Twenty-four lambs were utilized. Trenbolone acetate did not ,affect (P>.10) degradation rates in the semitendinosus (ST) and triceps brachii (TB) muscles, the production of cortisol, adrenal weights and cytosolic glucocorticoid binding capacity (Bmax). Trenbolone acetate decreased synthesis rate of muscle protein (P<.Ol), the percent of [3H] dexamethasone binding in the nuclear fraction, Bmax and the disociation constant (Kd) of the cytosolic E2 receptor, only in the TB muscle. Deoxyribonucleic acid (DNA) of the TB was increased (P<.05) with TBA. Pituitary weights were decreased (P<.005) with TBA and increased (P<.Ol) with E2. Estradiol decreased (P<.05) Bmax of the cytosolic E2 receptor in the ST and decreased (P<.05) Bmax of the nuclear E2 receptor in the TB muscle. The TB muscle had greater (P<.05) synthesis rates than the ST and the protein:RNA ratio was decreased (P<.05) in the TB. The TB muscle had greater (P<.005) Bmax for the cytosolic glucocorticoid receptor. / Master of Science

Many Neotropical felid species, such as jaguars, are threatened with extinction due to habitat fragmentation and/or human persecution. Human activities around protected areas in Belize, Central America, are increasing and so are levels of human-felid conflict. Potential consequences of this conflict are an increase in stress impacting health, diet shifts, or heightening of animal aggression. The goal of this work was to assess the effects of human-modified habitats on native felids by comparing fecal glucocorticoid metabolite (FGM) concentrations, endoparasite species richness (ESR), and diet using non-invasive scat sampling in a protected forest vs. surrounding non-protected areas in Belize. Field studies relying on non-invasive fecal hormone monitoring are subject to potential hormone degradation in samples exposed to the environment. Therefore I conducted immunoassay and environmental validations for measuring FGM in jaguars (Panthera onca). In the field, I collected scat using a detector dog, identified samples using DNA, retrieved parasite propagules with a flotation technique, and identified prey remains by morphology. I detected five felids: jaguar, puma, ocelot, jaguarundi and domestic cat. FGM concentrations were higher in pumas and jaguarundis than in the other felids. I found no livestock remains in felid scats. ESR was similar across felid species. Domestic cats were found only in human-modified areas. This results provide a baseline on adrenal activity, prey consumption, and endoparasites in felids of Belize. These findings could be used for comparisons to populations thought to be affected by human activities across Belize and in neighboring countries. / Master of Science