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).