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.

Marine plastic pollution (MPP) has emerged as one of the most pressing global environmental challenges of the anthropocene. There has been an upsurge in investment to mitigate MPP; however, interventions can be costly, inequitable, and ineffective in achieving their objectives. In my dissertation, I aim to research key considerations for creating cost-effective, equitable mitigation strategies for MPP and its impacts to marine biodiversity and coastal communities. In chapter one, I introduce the challenges plastic pollution poses. In chapter two, I use seascape ecology theory to present the concept of the plastic-scape and describe how seascape ecology principles, methods, and approaches to transdisciplinary science can inform research to mitigate MPP. In chapter three, I present a framework to help decision makers estimate the total cost of MPP interventions and partial costs accrued by stakeholder groups. I then apply this framework to two quantitative case studies and four comparative case studies to exemplify its use and highlight the ways spatial scale, temporal scale, and socio-economic conditions influence the intervention cost and cost distribution. In chapter four, I employ a trait-based approach to produce a framework for developing indices of species vulnerability to macroplastic pollution. Finally, in chapter five, I implement the framework developed in the previous chapter and present a multi-taxonomic, macroplastic vulnerability index for three marine taxa—mammals, birds, and turtles—to identify the marine species most vulnerable to macroplastic pollution in Hawai‘i. Overall, my dissertation shows how policy-driven, systemic research of MPP and its interventions can improve efforts to address MPP and its socio-economic and ecological consequences.