by We probed the effects of season, tourist exposure, and site on body condition (residuals of regression of body mass against SVL). local (e.g., tourism, pollution, habitat modification) to global (e.g., climate change) scales (Acevedo-Whitehouse and Duffus, 2009). Many of these changes have the capacity to impact the long-term persistence of natural populations. Chloroprocaine HCl However, the impact of human disturbances on individual physiological responses and the resulting effects on long-term health, survival, and fitness of a species remains largely unexamined (Wikelski and Cooke, 2006). Understanding such effects is usually a critical component for effectively assessing a populations risk of decline. Recent studies demonstrate that physiological responses to tourism are pronounced in a number of species (Ellenberg et al., 2007;Romero and Wikelski, 2002;Walker et al., 2005), but it is usually unclear what effects these responses have on health and survival in natural populations. The direction and temporal nature of the response also varies depending on the species, age class, or even populace (Mullner et al., 2004;Walker et al., 2005;Walker et al., 2006). While the vertebrate stress response is usually a key physiological response allowing organisms to cope with environmental change (Wingfield et al., 1998), there is no consensus as to the direction of the response or the downstream effects of an altered stress response in natural populations. Further, circulating glucocorticoid concentrations and stress responses are not static and instead vary according to period of the stressor, sex, season, reproductive state, and body condition making interpretation of glucocorticoid results complicated (Breuner et al., 1999;Ilmonen et al., 2003;Moore and Jessop, 2003;Romero, 2002). These context-dependent modifications of the stress response in populations constantly exposed to human disturbances likely have subsequent physiological and behavioral effects. Therefore, to fully understand the consequences of human-induced alterations of endocrine responses on an individual, it is important to concomitantly measure related and relevant physiological systems, such as the immune system, and to examine these responses under different individual and environmental contexts (e.g., season, reproductive state, sex). Investigating immune system function of individuals within given populations Chloroprocaine HCl is usually highly relevant to understanding the dynamics of the population in question, especially considering the introduction of novel pathogens in many areas including the Galapagos (Dobson and Foufopoulos, 2001;Harvell et al., 2002;Wikelski et al., 2004). Additionally, connections between stress, glucocorticoids, and immunity are well established; glucocorticoid receptors are present on lymphatic tissues and leukocytes throughout the body, and stress induces modifications of the immune system (Cidlowski et al., 1996;Leonard and Song, 2002;Weyts et al., 1998;Wiegers et Chloroprocaine HCl al., 1993). The specific relationships between stress and immunity, however, vary considerably with context. For example, a large number of studies have exhibited immunosuppression under chronic stress conditions, while others have reported that acute stress can actually enhance immune responses (Dhabhar, 1998;Dhabhar, Mouse monoclonal to ABCG2 2000;Dhabhar and McEwen, 1997). Thus, the notion of stress-induced immunosuppression is usually overly simplistic and the exact effects vary extensively depending on the type of stressor, the period of the stress, the specific immune response measured, and the dynamic and/or reproductive condition of the individuals (Dhabhar, 2000;Dhabhar and McEwen, 1997;French and Moore, 2008). The current study investigated the impact of ecotourism, a seemingly low-level human disturbance, on stress responsiveness and specific fitness-related immune steps in the Galapagos marine iguana (Amblyrhynchus cristatus). Marine iguanas are an ideal model to examine anthropogenic change because the geography provides adjacent iguana populations which have varying levels of human disturbance. Tourist sites are regularly visited by hundreds of people daily; in contrast non-tourist sites are highly protected Federal Reserve lands that are rarely frequented by people. Tourist and non-tourist iguana populations of similar size, density, and composition can be located along the same coastline less than a kilometer from each other. Previously, Romero and Wikelski investigated the effects of tourism on stress responsiveness of marine iguanas under extreme environmental conditions of increased water Chloroprocaine HCl temperatures and low food availability (El Nio); however, it is unfamiliar how individuals are affected by eco-tourism under non-extreme conditions (Romero and Wikelski, 2002). More importantly, it is unclear what these endocrine changes mean for individual health and survival. In the current study we tested whether human disturbance results in modifications to immune responses critical to health in marine iguanas and whether these modifications were related to baseline or stress-induced levels of plasma corticosterone..
