Physiological effects of tourism and associated food provisioning in an endangered iguana

A meta-analysis of human disturbance effects on glucocorticoid hormones in free-ranging wild vertebrates

Free-ranging wild vertebrates need to cope with natural and anthropogenic stressors that cause short and/or long-term behavioural and physiological responses. In areas of high human disturbance, the use of glucocorticoid (GC) hormones as biomarkers to measure stress responses is an increasingly common tool for understanding how animals cope with human disturbance. We conducted a meta-analysis to investigate how human disturbances such as habitat conversion, habitat degradation, and ecotourism influence baseline GC hormones of free-ranging wild vertebrates, and we further test the role of protected areas in reducing the impact of such disturbances on these hormones. A total of 58 studies met the inclusion criteria, providing 152 data points for comparing levels of GC hormones under disturbed and undisturbed conditions. The overall effect size suggests that human disturbance does not cause a consistent increase in levels of GC hormones (Hedges' g = 0.307, 95% CI = -0.062 to 0.677). However, when the data were analysed by disturbance type, living in unprotected areas or in areas with habitat conversion were found to increase GC hormone levels compared to living in protected or undisturbed areas. By contrast, we found no evidence that ecotourism or habitat degradation generates a consistent increase in baseline GC hormone levels. Among taxonomic groups, mammals appeared more sensitive to human disturbance than birds. We advocate the use of GC hormones for inferring major human-caused contributors to the stress levels of free-ranging wild vertebrates - although such information needs to be combined with other measures of stress and interpreted in the context of an organism's life history, behaviour, and history of interactions with human disturbance.

Meta-analysis reveals impacts of disturbance on reptile and amphibian body condition

Ecosystem disturbance is increasing in extent, severity and frequency across the globe. To date, research has largely focussed on the impacts of disturbance on animal population size, extinction risk and species richness. However, individual responses, such as changes in body condition, can act as more sensitive metrics and may provide early warning signs of reduced fitness and population declines. We conducted the first global systematic review and meta-analysis investigating the impacts of ecosystem disturbance on reptile and amphibian body condition. We collated 384 effect sizes representing 137 species from 133 studies. We tested how disturbance type, species traits, biome and taxon moderate the impacts of disturbance on body condition. We found an overall negative effect of disturbance on herpetofauna body condition (Hedges' g = -0.37, 95% CI: -0.57, -0.18). Disturbance type was an influential predictor of body condition response and all disturbance types had a negative mean effect. Drought, invasive species and agriculture had the largest effects. The impact of disturbance varied in strength and direction across biomes, with the largest negative effects found within Mediterranean and temperate biomes. In contrast, taxon, body size, habitat specialisation and conservation status were not influential predictors of disturbance effects. Our findings reveal the widespread effects of disturbance on herpetofauna body condition and highlight the potential role of individual-level response metrics in enhancing wildlife monitoring. The use of individual response metrics alongside population and community metrics would deepen our understanding of disturbance impacts by revealing both early impacts and chronic effects within affected populations. This could enable early and more informed conservation management.

Human-influenced diets affect the gut microbiome of wild baboons

Industrialized diets that incorporate processed foods and are often high in simple sugars and fats and low in fiber have myriad health impacts, many of which may operate via impacts on the gut microbiota. Examining how these diets affect the gut microbiota can be challenging given that lab animal models experience altered environmental contexts, and human studies include a suite of co-varying cultural and environmental factors that are likely to shape the gut microbiota alongside diet. To complement these approaches, we compare the microbiomes of wild populations of olive baboons (Papio anubis) with differential access to human trash high in processed foods, simple sugars, and fats in Rwanda's Akagera National Park. Baboons are a good model system since their microbiomes are compositionally similar to those of humans. Additionally, this population inhabits a common environment with different social groups consuming qualitatively different amounts of human trash, limiting variation in non-dietary factors. Using 16S rRNA gene amplicon sequencing we find that baboons with unlimited access to human trash have reduced microbial alpha diversity and reduced relative abundances of fiber-degrading taxa such as Ruminococcaceae, Prevotellaceae, and Lachnospiraceae. In contrast, baboons with limited access to human trash have a microbiome more similar to that of baboons with no access to human trash. Our results suggest that while a human-influenced diet high in processed foods, simple sugars, and fats is sufficient to alter the microbiome in wild baboons, there is a minimum threshold of dietary alteration that must occur before the microbiome is substantially altered. We recommend that data from wild primate populations such as these be used to complement ongoing research on diet-microbiome-health interactions in humans and lab animal models.

Integrative assessment of immunity, health-state, growth and survival of Magellanic penguin chicks in a colony exposed to ecotourism

Accumulating reports of negative impacts of tourist activities on wildlife emphasize the importance of closely monitoring focal populations. Although some effects are readily noticed, more subtle ones such as changes in physiological functions of individuals might go overlooked. Based on evidence of altered physiology associated with ecotourism on Magellanic penguins Spheniscus magellanicus, here we performed an integrated assessment using a diverse physiological toolkit together with more traditional fitness-related measures to better understand mechanisms and potential consequences. Chicks exposed to tourism showed altered immune parameters and elevated flea prevalence, reinforcing previous findings. Tourism-exposed female, but not male, chicks also showed relatively lower hematocrit and plasma protein levels, providing evidence consistent with a sex-specific response to tourist visitation. Physiological alterations detected in tourism-exposed young chicks (week 1-2) were maintained and the effect on flea infestation increased during the study period (week 4-5 of post-hatch). Despite the effects on physiology, these did not seem to translate into immediate fitness costs. No detectable tourism effects were found on brood sex ratios, chick growth and body condition, and survival until week 5-6 post-hatch. We detected no effects on reproductive output and only a marginal effect on nest survival during incubation despite previous reports of tourism-associated alterations in stress indices of adults. This disconnection could result if the physiological changes are not strong enough to impact fitness, if effects balance each other out, or if changes are part of a copying strategy. Alternatively, the physiological alterations might only show impacts later in the brooding cycle or even after chick emancipation from their parents. Our results suggest that integrative monitoring of potential anthropogenic impacts on wildlife should include evaluation of physiological mechanisms and individual-level responses in populations exposed to human activities.

Blood chemistry and biliverdin differ according to reproduction and tourism in a free-living lizard

Changes in the physiological health of species are an essential indicator of changing conditions and environmental challenges. Reponses to environmental challenges can often induce stress, influence physiology, and change metabolism in organisms. Here we tested blood chemistry parameters indicative of stress and metabolic activity using an i-STAT point-of-care blood analyzer in seven populations of free-ranging rock iguanas exposed to varying levels of tourism and supplemental feeding. We found significant differences in blood chemistry (glucose, oxygen, carbon dioxide, hematocrit, hemoglobin, calcium, potassium, and biliverdin levels) among populations exposed to varying levels of tourism, and some variation between sexes and reproductive states. However, different variables are not directly related to one another, suggesting that the causal physiological pathways driving tourism-induced differences are influenced by mechanisms that are not detected by common analyses of blood chemistry. Future work should investigate upstream regulators of these factors affected by tourism. Regardless, these blood metrics are known to be both stress sensitive and related to metabolic activity, suggesting that exposure to tourism and associated supplemental feeding by tourists are generally driven by stress-related changes in blood chemistry, biliverdin, and metabolism.

The predicted impact of resource provisioning on the epidemiological responses of different parasites

Anthropogenic activities and natural events such as periodic tree masting can alter resource provisioning in the environment, directly affecting animals, and potentially impacting the spread of infectious diseases in wildlife. The impact of these additional resources on infectious diseases can manifest through different pathways, affecting host susceptibility, contact rate and host demography. To date however, empirical research has tended to examine these different pathways in isolation, for example by quantifying the effects of provisioning on host behaviour in the wild or changes in immune responses in controlled laboratory studies. Furthermore, while theory has investigated the interactions between these pathways, this work has focussed on a narrow subset of pathogen types, typically directly transmitted microparasites. Given the diverse ways that provisioning can affect host susceptibility, contact patterns or host demography, we may expect the epidemiological consequences of provisioning to vary among different parasite types, dependent on key aspects of parasite life history, such as the duration of infection and transmission mode. Focusing on an exemplar empirical system, the wood mouse Apodemus sylvaticus, and its diverse parasite community, we developed a suite of epidemiological models to compare how resource provisioning alters responses for a range of these parasites that vary in their biology (microparasite and macroparasite), transmission mode (direct, environmental and vector transmitted) and duration of infection (acute, latent and chronic) within the same host population. We show there are common epidemiological responses to host resource provisioning across all parasite types examined. In particular, the epidemiological impact of provisioning could be driven in opposite directions, depending on which host pathways (contact rate, susceptibility or host demography) are most altered by the addition of resources to the environment. Broadly, these responses were qualitatively consistent across all parasite types, emphasising the importance of identifying general trade-offs between provisioning-altered parameters. Despite the qualitative consistency in responses to provisioning across parasite types, we predicted notable quantitative differences between parasites, with directly transmitted parasites (those conforming to SIR and SIS frameworks) predicted to show the strongest responses to provisioning among those examined, whereas the vector-borne parasites showed negligible responses to provisioning. As such, these analyses suggest that different parasites may show different scales of response to the same provisioning scenario, even within the same host population. This highlights the importance of knowing key aspects of host-parasite biology, to understand and predict epidemiological responses to provisioning for any specific host-parasite system.

Glucose tolerance of iguanas is affected by high-sugar diets in the lab and supplemental feeding by ecotourists in the wild

There is great interspecific variation in the nutritional composition of natural diets, and the varied nutritional content is physiologically tolerated because of evolutionarily based balances between diet composition and processing ability. However, as a result of landscape change and human exposure, unnatural diets are becoming widespread among wildlife without the necessary time for evolutionary matching between the diet and its processing. We tested how a controlled, unnatural high glucose diet affects glucose tolerance using captive green iguanas, and we performed similar glucose tolerance tests on wild Northern Bahamian rock iguanas that are either frequently fed grapes by tourists or experience no such supplementation. We evaluated both short and longer-term blood glucose responses and corticosterone (CORT) concentrations as changes have been associated with altered diets. Experimental glucose supplementation in the laboratory and tourist feeding in the wild both significantly affected glucose metabolism. When iguanas received a glucose-rich diet, we found greater acute increases in blood glucose following a glucose challenge. Relative to unfed iguanas, tourist-fed iguanas had significantly lower baseline CORT, higher baseline blood glucose, and slower returns to baseline glucose levels following a glucose challenge. Therefore, unnatural consumption of high amounts of glucose alters glucose metabolism in laboratory iguanas with short-term glucose treatment and free-living iguanas exposed to long-term feeding by tourists. Based on these results and the increasing prevalence of anthropogenically altered wildlife diets, the consequences of dietary changes on glucose metabolism should be further investigated across species, as such changes in glucose metabolism have health consequences in humans (e.g. diabetes).

Complex tourism and season interactions contribute to disparate physiologies in an endangered rock iguana

To promote survival and fitness, organisms use a suite of physiological systems to respond to both predictable and unpredictable changes in the environment. These physiological responses are also influenced by changes in life history state. The continued activation of physiological systems stemming from persistent environmental perturbations enable animals to cope with these challenges but may over time lead to significant effects on the health of wildlife. In the present study, we tested how varying environmental perturbations driven by tourism and associated supplemental feeding affects the energetics, corticosterone and immunity of six discrete populations of the northern Bahamian rock iguana (Cyclura cychlura inornata and Cyclura cychlura figginsi). We studied populations within and outside the reproductive season and quantified tourist numbers during sample collection. Specifically, we measured clutch size, body condition, plasma energy metabolites, reactive oxygen species, baseline corticosterone concentrations and immune function of male and female iguanas from each population to address whether (i) disparate physiologies are emerging across a gradient of tourism and feeding, (ii) both subspecies respond similarly and (iii) responses vary with season/reproductive condition. We found significant effects of tourism level, season and their interaction on the physiology of both C. c. inornata and C. c. figginsi, supporting the idea that tourism is leading to the divergence of phenotypes. Specifically, we found elevated plasma energy metabolites, oxidative stress and a measure of innate immunity (bactericidal ability), but reduced corticosterone concentrations with increasing tourism in both subspecies of rock iguanas. These physiological metrics differ according to the level of tourism in both subspecies and persist across seasons despite variation with natural seasonal and reproductive changes. These findings suggest that anthropogenic disturbance results in disparate physiologies in northern Bahamian rock iguanas.

Maternal effects in mammals: Broadening our understanding of offspring programming

The perinatal period is a sensitive time in mammalian development that can have long-lasting consequences on offspring phenotype via maternal effects. Maternal effects have been most intensively studied with respect to two major conditions: maternal diet and maternal stress. In this review, we shift the focus by discussing five major additional maternal cues and their influence on offspring phenotype: maternal androgen levels, photoperiod (melatonin), microbiome, immune regulation, and milk composition. We present the key findings for each of these topics in mammals, their mechanisms of action, and how they interact with each other and with the maternal influences of diet and stress. We explore their impacts in the contexts of both predictive adaptive responses and the developmental origins of disease, identify knowledge gaps and research opportunities in the field, and place a particular emphasis on the application and consideration of these effects in non-model species and natural ecological systems.

The elephant at the fence: almsman, panhandler, friend or foe?

Feeding of wild Asian elephants at the Udawalawe National Park perimeter electric fence by the general public is longstanding. We monitored the elephants and feeding activities, and conducted questionnaire surveys of stakeholders. Over 50 individual adult male elephants engaged in the activity. The exclusive male presence was consistent with a high-risk high-gain male strategy. The elephants were mostly offered fruits and vegetables. Over a thousand people a day watched and fed the elephants. Most people bought food for elephants from roadside stalls and vendors had significantly more sales if elephants were present. The feeding of elephants brought significant economic benefit to communities bordering the park. We found the impacts of feeding on the elephants and environment to be largely neutral. Impacts on people and conservation were mainly positive. Actions taken by authorities to stop the feeding have targeted the elephants and resulted in the decrease of feeding but not its elimination. Managing the activity instead would help increase economic benefits and ensure safe interaction between people and elephants. Such management, by directly benefitting local communities, could make them partners in the conservation process and form the basis of an effective outreach program.

Stoichiometric and stable isotope ratios of wild lizards in an urban landscape vary with reproduction, physiology, space and time

Spatial and temporal variation in stoichiometric and stable isotope ratios of animals contains ecological information that we are just beginning to understand. In both field and lab studies, stoichiometric or isotopic ratios are related to physiological mechanisms underlying nutrition or stress. Conservation and ecosystem ecology may be informed by isotopic data that can be rapidly and non-lethally collected from wild animals, especially where human activity leaves an isotopic signature (e.g. via introduction of chemical fertilizers, ornamental or other non-native plants or organic detritus). We examined spatial and temporal variation in stoichiometric and stable isotope ratios of the toes of Uta stansburiana (side-blotched lizards) living in urban and rural areas in and around St. George, Utah. We found substantial spatial and temporal variation as well as context-dependent co-variation with reproductive physiological parameters, although certain key predictions such as the relationship between δ¹⁵N and body condition were not supported. We suggest that landscape change through urbanization can have profound effects on wild animal physiology and that stoichiometric and stable isotope ratios can provide unique insights into the mechanisms underlying these processes.

Gut Microbiota of Wild and Captive Alpine Musk Deer (Moschus chrysogaster)

As for the wild animals, their diet components are always changed, so that we have to monitor such changes by analyzing the modification of intestinal microbial community. Such effort allows us to amend their conservation strategies and tactics accordingly so that they are able to appropriately adapt to the new environment and dietary selection. In this study we focus on the gut flora of two groups of an endangered species, Alpine musk deer (Moschus chrysogaster), wild group (WG) which is compared with that of the individuals of the same species but kept in the captivities (CG), a control group. Such a project is aimed to work out whether the composition of the gut microbes has significantly been changed due to captive feedings. To do so, we used 16S rRNA amplicon sequencing to characterize gut bacteria of the musk deer from the two groups. The results show that there is a significant difference in community structure of the bacteria: WG shows significant enrichment of Firmicutes and depletion of Bacteroidetes, while CG has a significant abundance of Proteobacteria and Euryarchaeota. Metagenomics was used to analyze the differences in functional enzymes between the two groups. The related results indicate that genes in WG are mostly related to the enzymes digesting cellulose and generating short-chain fatty acids (SCFAs) for signaling pathways, but CG shows enrichment in methanogenesis, including the CO₂/H₂ pathway and the methylotrophic pathway. Thus, this study indicates that the Firmicutes-rich gut microbiota in the WG enables individuals to maximize their energy intake from the cellulose, and has significant abundance of Euryarchaeota and methanogenesis pathways that allow them to reduce redundant energy consumption in methane metabolism, ensuring them to adapt to the wild environments.

Assessing the status of a threatened island endemic, Ctenosaura oedirhina, on Roatán, Honduras

Abstract Context Organisms living in small, isolated populations with very restricted ranges are at high risk of extirpation due to various direct and indirect forces than mainland populations. Roatán spiny-tailed iguanas (Ctenosaura oedirhina) are endemic to the 146-km2 island of Roatán, Honduras. Harvesting for consumption, fragmentation of habitat and predation by domestic animals threaten the existence of this lizard. This species is federally protected in Honduras; however, enforcement is rare. These iguanas are also listed as Endangered by the International Union for Conservation of Nature (IUCN) and are on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This species is geographically and genetically isolated into small subpopulations that are declining in density. Aims To estimate the population size of Roatán spiny-tailed iguanas (Ctenosaura oedirhina) on the island of Roatán, Honduras. Methods Distance sampling surveys have been used to monitor this species since 2012, and have been used to determine population density at five study sites. Estimates of density at those sites and across the island were used to calculate the population size of this species. Key results The present study elucidates that the high-density populations remaining are declining. The current population size is estimated to be 3759 (95% CI=1406–12616) individuals within the study sites, with 730 additional iguanas potentially outside of the study sites. Conclusions If the current level of decline continues, this species may become extirpated from some locations on Roatán, and go extinct in the wild. Although Honduras does have laws protecting this species and other wildlife, enforcement must be enhanced. Implications Lack of enforced protection for this species allows poaching for consumption to continue, which has been shown to alter its distribution and cause increased adult mortality. Local customs value the consumption of this species, creating a delicate management situation. Recommendations include strategies that mitigate the threat posed by consumption and increase enforcement of the current laws, while acknowledging cultural traditions.

Physiological stress responses of tigers due to anthropogenic disturbance especially tourism in two central Indian tiger reserves

Tigers continue to face unprecedented threats to their existence due to poaching, habitat loss, habitat fragmentation and anthropogenic disturbances. The present study examines the physiological stress response of tigers due to anthropogenic activities including wildlife tourism in Bandhavgarh Tiger Reserve and Kanha Tiger Reserve using faecal glucocorticoid metabolite (fGCM) measurement. We collected a total of 341 faecal samples from both reserves during tourism and non-tourism periods. Data on various anthropogenic disturbances including tourism activities like number of vehicles and visitors were also collected. We ascertained the species identity and sex of all the samples collected using genetic markers. fGCMs were extracted using a previously reported procedure, and fGCM concentrations were subsequently determined using an established enzyme immunoassay. There was no significant difference in overall mean fGCM concentrations between the two tiger reserves, but within each reserve, concentrations were significantly higher in tigers during the tourism period as compared to the non-tourism period. We also found that the number of tourist vehicles and disturbance level significantly correlated with fGCM concentrations. This study further supports the assumption that unbridled tourism associated with high anthropogenic disturbance can be related to perceived stress and consequently may have an impact on the reproductive fitness of tigers and long-term survival of isolated populations.

Associations among tourist camp management, high and low tourist seasons, and welfare factors in female Asian elephants in Thailand

This study investigated how camp management and tourist activities affect body condition, adrenocortical function, lipid profiles and metabolic status in female tourist elephants. We compared twice monthly serum insulin, glucose, fructosamine, total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL), high density lipoprotein (HDL), and fecal glucocorticoid metabolite (FGM) concentrations to body condition scores (BCS) at five camps with different management styles (e.g., tourist activities, work type, diet) between the High (November–February) and Low (March–October) tourist seasons. There were significant camp effects on health parameters, with BCS, TC, HDL, insulin and glucose being among the highest, and G:I being the lowest (less heathy) in elephants at an observation camp compared to those at camps where elephants received exercise by providing rides to tourists. Differences between High and Low tourist season months also were found for all measures, except TG and FGM concentrations. Both work time and walking distance were negatively correlated to glucose, fructosamine and insulin, while walking distance was negatively related to FGM concentrations. By contrast, positive associations were found between tourist number and BCS, TG, and insulin, perhaps related to tourists feeding elephants. Quantity of supplementary diet items (e.g., bananas, sugar cane, pumpkin) were positively correlated with FGM concentrations, glucose, fructosamine, and insulin. This study provides evidence that body condition, adrenal activity, metabolic markers, and lipid profiles in captive elephants may be affected by visitor numbers, work activities, and the amount of supplementary foods offered by tourists. Some activities appear to have negative (e.g., feeding), while others (e.g., exercise) may have positive effects on health and welfare. We conclude that camps adopting a more hands-off approach to tourism need to ensure elephants remain healthy by providing environments that encourage activity and rely on more natural diets or foraging.

Marine subsidies likely cause gigantism of iguanas in the Bahamas

We utilized natural experiment opportunities presented by differential conditions (presence/absence of seabirds and invasive species) on cays in the Bahamas to study whether interisland variations in food resources contributed to gigantism in Allen Cays Rock Iguanas (Cyclura cychlura inornata). We analyzed the stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values from iguana tissues and resources from each island food web to test the predictions that (1) food webs on islands with seabirds exhibit the influence of marine subsidies from seabird guano, whereas those from non-seabird islands do not, and (2) size differences in iguanas among cays were due to either (a) supplemental food availability from mice and/or seabird carcasses killed by barn owls (Tyto alba) and/or (b) access to more nutrient-rich vegetation fertilized by seabird guano. Food web components from the seabird island (Allen Cay) had 5-9‰ higher δ¹⁵N values than those on the other cays and Allen Cay plants contained nearly two times more nitrogen. Bayesian stable isotope mixing models indicated that C₃ plants dominated iguana diets on all islands and showed no evidence for consumption of mice or shearwaters. The iguanas on Allen Cay were ~ 2 times longer (48.3 ± 11.6 cm) and ~ 6 times heavier (5499 ± 2847 g) than iguanas on other cays and this was likely from marine-derived subsidies from seabird guano which caused an increase in nitrogen concentration in the plants and a resultant increase in the δ¹⁵N values across the entire food web relative to non-seabird islands.

Host sex, size, and hemoparasite infection influence the effects of ectoparasitic burdens on free-ranging iguanas

Investigations focusing on host-ectoparasite interactions in animals have revealed asymptomatic to severe health and fitness consequences suggesting that species mobilize different interspecific response mechanisms. Fewer studies, however, have examined intraspecific responses to ectoparasitic burdens. In this study, we analyzed host health and fitness responses to increasing ectoparasite burdens along with the presence/absence of hemoparasites of free-ranging insular rock iguanas (Cyclura cychlura) in The Bahamas. Using hematology, plasma biochemistry, as well as body condition and growth rate comparisons, we failed to find significant associations of tick burdens with annual growth rate, corticosterone, packed cell volume, total white blood cell, and heterophil, monocyte, eosinophil or hemoglobin measures. We did, however, find mixed and significant associations of tick burdens with lymphocyte and basophil counts, heterophil-to-lymphocyte ratios, and body condition indices. These associations varied by sex, size, and hemoparasite infection status suggesting that different life stages of iguanas may invest differently in immune responses, and impacts may be modulated based on size and sex of hosts, and coinfection status.

From wetland specialist to hand-fed generalist: shifts in diet and condition with provisioning for a recently urbanized wading bird

Many wildlife species shift their diets to use novel resources in urban areas. The consequences of these shifts are not well known, and consumption of reliable-but low quality-anthropogenic food may present important trade-offs for wildlife health. This may be especially true for carnivorous species such as the American white ibis (Eudocimus albus), a nomadic wading bird which has been increasingly observed in urban parks in South Florida, USA. We tested the effects of anthropogenic provisioning on consumer nutrition (i.e. dietary protein), body condition and ectoparasite burdens along an urban gradient using stable isotope analysis, scaled mass index values and GPS transmitter data. Ibises that assimilated more provisioned food were captured at more urban sites, used more urban habitat, had lower mass-length residuals, lower ectoparasite scores, assimilated less δ15N and had smaller dietary isotopic ellipses. Our results suggest that ibises in urban areas are heavily provisioned with anthropogenic food, which appears to offer a trade-off by providing low-quality, but easily accessible, calories that may not support high mass but may increase time available for anti-parasite behaviours such as preening. Understanding such trade-offs is important for investigating the effects of provisioning on infection risk and the conservation of wildlife in human-modified habitats.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

The association between diet of periurban wild dogs and zoonotic pathogen carriage

Established wildlife populations in periurban environments provide an opportunity to spread zoonotic pathogens within human-associated environments. Characteristics of prevalent pathogens harboured by periurban wild dogs suggest that dietary preference could influence their infection status; however, data comparing diet composition and pathogen presence are rarely available. We analysed the stomach contents of 170 periurban wild dogs (Canis familiaris) for the occurrence and biomass of prey items, and then associated this with their known infection status of key zoonotic pathogens. The staple prey items detected were mammalian prey species, most commonly swamp wallabies (Wallabia bicolor) (20.6±6.1%), canines (C. familiaris) (prey) (10.6±4.6%), eastern grey kangaroos (Macropus giganteus) (10.0±4.5%), and deer (various species) (10.0±4.5%). Unidentified bird species (10.0±4.5%) were also common. Wild dogs that were positive for Echinococcus granulosus were significantly more likely to have consumed swamp wallabies. These findings demonstrate the importance of managing both the definitive and intermediate stages of E. granulosus, and suggest that diet correlates with pathogen presence in some cases. This information may assist the development of specific strategies to manage zoonotic pathogens of wild dogs, which are currently lacking.

Ecotourism effects on health and immunity of Magellanic penguins at two reproductive colonies with disparate touristic regimes and population trends

Negative effects of ecotourism on wildlife are rising worldwide. Conservation physiology can play a major role in protecting wildlife by providing early alerts on changes in the status of individuals exposed to tourist activities. We measured an integrated set of immune and health-state indices to evaluate the effects of ecotourism on Magellanic penguins (Spheniscus magellanicus). We studied two reproductive colonies that differed in the intensity of tourism and population trends: Punta Tombo (higher tourism intensity, declining population) and San Lorenzo (lower tourism intensity, growing population). Within each colony, we compared individuals from an area that was exposed to tourists and a control area where tourism was excluded. Adult penguins exposed to tourism at Punta Tombo, but not at San Lorenzo, showed physiological alterations indicative of chronic stress (higher heterophil to lymphocyte ratios) and parasitic infection (elevated heterophil and eosinophil counts). Penguin chicks exposed to tourism at Punta Tombo, but not at San Lorenzo, also showed physiological alterations indicative of poor immune and general-health condition: lower humoral innate immunity, haematocrit, and glucose levels and higher inflammatory responses likely due to increased prevalence of fleas. Our results indicate that individuals of a declining population exposed to high levels of tourism express physiological indicators of chronic stress and poor health that could make adults and juveniles vulnerable to disease. These effects are expressed despite a long history of exposure and behavioural habituation to human visitation. In contrast, individuals of a growing population exposed to more recent and lower levels of tourism showed no effect. Our study demonstrates how a diverse physiological toolkit within a conservation physiology approach can provide important information for a better comprehension of anthropogenic effects on wild animals in our changing world.

Using host species traits to understand the consequences of resource provisioning for host-parasite interactions

Supplemental food provided to wildlife by human activities can be more abundant and predictable than natural resources, and subsequent changes in wildlife ecology can have profound impacts on host-parasite interactions. Identifying traits of species associated with increases or decreases in infection outcomes with resource provisioning could improve assessments of wildlife most prone to disease risks in changing environments. We conducted a phylogenetic meta-analysis of 342 host-parasite interactions across 56 wildlife species and three broad taxonomic groups of parasites to identify host-level traits that influence whether provisioning is associated with increases or decreases in infection. We predicted dietary generalists that capitalize on novel food would show greater infection in provisioned habitats owing to population growth and food-borne exposure to contaminants and parasite infectious stages. Similarly, species with fast life histories could experience stronger demographic and immunological benefits from provisioning that affect parasite transmission. We also predicted that wide-ranging and migratory behaviours could increase infection risks with provisioning if concentrated and non-seasonal foods promote dense aggregations that increase exposure to parasites. We found that provisioning increased infection with bacteria, viruses, fungi and protozoa (i.e. microparasites) most for wide-ranging, dietary generalist host species. Effect sizes for ectoparasites were also highest for host species with large home ranges but were instead lowest for dietary generalists. In contrast, the type of provisioning was a stronger correlate of infection outcomes for helminths than host species traits. Our analysis highlights host traits related to movement and feeding behaviour as important determinants of whether species experience greater infection with supplemental feeding. These results could help prioritize monitoring wildlife with particular trait profiles in anthropogenic habitats to reduce infectious disease risks in provisioned populations.

Nutritional physiology and ecology of wildlife in a changing world

Over the last century, humans have modified landscapes, generated pollution and provided opportunities for exotic species to invade areas where they did not evolve. In addition, humans now interact with animals in a growing number of ways (e.g. ecotourism). As a result, the quality (i.e. nutrient composition) and quantity (i.e. food abundance) of dietary items consumed by wildlife have, in many cases, changed. We present representative examples of the extent to which vertebrate foraging behaviour, food availability (quantity and quality) and digestive physiology have been modified due to human-induced environmental changes and human activities. We find that these effects can be quite extensive, especially as a result of pollution and human-provisioned food sources (despite good intentions). We also discuss the role of nutrition in conservation practices, from the perspective of both in situ and ex situ conservation. Though we find that the changes in the nutritional ecology and physiology of wildlife due to human alterations are typically negative and largely involve impacts on foraging behaviour and food availability, the extent to which these will affect the fitness of organisms and result in evolutionary changes is not clearly understood, and requires further investigation.

Assessing the Effects of Tourist Provisioning on the Health of Wild Barbary Macaques in Morocco

Feeding wildlife is a very popular tourist activity, largely because it facilitates the close observation of animals in their natural habitat. Such provisioning may benefit animals by improving their survival and reproductive success, especially during periods of natural food shortage. However, provisioning by tourists may also have negative impacts on the health of the animals involved; to date such impacts are poorly understood. Here, we investigated the effects of tourist provisioning on the health of wild adult Barbary macaques, Macaca sylvanus, in Morocco. We compared health measures between a heavily provisioned group and a group that received negligible food from tourists and, in the former group, we also assessed health measures in relation to the intensity of provisioning. We used a broad range of non-invasive health measures relating to birth rate and survival, disease and injury risk, body size and condition, and physiological stress. Our findings indicate that feeding by tourists may overall have negative impacts on the health of Barbary macaques, being linked in particular to larger body size, elevated stress levels and more alopecia. Finally, we propose a framework to help consider the potential costs and benefits of provisioning, which may facilitate future research and management decisions on whether-and how much-provisioning is acceptable.

Genetic diversity and structure in the Endangered Allen Cays Rock Iguana, Cyclura cychlura inornata

The Endangered Allen Cays Rock Iguana (Cyclura cychlura inornata) is endemic to the Allen Cays, a tiny cluster of islands in the Bahamas. Naturally occurring populations exist on only two cays (<4 ha each). However, populations of unknown origin were recently discovered on four additional cays. To investigate patterns of genetic variation among these populations, we analyzed nuclear and mitochondrial markers for 268 individuals. Analysis of three mitochondrial gene regions (2,328 bp) and data for eight nuclear microsatellite loci indicated low genetic diversity overall. Estimates of effective population sizes based on multilocus genotypes were also extremely low. Despite low diversity, significant population structuring and variation in genetic diversity measures were detected among cays. Genetic data confirm the source population for an experimentally translocated population while raising concerns regarding other, unauthorized, translocations. Reduced heterozygosity is consistent with a documented historical population decline due to overharvest. This study provides the first range-wide genetic analysis of this subspecies. We suggest strategies to maximize genetic diversity during ongoing recovery including additional translocations to establish assurance populations and additional protective measures for the two remaining natural populations.

Glucocorticoid Stress Responses of Reintroduced Tigers in Relation to Anthropogenic Disturbance in Sariska Tiger Reserve in India

Tiger (Panthera tigris), an endangered species, is under severe threat from poaching, habitat loss, prey depletion and habitat disturbance. Such factors have been reported causing local extermination of tiger populations including in one of the most important reserves in India, namely Sariska Tiger Reserve (STR) in northwestern India. Consequently, tigers were reintroduced in STR between 2008 and 2010, but inadequate breeding success was observed over the years, thus invoking an investigation to ascertain physiological correlates. In the present study, we report glucocorticoid stress responses of the reintroduced tigers in relation to anthropogenic disturbance in the STR from 2011 to 2013. We found anthropogenic disturbance such as encounter rates of livestock and humans, distance to roads and efforts to kill domestic livestock associated with an elevation in fecal glucocorticoid metabolite (fGCM) concentrations in the monitored tigers. In this regard, female tigers seem more sensitive to such disturbance than males. It was possible to discern that tiger’s fGCM levels were significantly positively related to the time spent in disturbed areas. Resulting management recommendations include relocation of villages from core areas and restriction of all anthropogenic activities in the entire STR.

Linking anthropogenic resources to wildlife-pathogen dynamics: a review and meta-analysis

Urbanisation and agriculture cause declines for many wildlife, but some species benefit from novel resources, especially food, provided in human-dominated habitats. Resulting shifts in wildlife ecology can alter infectious disease dynamics and create opportunities for cross-species transmission, yet predicting host-pathogen responses to resource provisioning is challenging. Factors enhancing transmission, such as increased aggregation, could be offset by better host immunity due to improved nutrition. Here, we conduct a review and meta-analysis to show that food provisioning results in highly heterogeneous infection outcomes that depend on pathogen type and anthropogenic food source. We also find empirical support for behavioural and immune mechanisms through which human-provided resources alter host exposure and tolerance to pathogens. A review of recent theoretical models of resource provisioning and infection dynamics shows that changes in host contact rates and immunity produce strong non-linear responses in pathogen invasion and prevalence. By integrating results of our meta-analysis back into a theoretical framework, we find provisioning amplifies pathogen invasion under increased host aggregation and tolerance, but reduces transmission if provisioned food decreases dietary exposure to parasites. These results carry implications for wildlife disease management and highlight areas for future work, such as how resource shifts might affect virulence evolution.

A conceptual framework for the emerging discipline of conservation physiology

Current rates of biodiversity decline are unprecedented and largely attributed to anthropogenic influences. Given the scope and magnitude of conservation issues, policy and management interventions must maximize efficiency and efficacy. The relatively new field of conservation physiology reveals the physiological mechanisms associated with population declines, animal-environment relationships and population or species tolerance thresholds, particularly where these relate to anthropogenic factors that necessitate conservation action. We propose a framework that demonstrates an integrative approach between physiology, conservation and policy, where each can inform the design, conduct and implementation of the other. Each junction of the conservation physiology process has the capacity to foster dialogue that contributes to effective implementation, monitoring, assessment and evaluation. This approach enables effective evaluation and implementation of evidence-based conservation policy and management decisions through a process of ongoing refinement, but may require that scientists (from the disciplines of both physiology and conservation) and policy-makers bridge interdisciplinary knowledge gaps. Here, we outline a conceptual framework that can guide and lead developments in conservation physiology, as well as promote innovative research that fosters conservation-motivated policy.

Biomarkers of oxidative status: missing tools in conservation physiology

Recent ecological studies have shown that oxidative status could have a significant impact on fitness components in wild animals. Not only can oxidative status reflect the environmental conditions that animals experience, but it can also predict their chances of reproduction and survival in the future in their natural habitat. Such important characteristics make markers of oxidative status informative tools to evaluate a priori individual perspectives of reproduction and survival as well as to assess a posteriori the effect of human activities on the fitness of species of conservation concern and wildlife in general. Markers of oxidative status may therefore help conservation practitioners to identify conservation threats to animal populations and to maximize the success of wildlife management. Despite these potential benefits for animal conservation programmes, up to now markers of oxidative status have only been reported anecdotally in conservation studies. The aim of this review is therefore to raise awareness by conservation practitioners of the use of markers of oxidative status. Towards this end, we first describe how environmental disruptions due to human activities can translate into variation in oxidative status. Second, we show how individual and population variation in oxidative status may contribute to the success or the failure of reintroduction or translocation programmes. Finally, we emphasize the technical features specific to the measurement of markers of oxidative status in conservation programmes, which may help investigators with the interpretation of their results. Such prior knowledge about markers of oxidative status may encourage conservation physiologists to use them in order to enhance the success of conservation programmes and wildlife management.