fGCM Concentrations Research Articles

Developing welfare parameters for African elephants (Loxodonta africana) in fenced reserves in South Africa.

South Africa has many fenced reserves harbouring small to medium sized populations of African elephant (Loxodonta africana), most of which have been translocated. Elephants on fenced reserves may be exposed to various management interventions and practices (translocation, hunting, darting, high tourism impact, contraception programs, disruption due to infrastructure maintenance, etc.). These factors may impact the welfare of elephants. Poor elephant welfare may have serious consequences such as increased inter- and intra-species aggression that could result in fatalities. This is the first study to attempt to define behavioural and physiological welfare parameters for free-ranging elephants on small to medium sized reserves. The eight study sites incorporated reserves with different social structure combinations, elephant life-histories, reserve sizes, habitat, management, and tourism intensity. Data collection consisted of behavioural observations (10-minute videos) as well as faecal samples. By incorporating both behavioural and physiological (faecal glucocorticoid metabolite (fGCM) concentration) parameters, we aimed to investigate whether the two parameters showed similar trends. Five behavioural categories were identified (Arousal, Assessing, Ambivalent, Ambivalent/ Body care, and Frustrated behaviour), with various detailed behaviours demonstrated by the elephants that may indicate the influence of anthropogenic disturbance and possibly impact on animal welfare. The study showed significant differences between the selected detailed behaviours, behavioural categories and fGCM concentrations of elephants across the eight reserves. History seemed to be a decisive factor, as reserves with predominantly ex-captive elephants showed higher frequencies of certain behaviours as well as higher fGCM concentrations. Age, sex, reserve size and season were also found to contribute to our defined welfare indices and fGCM concentrations. This indicates that behavioural parameters, indicative of certain behavioural states, are valuable indicators of welfare, as supported by the physiological response of the elephants. The results also highlight the importance of taking multiple specified behaviours from a category into consideration when evaluating the welfare of elephants, to account for individual variation.

Sex, not social behavior, predicts fecal glucocorticoid metabolite concentrations in a facultatively social rodent, the highland tuco-tuco (Ctenomys opimus)

Social relationships may influence circulating glucocorticoid levels, particularly in group-living species in which individuals regularly engage in interactions with conspecifics. The effects of such interactions appear to vary, with greater social contact being associated with increased glucocorticoid concentrations in some species but decreased concentrations in others. These distinct responses raise intriguing questions regarding relationships among social behavior, individual phenotypes, and glucocorticoid physiology. To explore such relationships in a free-living mammal with a dynamic social organization, we quantified variation in baseline glucocorticoids in a population of highland tuco-tucos (Ctenomys opimus) from Jujuy Province, Argentina. These subterranean rodents are facultatively social, with lone and group-living individuals regularly occurring within the same population. To assess potential endocrine correlates of this behavioral variability, we examined differences in baseline fecal glucocorticoid metabolite (fGCm) concentrations as a function of social group size and composition as well as several metrics of social behavior derived from social network analyses. Despite marked variability in social relationships among the 37 (12 male, 25 female) free-living tuco-tucos sampled, none of the measures of social behavior examined were significant predictors of variation in fGCm concentrations. In contrast, individual variation in glucocorticoid metabolites was best explained by sex, with males having higher fGCm concentrations than females. These analyses provide the first characterization of the glucocorticoid physiology of highland tuco-tucos and underscore the potential importance of intrinsic phenotypic factors (e.g., sex) in shaping glucocorticoid variation in free-living mammals.

Study of fecal glucocorticoid metabolites in captive Asian elephants in Kanchanaburi Province, Thailand.

Background and Aim:Over the past two decades, the number of elephant camps in Thailand has increased considerably, and captive elephants have become more popular within the tourism industry. Tourist activities involving elephant exhibitions and trekking potentially affect animal health and welfare. This study aimed to investigate the relationships between a novel stress biomarker, fecal glucocorticoid metabolites (fGCM), and various factors (sex, age, weather season, tourist season, and elephant usage patterns), monitoring the fGCM concentration during and after trekking activities ceased.Materials and Methods:Fecal samples of 20 captive Asian elephants from two camps in Kanchanaburi Province were collected monthly for 1 year. The fGCM concentrations were measured using enzyme immunoassay and evaluated relative to individual demography, season, and tourist trekking activity. The mean differences of fGCMs concentrations were compared by analysis of variance and t-test statistics according to data types with p<0.5.Results:Significant differences in mean fGCM concentrations were found between age categories (p=0.001), trekking and non-trekking animals (p=0.039), and during and after trekking (p=0.023). The mean fGCM concentration of elephants aged during 0-44 years (136.7 ng/g) was significantly higher than for animals over 44 years old (107.7 ng/g), and the elephant trekking group (144.9 ng/g) was significantly higher than the other group (124.7 ng/g). Within the trekking group, the mean fGCM concentrations gradually declined to 129.13 ng/g within 8 months of trekking cessation.Conclusion:Elephant’s ages and activities co-influenced the variance of fGCM concentrations. In addition, permanent tourist activity, especially trekking, can increase elephant stress. This study’s findings can be applied to the health status monitoring of captive elephants and result in improved animal welfare.

Spatial constraints and seasonal conditions but not poaching pressure are linked with elevated faecal glucocorticoid metabolite concentrations in white rhino

Context Due to considerable declines in African wildlife populations, most large African mammals are managed inside protected areas. Protected areas come in various sizes, and have different environmental features, climates and management strategies (i.e. ‘hands-on’ or ‘hands-off’) that can influence an animals’ homeostasis. White rhinos (Ceratotherium simum simum) are found almost exclusively within protected areas where population sizes are driven by natural factors and poaching pressures. Aims Our aim was to understand the effect of natural and anthropogenic factors on the adrenocortical response of white rhinos within three protected areas. Specifically, we wanted to understand how poaching pressure, protected area size (&lt;500 km2), season (wet and dry) and rainfall patterns were responsible for driving adrenocortical activity in white rhino. Methods To understand the relationship between rhino adrenocortical responses and different environmental and anthropogenic stressors, we quantified glucocorticoid metabolites in faecal samples (fGCM) collected from four populations within three protected areas (i.e. two small parks, one big park) during the wet and dry seasons. Key results We found differences in seasonal fGCM concentrations, with a 42% increase during the dry season, and no differences in fGCM concentrations between the high and low poaching areas. Additionally, we found fGCM concentrations in samples from the small parks were respectively 38% and 42% higher than in samples from the large park during both the dry and wet seasons compared. Conclusions Our results suggest that white rhinos may experience physiological stress in smaller parks, especially during the dry season when resources are limited. Implications By mitigating stress associated with reduced access to resources and spatial constraints, managers may better promote the viability of large mammals in small protected areas.

Cascading Effects of Hunting Disturbance on Northern Bobwhite Behavior, Physiology, and Survival

The northern bobwhite (Colinus virginianus; hereafter, bobwhite) is an important gamebird across the United States and has been in decline for several decades. As a commonly hunted prey species, the bobwhite provides an ideal study species to investigate the use of proactive and reactive antipredator behaviors in response to hunting pressure. We designed an experiment to understand how late-season hunting affects bobwhite demographics using fecal glucocorticoid (fGCM) concentrations, foraging and movement behaviors, survival, and breeding season metrics. Our results show that bobwhite responded to increased interactions with a shotgun through proactive responses. After one encounter with a discharged shotgun, bobwhite began foraging farther from supplemental feed where the risk of encountering a hunting party was the greatest (β = 0.21, 95% Bayesian credible interval [CrI]: 0.06–0.36). Bobwhite responded to increased hunting pressure, particularly late-season hunting pressure, via reactive responses through increased fecal glucocorticoid metabolite (fGCM) concentrations (β = 2.18, 95% CrI: 0.21–4.15), resulting in decreased survivorship in non-harvested individuals (β = -0.42, 95% CrI: -0.77 to -0.07) and decreased fecundity (β = -0.17, 95% CI: -0.31–0.09). These results can help inform hunting season regulations and management decisions aiding in bobwhite recovery.

A field-friendly alternative to freeze-drying faeces for glucocorticoid metabolite analyses of African wild dogs (Lycaon pictus)

Endocrine studies using faeces as hormone matrix have become increasingly popular to examine adrenocortical activity in wildlife. A prerequisite for this approach is to minimize alteration of faecal glucocorticoid metabolite (fGCM) composition post-defecation. This is done by freezing the collected material as soon as possible after collection, and removing moisture from the frozen faecal samples afterwards (usually by freeze-drying). In remote areas, freeze-drying opportunities are often limited, and in the case of the African wild dog (Lycaon pictus), established assays revealed that fGCM concentrations remain comparable for only ∼24h post-defaecation. In the present study, three cost-effective drying treatments (exposure to sunlight, placement in a solar oven, and use of a food dehydrator) were investigated as alternatives to the golden standard of freeze-drying faeces.•In comparison to freeze-dried material, African wild dog faecal samples dried through sunlight exposure, a solar oven, and use of a food dehydrator revealed no significant differences in respective fGCM concentrations measured.•A food dehydrator would be the preferable option to dry African wild dog faeces if limited electrical supply is available. This technique dries faeces the fastest, and negates any reliance on weather conditions.

Exploring seasonal variation in the faecal glucocorticoid concentrations of African elephants (

Context The wide-ranging movement of African elephants (Loxodonta africana) is largely driven by the spatio-temporal distribution of water and forage, and often leads to their travelling outside of formally protected areas. With an increase in drier periods predicted across Africa due to climate change, it is critically important to understand how elephants physiologically respond to alterations in the availability and distribution of resources. Aims We assessed variation in the adrenal activity of elephants living in Kenya’s Tsavo East National Park between wet and dry seasons, as well as among individuals found in Tsavo East National Park and privately protected Rukinga Wildlife Sanctuary (part of the Kasigau REDD+ wildlife corridor) in the dry season, when the area experiences an influx of elephants in search of alternative resources. Methods We opportunistically collected fresh elephant faecal samples across the two seasons and locations for analysis of faecal glucocorticoid metabolite (fGCM, a proxy for stress) and nitrogen (Nf, an indirect measure of diet quality) concentrations. The Normalised Difference Vegetation Index (NDVI) was employed as an additional indicator of habitat quality. Key results In Tsavo East N.P. Nf and NDVI were both significantly lower during the dry season, indicating poorer habitat quality compared with the wet season. Although elephant fGCM concentrations tended to be higher in the dry season than the wet, the differences were not significant. There was no difference between elephant fGCMs measured in Tsavo East N.P. and Rukinga W.S. during the dry season, nor in habitat quality between the two locations. Conclusions Elephants living in Tsavo may be physiologically unaffected by (or adapt to) typical seasonal changes in habitat quality that could lead to nutritional stress; however, whether this is the case during extended periods of severe drought requires further investigation. Rukinga W.S. provides a safe haven of sufficient habitat quality for elephants searching for alternative resources during this period. Implications Extended dry periods are likely to become increasingly common in semiarid savannahs, and implications for wildlife must be closely monitored. Privately protected land outside formally protected areas plays an important role in conservation efforts, which should be considered when making land management plans.

Loss of an apex predator in the wild induces physiological and behavioural changes in prey.

Predators can impact prey via predation or risk effects, which can initiate trophic cascades. Given widespread population declines of apex predators, understanding and predicting the associated ecological consequences is a priority. When predation risk is relatively unpredictable or uncontrollable by prey, the loss of predators is hypothesized to release prey from stress; however, there are few tests of this hypothesis in the wild. A well-studied predator-prey system between white sharks (Carcharodon carcharias) and Cape fur seals (Arctocephalus pusillus pusillus) in False Bay, South Africa, has previously demonstrated elevated faecal glucocorticoid metabolite concentrations (fGCMs) in seals exposed to high levels of predation risk from white sharks. A recent decline and disappearance of white sharks from the system has coincided with a pronounced decrease in seal fGCM concentrations. Seals have concurrently been rafting further from shore and over deeper water, a behaviour that would have previously rendered them vulnerable to attack. These results show rapid physiological and behavioural responses by seals to release from predation stress. To our knowledge, this represents the first demonstration in the wild of physiological changes in prey from predator decline, and such responses are likely to increase given the scale and pace of apex predator declines globally.

Quantification of faecal glucocorticoid metabolites as a measure of stress in the rock hyrax Procavia capensis living in an urban green space

Despite the abundance of rock hyrax Procavia capensis within South Africa's urban areas, there is not much information available about the effect of anthropogenic activities on rock hyrax wellbeing. To determine the potential impact of anthropogenic disturbance on adrenocortical activity, we conducted an ACTH challenge to identify a suitable enzyme‐immunoassay (EIA) for measuring faecal glucocorticoid metabolite (fGCM) concentrations in the rock hyrax. This study identified an 11β‐hydroxyaetiocholanolone EIA as the most suitable assay in this regard. The fGCM levels measured, indicate the physiological stress response in different rock hyrax populations, living in an area with varying degrees of anthropogenic activity (low, medium, high) within the National Botanical Garden of Pretoria, South Africa. The species' habituation to human numbers (weekly mean number of people) was examined by determining individual flight initiation distance (FID). Seasonally, there were overall higher fGCM concentrations in late spring compared to winter. The fGCM concentrations, although not significantly different but possibly biologically relevant, in the section with the lowest anthropogenic disturbance were ~10% higher compared to those in the section with medium disturbance, and ~20% higher compared to those in the section with the highest disturbance. Animal FID did not differ significantly between seasons but they did differ significantly between sections, and decreased in accordance with fGCM concentrations. The non‐invasive approach established in this study provides a foundation for assessing rock hyrax wellbeing, and can help better understand how anthropogenic presence is perceived as a stressor in this species.

Maternal stress effects on infant development in wild Verreaux's sifaka (Propithecus verreauxi)

Maternal effects mediated by nutrients or specific endocrine states of the mother can affect infant development. Specifically, pre- and postnatal maternal stress associated with elevated glucocorticoid (GC) output is known to influence the phenotype of the offspring, including their physical and behavioral development. These developmental processes, however, remain relatively poorly studied in wild vertebrates, including primates with their relatively slow life histories. Here, we investigated the effects of maternal stress, assessed by fecal glucocorticoid output, on infant development in wild Verreaux’s sifakas (Propithecus verreauxi), a group-living Malagasy primate. In a first step, we investigated factors predicting maternal fecal glucocorticoid metabolite (fGCM) concentrations, how they impact infants’ physical and behavioral development during the first 6 months of postnatal life as well as early survival during the first 1.5 years of postnatal life. We collected fecal samples of mothers for hormone assays and behavioral data of 12 infants from two birth cohorts, for which we also assessed growth rates. Maternal fGCM concentrations were higher during the late prenatal but lower during the postnatal period compared to the early/mid prenatal period and were higher during periods of low rainfall. Infants of mothers with higher prenatal fGCM concentrations exhibited faster growth rates and were more explorative in terms of independent foraging and play. Infants of mothers with high pre- and postnatal fGCM concentrations were carried less and spent more time in nipple contact. Time mothers spent carrying infants predicted infant survival: infants that were more carried had lower survival, suggesting that they were likely in poorer condition and had to be cared for longer. Thus, the physical and behavioral development of these young primates were impacted by variation in maternal fGCM concentrations during the first 6 months of their lives, presumably as an adaptive response to living in a highly seasonal, but unpredictable environment.Significance statementThe early development of infants can be impacted by variation in maternal condition. These maternal effects can be mediated by maternal stress (glucocorticoid hormones) and are known to have downstream consequences for behavior, physiology, survival, and reproductive success well into adulthood. However, the direction of the effects of maternal physiological GC output on offspring development is highly variable, even within the same species. We contribute comparative data on maternal stress effects on infant development in a Critically Endangered primate from Madagascar. We describe variation in maternal glucocorticoid output as a function of ecological and reproductive factors and show that patterns of infant growth, behavioral development, and early survival are predicted by maternal glucocorticoids. Our study demonstrates how mothers can influence offspring fitness in response to challenging environmental conditions.

Fecal glucocorticoid metabolites as an indicator of adrenocortical activity in Arctic foxes (Vulpes lagopus) and recommendations for future studies

Measuring fecal glucocorticoid metabolites (fGCMs) is a widely used, non-invasive method for studies of stress in vertebrates. To study physiological responses in wild Arctic foxes (Vulpes lagopus) to perceived stressors such as fluctuating food availability, occurrence of competitors and predators and disturbance from human activities, a species-specific physiological validation of a method to evaluate adrenocortical activity is needed. Here we used 15 captive Arctic foxes (both males and females and juveniles and adults) to investigate fGCM concentrations following ACTH injection (physiological validation), or handling alone and compared them with their respective baseline concentrations prior to the treatments. A 5α-pregnane-3ß,11ß,21-triol-20-one enzyme immunoassay measured significant fGCM increases following both treatments. The time lags to reach peak fGCM values were 9.3 ± 1.3 h and 12.8 ± 1.7 h for ACTH and handling treatment, respectively. Concentrations of fGCMs varied a lot between individuals, but not attributed to sex nor age of the foxes. However, we found a negative relationship between boldness and fGCM concentrations. Faecal glucocorticoid metabolites concentrations did not change significantly over a period of 48 h in samples kept at temperatures reflecting winter and summer means. This would allow the collection of samples up to two days old in the wild regardless of the season. We conclude that our successfully validated method for measuring fGCMs can be used as a non-invasive tool for studies exploring various stressors both in wild and captive Arctic foxes.

Behavioural change during dispersal and its relationship to survival and reproduction in a cooperative breeder.

The ability of dispersing individuals to adjust their behaviour to changing conditions is instrumental in overcoming challenges and reducing dispersal costs, consequently increasing overall dispersal success. Understanding how dispersers' behaviour and physiology change during the dispersal process, and how they differ from resident individuals, can shed light on the mechanisms by which dispersers increase survival and maximise reproduction.By analysing individual behaviour and concentrations of faecal glucocorticoid metabolites (fGCM), a stress‐associated biomarker, we sought to identify the proximate causes behind differences in survival and reproduction between dispersing and resident meerkats Suricata suricatta.We used data collected on 67 dispersing and 108 resident females to investigate (a) which individual, social and environmental factors are correlated to foraging and vigilance, and whether the role of such factors differs among dispersal phases, and between dispersers and residents; (b) how time allocated to either foraging or vigilance correlated to survival in dispersers and residents and (c) the link between aggression and change in fGCM concentration, and their relationship with reproductive rates in dispersing groups and resident groups with either long‐established or newly established dominant females.Time allocated to foraging increased across dispersal phases, whereas time allocated to vigilance decreased. Time allocated to foraging and vigilance correlated positively and negatively, respectively, with dispersers' group size. We did not find a group size effect for residents. High proportions of time allocated to foraging correlated with high survival, and more so in dispersers, suggesting that maintaining good physical condition may reduce mortality during dispersal. Furthermore, while subordinate individuals rarely reproduced in resident groups, the conception rate of subordinates in newly formed dispersing groups was equal to that of their dominant individuals. Mirroring conception rates, in resident groups, fGCM concentrations were lower in subordinates than in dominants, whereas in disperser groups, fGCM concentrations did not differ between subordinates and dominants.Our results, which highlight the relationship between behavioural and physiological factors and demographic rates, provide insights into some of the mechanisms that individuals of a cooperative species can use to increase overall dispersal success.

Repeatability of daily profiles of baseline glucocorticoid metabolites measured in the urine and faeces of eastern rock sengis (Elephantulus myurus)

Repeatability of hormone concentrations is of great interest for studies investigating the evolution of hormonal traits. Particularly the repeatability of glucocorticoids (GCs) in response to a stressor is frequently investigated, but often only point (initial and/or response value), or single measures are used. A new method takes into account the entire individual hormone profile and generates an individual profile repeatability (PR) score. The method was developed for response profiles, but it may also be valuable for baseline values in species with diurnal changes in hormone concentrations. GCs are determined in a variety of matrices, and repeatability can vary considerably depending on the matrix. We investigated the repeatability of baseline GC metabolite (GCM) concentrations measured in urine (uGCM) and faeces (fGCM) of captive eastern rock sengis (Elephantulus myurus) using the more traditional linear mixed model approach and the PR method. GCMs were assessed over 24 h and measurements were repeated twice with two weeks between replicates. A diurnal rhythm in GCM concentrations associated with the activity period of the sengis was found in urine, but not in the faeces. Urinary GCM concentrations exhibited a moderate repeatability, whereas the repeatability of fGCM concentrations was low. Urinary GCM concentrations and their repeatability differed between the sexes; with higher concentrations and lower PR scores in females. No such sex differences were apparent for fGCM concentrations and the PR score was not able to characterise repeatability of fGCM concentrations, which were lacking a distinct profile. The PR score enabled a successful quantification of the repeatability of the diurnal uGCM profiles. Hormone profile, sex and sample matrix can affect hormonal traits considerably and the results may be obscured if these factors are not carefully considered.

Measuring Faecal Glucocorticoid Metabolite Concentrations as an Indicator of Stress in Blue Wildebeest (Connochaetes taurinus)

In South Africa, blue wildebeest (Connochaetes taurinus) are routinely captured for relocation purposes. To monitor the stress caused by this practise, a non-invasive method assessing adrenocortical function as a measure of stress would minimize disturbance during sample collection. In our study, an adrenocorticotropic hormone challenge, and a mass-capture event were used to examine the suitability of five enzyme immunoassays (EIAs) for monitoring stress-related physiological responses using faeces as a sample matrix. The tested 11-oxoaetiocholanolone I EIA performed best, showing a 2126% increase above baseline after 22 h for a male, and a 474% increase for a female 23 h post-ACTH injection. Baseline faecal glucocorticoid metabolite (fGCM) concentrations did not differ between animals captured on either day 1 or day 2 of the capture event, indicating that the frequent presence of a helicopter during the two days did not influence fGCM concentrations. However, during capture-related restraint for up to 10 h, an overall 1.5-fold elevation in (fGCM) concentrations was found. Storage of faeces at ambient temperature post-defecation indicated a fair stability of fGCMs for up to 8 h. The ability to reliably assess adrenocortical function provides a solid basis to examine endocrine responses to putative stressful circumstances in blue wildebeest.

Hot and bothered: alterations in faecal glucocorticoid metabolite concentrations of the sungazer lizard, Smaug giganteus, in response to an increase in environmental temperature

Despite the commonly held belief that reptiles are immune to extreme temperatures, global warming is predicted to result in the loss of 40% of all reptile species by 2080. In order to understand the effects of elevated temperature on African reptile physiology and health, additional research is required. We studied the physiological stress response of sungazer lizards (Smaug giganteus) facing elevated temperatures within captivity. Control animals (1M, 2F) were kept at 30 °C throughout the 13-week study period. Test animals (1M, 2F) were exposed to 30 °C for four weeks (stage 1), 39 °C for six weeks (stage 2) and 30 °C for three weeks (stage 3). Faecal samples were collected from both control and test animals to monitor faecal glucocorticoid metabolite (fGCM) concentrations as a proxy of physiological stress. Although the fGCM levels of control females remained constant, test females showed an acute fGCM increase following the increase and subsequent decrease of temperatures. The test male had significantly higher fGCM levels during stage 3, compared with stage 1 and 2. The control male, although displaying constant fGCM levels throughout the study, had higher fGCM levels than the test male. The results indicate that a considerable temporal increase in environmental temperature did not lead to chronically elevated adrenocortical activity in sungazer lizards. It is likely that inherent traits within the species allow the species to adapt to such changes. Furthermore, the endangered status of the species and limited availability of study animals restricted the sample size in this study to a few, captive-based lizards. Therefore, although our results are an important addition to reptile conservation, they should be extrapolated to free-ranging populations with caution. Future research should consider the effects of chronically elevated temperature in relation to water and food shortages, as well as interindividual variation in physiological responses.

Experimental Manipulation of Air Temperature in Captivity Appears Unsuitable for Evaluating Fecal Glucocorticoid Metabolite Responses of Wild-Caught Birds to Heat Exposure.

AbstractNoninvasive measurement of stress-related alterations in fecal glucocorticoid metabolite (fGCM) concentrations has considerable potential for quantifying physiological responses to very hot weather in free-ranging birds, but practical considerations related to sampling will often make this method feasible only for habituated study populations. Here we evaluate an alternate approach, the use of experimentally manipulated thermal environments for evaluating stress responses to high environmental temperatures in wild-caught birds housed in captivity. Using an enzyme immunoassay utilizing antibodies against 5ß-pregnane-3α,11ß,21-triol-20-one-CMO∶BSA (tetrahydrocorticosterone), we quantified fGCMs in captive individuals of three southern African arid-zone species (southern pied babblers [Turdoides bicolor], white-browed sparrow-weavers [Plocepasser mahali], and southern yellow-billed hornbills [Tockus leucomelas]) experiencing daily air temperature maxima (Tmax) ranging from 30°-32°C to 42°-44°C. For none of the three species did Tmax emerge as a significant predictor of elevated fGCM concentrations, and no stress response to simulated hot weather was evident. The apparent lack of a stress response to Tmax = 42°C in captive southern pied babblers contrasts with linear increases in fGCMs at Tmax > 38°C in free-ranging conspecifics. The lack of an effect of Tmax on fGCM levels may potentially be explained by several factors, including differences in operative temperatures and the availability of water and food between free-ranging and captive settings or the stress effect of captivity itself. Our results suggest that experimental manipulations of thermal environments experienced by wild-caught captive birds have limited usefulness for testing hypotheses concerning the effects of hot weather events on fGCM (and, by extension, glucocorticoid) concentrations.

Anthropogenic Influences on Distance Traveled and Vigilance Behavior and Stress-Related Endocrine Correlates in Free-Roaming Giraffes.

Simple SummaryChange in an animal’s behavior due to anthropogenic influences is often expressed in a change in movement patterns and increased vigilance and can result in the secretion of stress-related hormones. However, animals can get habituated to human presence after repeated stimulation. We aimed to obtain a first insight into the effect of human observers on the behavior and stress-related hormone concentrations of free-roaming giraffes as well as their habituation process. Giraffes walked further distances and had elevated fecal glucocorticoid metabolite (fGCM) concentration (stress hormone) in the presence of humans, but anthropogenic influences on their distance walked and fGCM concentration decreased with the increase of habituation. The giraffes were vigilant towards human observers; however, the percentage of time spent on observing a human observer did not decrease with the increase of habituation. Giraffes are an important tourist attraction, and human presence to wildlife is increasing. This has an impact on an animal’s behavior and its endocrine correlates. Studies on other species show alterations in movement patterns, vigilance, and stress-related hormone levels in the presence of humans. Limited information is available on how anthropogenic activities alter giraffe’s behavior, social structure, and related endocrine parameters. The purpose of this study was to obtain insight into anthropogenic influences on giraffe’s behavior and adrenal activity. We used GPS devices mounted onto giraffes to compare the distance walked in the presence or absence of human observers. We also conducted behavioral observations to assess their vigilance and collected fecal samples to analyze their fecal glucocorticoid metabolite (fGCM) concentrations. Giraffes walked significantly further distances in the presence of humans, but the cumulative time that observers were present decreased the hourly distance walked with an observer present, suggesting that the giraffes were becoming habituated. The number of observers present significantly increased the percentage of time spent on observing an observer as well as the number of unhabituated individuals present in the herd. The percentage of time spent observing a human observer did not decrease with the increase of habituation. Last, fGCM concentrations increased with human presence but decreased when individuals became habituated to human presence. More research is needed to understand the effect of anthropogenic influences in different scenarios (e.g., tourism, vehicles, hunting, etc.).

Non-invasive monitoring of glucocorticoid metabolite concentrations in native Indian, as well as captive and re-wilded tigers in South Africa

Over the last century, wild tiger (Panthera tigris) numbers have declined from over 100 000 individuals to fewer than 4 000, with animals now confined to less than 5% of their historic range due to habitat loss, persecution, inadequate management, and poaching. In contrast, 15 000–20 000 tigers are estimated to be housed in captivity, experiencing conditions vastly different than their wild counterparts. A total of 280 tigers are currently held at 44 different facilities within South Africa, including zoos, semi-captive ‘re-wilded’ populations, and pets; these animals provide a unique opportunity to measure the impact of extrinsic factors, found in exotic habitats, on the adrenocortical activity of tigers. By monitoring and comparing stress-related faecal glucocorticoid metabolite (fGCM) concentrations of tigers housed at different locations, and free ranging tigers in natural tiger reserves, this project aimed to get a better understanding of the impact of extrinsic factors on adrenocortical function as a measure of stress. The results of this study showed no significant difference in fGCM concentrations between captive, re-wilded, and free-ranging tigers with the exception of one site. Furthermore, factors such as sex and season were not significant drivers of fGCM concentrations. One study group had elevated fGCM concentrations, showing population variation in the stress response. This indicates that populations are able to cope with exotic environments, however, as population-specific differences in the stress response exist, we suggest management protocols be created for each population. This study offered the unique opportunity to see how well tigers are faring outside of their native range and if having re-wilded tigers in exotic locations is a potential welfare-acceptable management option for tiger conservation globally.

Life on the edge: behavioural and physiological responses of Verreaux's sifakas (Propithecus verreauxi) to forest edges.

Forest edges change micro-environmental conditions, thereby affecting the ecology of many forest-dwelling species. Understanding such edge effects is particularly important for Malagasy primates because many of them live in highly fragmented forests today. The aim of our study was to assess the influence of forest edge effects on activity budgets, feeding ecology, and stress hormone output (measured as faecal glucocorticoid metabolite – fGCM – levels) in wild Verreaux's sifakas (Propithecus verreauxi), a group living, arboreal lemur. We observed five habituated groups: three living in the forest interior and two at an established forest edge. There was no difference in average daily temperatures between edge and interior habitats; however, within the edge site, the average daily temperature incrementally increased over 450 m from the forest edge towards the interior forest of the edge habitat, and the population density was lower at the edge site. Activity budgets differed between groups living in the two microhabitats, with individuals living near the edge spending more time travelling and less time feeding. Groups living near the edge also tended to have smaller home ranges and core areas than groups in the forest interior. In addition, edge groups had elevated average fGCM concentrations, and birth rates were lower for females living in the edge habitat. Combined with lower levels of fruit consumption at the edge, these results suggest that nutritional stress might be a limiting factor for Verreaux's sifakas when living near a forest edge. Hence, Verreaux's sifakas appear to be sensitive to microhabitat characteristics linked to forest edges; a result with implications for the conservation of this critically endangered lemurid species.

Validation of a non-invasive technique for quantifying a stress-associated biomarker in a southern African hornbill

Quantification of glucocorticoids and their metabolites as a central component of the physiological stress response has many potential applications in ornithological research, but require careful species-specific validations. We established a reliable non-invasive method to measure faecal glucocorticoid metabolites (fGCM) in the southern yellow-billed hornbill (Tockus leucomelas). Following an adrenocorticotropic hormone (ACTH) challenge, plasma corticosterone levels increased by 110%, with a tetrahydrocorticosterone enzyme immunoassay (EIA) revealing a ~ fourfold increase in fGCM concentrations approximately 3 h post-injection. These data reveal droppings are a suitable matrix for monitoring stress-associated biomarkers in this species and suggest the tetrahydrocorticosterone EIA may often be appropriate for wild birds.