Faecal Corticosterone Metabolites Levels Research Articles

Assessing space use in meadow voles: the relationship to reproduction and the stress axis

Abstract Voles are key mammals in understanding how social interactions can affect large-scale population processes. Previous studies have shown that at high population densities, meadow voles (Microtus pennsylvanicus) have a lower proportion of breeding animals, higher average corticosterone levels, and can be limited by female territorial spacing. Based on this, we compared corticosterone levels and spatial use between breeding and nonbreeding free-ranging adult meadow voles within populations. We measured intrasexual spatial overlap to examine if breeding females minimize occupying the same areas as other females, and noninvasively assessed corticosterone levels using fecal corticosterone metabolites (FCMs). We found that female meadow voles have much lower intrasexual spatial overlap than males, even though both sexes have similar range sizes, and that females have generally higher FCM levels than males. However, breeding and nonbreeding females did not differ from one another in spatial use or in FCM levels. Conversely, reproductive classes of males differed greatly in all measures: nonbreeding males had FCM levels that were two times higher than those of breeding males, occupied a smaller range, and had lower spatial overlap, indicating they were moving less widely than breeding males. We additionally validated an enzyme immunoassay for noninvasively measuring FCMs in meadow voles. The assay was successful in detecting an increase in corticosterone stimulated by adrenocorticotropic hormone injection; however, dexamethasone did not induce negative feedback. FCMs reflect circulating corticosterone levels approximately 5 h prior. These results highlight differences in FCMs and spacing in meadow voles related to sex and reproductive status, and reflect the respective strategies males and females employ during the breeding season.

Latrine behaviour and faecal corticosterone metabolites as indicators of habitat-related responses of wild rabbits to predation risk

Predation risk avoidance can be of crucial relevance for prey species like the European rabbit (Oryctolagus cuniculus). We evaluated whether the potential predation risk induced by the presentation of red fox (Vulpes vulpes) faeces influenced behavioural and physiological stress responses of rabbits, and whether these responses were modulated by the habitat structure. Fieldwork was carried out in holm oak forests and grasslands where 64 latrines were twice-daily monitored during 5 days (control phase), followed by an experimental phase (5 days) where half of the latrines were treated with red fox faeces and the other half remained as controls. Latrine activity and use were recorded as the percentage of active latrines, the number of days of activity and pellet counts. Further, fresh faecal pellets were daily collected from each latrine and we later quantified fecal corticosterone metabolites (FCM) in the laboratory as an indicator of the animalś physiological stress response. Behavioral and physiological stress responses varied depending on the time of day, during the night latrine activity and use were greater while rabbits showed lower FCM levels. The percentage of active latrines and the number of days of activity significantly decreased during the experimental phase in those latrines treated with red fox faeces. Likewise, pellet counts were noticeably reduced due to red fox faeces but only in holm oak forests. Regarding the physiological stress response, increased FCM levels were found in latrines with fox faeces but this reaction was only found in holm oak forests. These results suggest that, when facing predator cues, the antipredatory strategy of rabbits mainly relies on avoiding risky areas and reducing activity, whereas the physiological stress response seems to be more complex resulting from the synergy of direct (predator faeces) and indirect (habitat traits) cues associated to predation risk.

The landscape of fear: Why some free-ranging rodents choose repeated live-trapping over predation risk and how it is associated with the physiological stress response

Live trapping is an essential element of field ecological studies. However, the act of trapping provides two types of conditional benefits (food from the bait when hungry, and refuge from a predator when threatened) against one type of drawback (confinement). Our understanding of how animals assess the two benefits against the lone risk determines how we interpret classic field studies in chemical ecology and wildlife management. Here, we studied wood mice responses to these risks and rewards of field trapping by examining experience through recapture and faecal corticosterone metabolites (FCM) as a physiological response indicator. Wood mice were live-trapped in two different plots subjected to two distinct phases: phase 1, absence of predator cues, and phase 2, in which traps were treated with red fox faeces. During phase 1, the recapture percentage was lower indicating that mice avoided traps while FCM levels in recaptured mice were higher. On the contrary, during phase 2, despite the total number of captures was lower we found an increase in the recapture percentage and FCM levels did not increase in recaptured mice. Our results suggest that under increased risk perception traps could be likely considered as a suitable shelter and thus, for some individuals the benefits of traps may outweigh their risks. In addition, we discovered that the effects of combining two stressors do not result in the addition of the response originated by each factor separately.

High Arctic lemmings remain reproductively active under predator-induced elevated stress.

Non-consumptive effects of predation have rarely been assessed in wildlife populations even though their impact could be as important as lethal effects. Reproduction of individuals is one of the most important demographic parameters that could be affected by predator-induced stress, which in turn can have important consequences on population dynamics. We studied non-consumptive effects of predation on the reproductive activity (i.e., mating and fertilization) of a cyclic population of brown lemmings exposed to intense summer predation in the Canadian High Arctic. Lemmings were live-trapped, their reproductive activity (i.e., testes visible in males, pregnancy/lactation in females) assessed, and predators were monitored during the summers of 2014 and 2015 within a 9ha predator-reduction exclosure delimited by a fence and covered by a net, and on an 11ha control area. Stress levels were quantified non-invasively with fecal corticosterone metabolites (FCM). We found that FCM levels of lemmings captured outside the predator exclosure (n = 50) were 1.6 times higher than inside (n = 51). The proportion of pregnant/lactating adult females did not differ between the two areas, nor did the proportion of adult scrotal males. We found that lemmings showed physiological stress reactions due to high predation risk, but had no sign of reduced mating activity or fertility. Thus, our results do not support the hypothesis of reproductive suppression by predator-induced stress.

The concentration of fear: mice's behavioural and physiological stress responses to different degrees of predation risk.

Predation is an unavoidable and dangerous fact in the lifetime of prey animals and some sign of the proximity of a predator may be enough to trigger a response in the prey. We investigated whether different degrees of predation risk by red foxes (Vulpes vulpes) evoke behavioural and physiological stress responses in wood mice (Apodemus sylvaticus). We examined the variation in mice responses due to individual factors (sex and reproductive status) and related them to the concentration of the volatile compounds from fox faeces over time. In our experiment, we introduced predation cues into four plots, each subjected to a different concentration treatment (0, 10, 50 and 100% concentration of fresh faeces of red fox), based on the following outline: initial odourless phase 0, phase1 in which predation treatment was renewed daily, and phase 2 in which we renewed the treatment only on the first day. Wood mice were live trapped during all three phases and the physiological response was measured non-invasively by analysing faecal corticosterone metabolites (FCM) in freshly collected faeces. Data were analysed by Generalized Linear Mixed Models. Overall, males were trapped less often than females, and reproductively active individuals from both sexes avoided traps more than non-reproductively active individuals, especially in medium- and high- concentration plots. Variations in FCM concentrations were explained by plot, the interaction between plot and treatment phase, and the interaction between the treatment phase and the reproductive status. During phase 1, we detected a significant rise in FCM levels that increased with predator faecal odour concentration. Additionally, reproductively active individuals showed a strong physiological response during both phases 1 and 2 in all plots, except the control plot. Our results indicated that wood mice are able to discriminate different degrees of predation risk, which allows them to trigger gradual changes in their behavioural and physiological stress responses.

Does ungulate disturbance mediate behavioural and physiological stress responses in Algerian mice ( Mus spretus )? A wild exclosure experiment

Ungulate densities increased recently in Mediterranean oak ecosystem where acorn-dispersing small rodents, like the Algerian mouse ( Mus spretus ), are keystone species. Recent work showed important effects of ungulates on the environment (vegetation and soil characteristics) influencing small mammal behaviour and population dynamics, but little is known on the physiological stress responses of small mammals to ungulates. We studied wild ungulate effects on habitat characteristics and whether ungulate pressure influenced both behavioural and physiological stress responses in wild populations of Algerian mice. We manipulated ungulates' presence by large exclosures in Holm oak Quercus ilex open woodland with paired controls, where live trapping of Algerian mice was combined with a detailed evaluation of relevant habitat features for this rodent species such as vegetation height, cover and soil compaction. Further we analysed faecal corticosterone metabolites (FCM) in captured Algerian mice to test whether ungulate presence led to increased glucocorticoids. Fresh faecal samples from 92 different individuals captured with Sherman live traps were collected and analyzed by an enzyme immunoassay. Mouse abundance was higher inside ungulate exclosures due to positive exclosure effects on understory vegetation cover and soil compaction. Mice selected smaller trees with more area covered by resprouts, and this selection was stronger outside than inside exclosures. FCM levels were higher in females than in males. FCM levels were positively correlated with soil compaction and inversely with tree canopy size; however, individuals showed higher FCM levels inside than outside exclosures probably due to the higher local mouse abundance inside exclosures. Mouse behaviour varied in relation to direct effects of wild ungulates on key habitat traits whereas physiological stress responses seemed to be mediated by the increased intraspecific competition, an indirect effect of wild ungulates.

Foraging, feeding, and physiological stress responses of wild wood mice to increased illumination and common genet cues.

In nature, animals are exposed to a broad range of threats imposed by predators, which may strongly influence the ecology of prey species directly or indirectly by affecting their behavior via fear of predation. Here, we studied wood mice Apodemus sylvaticus behavioral and physiological responses to simulated predation risk. Risk avoidance was analyzed by live trapping with control traps and traps treated with feces of common genet Genetta genetta (direct cue of risk) under new moon nights and following by simulated full moon conditions (indirect cue). The time devoted to foraging behavior and capture time were analyzed by video recording mice activity around traps. Food intake was calculated based on the amount of bait remaining in each trap. Fecal corticosterone metabolites (FCMs) were measured by enzyme-immunoassay as indicators of physiological stress responses. Fewer wood mice were captured during full moon, yet only non-breeding adult males clearly avoided common genet odor. Mice were captured sooner at night during the simulated full moon conditions and later in predator-treated traps. Foraging activity was lower when individuals faced predator’s feces, but neither food intake nor FCM levels were affected by predation risk cues. Direct and indirect cues of predation risk selectively affected wood mice behavior, although behavioral responses seem to be modulated by different costs–benefit balances related to the individual’s perception of risk. The lack of physiological responses to predation risk cues suggests that wood mice did not perceive them as reliable stressors or the response was too small or transient to be measured by FCM.

Prevalence and determinants of stereotypic behaviours and physiological stress among tigers and leopards in Indian zoos.

India’s charismatic wildlife species are facing immense pressure from anthropogenic-induced environmental perturbations. Zoos play a major role in the conservation of threatened species, but their adaptation in captivity is posing a major challenge globally. Stress from inadequate adaptation could lead to suppression of cognitive functioning and increased display of stereotypic behaviour. It is thus necessary to measure biological traits like behaviour, stress physiology, and contextual factors driving the animals maintained at zoos. In this study, we assessed stereotypic behaviour and stress physiology employing standard behaviour scoring, non-invasive stress monitoring, and their contextual drivers in a sub-population of two large felid species managed in six Indian zoos. The prevalence and intensity of stereotypic behaviours and levels of faecal corticosterone metabolites (FCM) were ascertained among 41 Royal Bengal tigers Panthera tigris tigris and 21 Indian leopards Panthera pardus fusca between April 2014 and March 2015. Behavioural observations showed that tigers spent more time stereotyping (12%) than leopards (7%) during daylight hours. Stress levels assessed using FCM revealed that tigers (23.6 ± 1.62 ng/g) had marginally lower level of corticosterone metabolites than leopards (27.2 ±1.36 ng/g). Stereotypic behaviour increased significantly with FCM level when the effect of heath status was controlled in tigers, and the effects tree cover, stone, den and keeper attitude controlled in leopards. Comparison of stereotypes of tigers with various biological and environmental factors using binary logistic regression revealed that stereotypic prevalence decreased with increased enclosure size, and enclosure enrichments like presence of pools and stones, when managed socially with conspecifics, and with positive keeper attitude, these factors accounting for 43% of variations in stereotypic prevalence among tigers. Stereotype among leopards was significantly absent when associated with increased tree cover and presence of pool, and den in the enclosure, age and among zoo-born than wild-born ones. These factors explain 81% of variations in stereotypic prevalence in them. A comparison of FCM levels with context-dependent factors revealed that stress levels among tigers decreased significantly with enclosure size and with individuals from nil to low, and severity of health issues. These factors explain 64% of variations in FCM levels. In leopards, the presence of stones in the enclosure and keepers with positive attitude resulted in significant decrease in FCM levels, these factors together accounting for 94% of variations. Multiple regressions on selected variables based on Factor Analysis of Mixed Data showed that in tigers the intensity of stereotype decreased significantly with enclosure size, sociality and positive keeper attitude and FCM level with health problems. Similarly, analyses in leopards revealed that intensity of stereotype decreased significantly with tree cover, age and FCM level with positive keeper attitude. Overall, our study suggests that to reduce stereotypes and stress level, tigers in captivity should be managed in larger enclosures enriched with pool, and stones, and in appropriate social conditions with adequate veterinary care. Leopards should be managed in enclosures with dense tree cover, pool, stones and den. Positive keeper attitude plays a crucial role in the welfare of both the species in captivity. Our study is promising and is comparable with their natural behaviour in the wild; for example, tigers require larger natural habitats, while leopards can manage even with smaller isolated patches but with dense vegetation cover.

Faecal corticosterone responses of black rhinos (Diceros bicornis) to a transfer between housing facilities within a zoo

Faecal corticosterone metabolites (FCM) of four black rhinos ( Diceros bicornis ) at Magdeburg Zoo in Germany were investigated to assess the stress level associated with an internal transfer of rhinos between housing facilities. Moving rhinos within the zoo led to a punctual increase of FCM concentrations in three animals. We observed no signs of a period of acclimatisation, such as increased FCM levels for several days or longer periods. Increased FCM levels of one out of three rhinos re-investigated one year after the enclosure change, may be related to the reproductive status of this female (five to six months before parturition). The moderate FCM response patterns found in this study indicate that the transfer of rhinos between enclosures at Magdeburg Zoo was minimally invasive.

Corticosterone metabolites in laying hen droppings—Effects of fiber enrichment, genotype, and daily variations

There is growing interest and concern for animal welfare in commercial poultry production. To evaluate stress and welfare in an objective and noninvasive way, fecal corticosterone metabolites (FCM) in droppings can be analyzed. However, the influence of diet, genotype, and daily variations in FCM and production of droppings in laying hens has been poorly investigated. This study examined the effect of insoluble fiber by adding 3% ground straw pellets to the feed to Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) hens housed in furnished cages between 20 and 40 wk of age. In total, 960 hens were included in the study. Droppings were collected 4 times per day for 3 consecutive days and analyzed by corticosterone immunoassay. Biological validation confirmed the ability of the assay to detect changes in FCM levels. Inclusion of straw pellets in the feed increased FCM concentration in both hen genotypes and increased excretion rate of FCM in LB hens. The LB hens also produced greater amounts of droppings than LSL hens. Both FCM levels and production of droppings varied during the day, although no distinct diurnal rhythm was found. These findings demonstrate that when using FCM to evaluate stress and welfare in laying hens, many factors (e.g., diet, genotype used, and so on) need to be taken into account to allow accurate interpretation of the results. In addition, under certain conditions, excretion rate of FCM might be more appropriate to use compared with FCM concentration.

Does predation risk, through moon phase and predator cues, modulate food intake, antipredatory and physiological responses in wood mice (Apodemus sylvaticus)?

Predation influences the ecology and behaviour of prey species and it is well known that the risk of predation affects prey’s decision making. We investigated whether predation risk through moon phase and exposure to the faecal odour of a natural predator, the red fox Vulpes vulpes, affect feeding behaviour and physiological response in wood mice (Apodemus sylvaticus). Antipredatory response was studied by live trapping under new and full moon in odourless control areas and areas experimentally manipulated with red fox fresh faeces. Food intake by individuals was determined as the amount of bait remaining in each trap and the physiological response was measured non-invasively analysing faecal corticosterone metabolites (FCM). Traps treated with faeces of red fox were the most avoided, and this avoidance was more significant during full moon. Food intake by wood mice varied according to the moon phase being significantly lower under full moon nights. We found sex, breeding condition and weight of individuals explaining the variation found in FCM concentrations, but no changes in FCM levels due to moon phase or exposure to red fox faeces were detected. These results indicate that wood mice avoid red fox faecal odour and this antipredatory response as well as feeding behaviour are significantly influenced by moon phase. However, no physiological response was found due to predation risk suggesting that wood mice do not take these predation cues enough reliable to experience physiological changes.

Are Motorways Potential Stressors of Roadside Wood Mice (Apodemus sylvaticus) Populations?

Linear infrastructures represent one of the most important human impacts on natural habitats and exert several effects on mammal populations. Motorways are recognized as a major cause of habitat fragmentation and degradation and of biodiversity loss. However, it is unknown whether motorways lead to increased physiological stress reactions in wild animal populations. We analysed faecal corticosterone metabolites (FCM) in wild populations of wood mice (Apodemus sylvaticus) living in a well-preserved Mediterranean agro-pastoral woodland at different distances (verge, 500 m and 1000 m) from the AP-51 motorway in Spain. Wood mice were captured with Sherman live traps, and fresh faecal samples from 424 individuals were collected and analyzed in the laboratory. The quantification of FCM was performed by a 5α-pregnane-3β,11β, 21-triol-20-one enzyme immunoassay. Results showed that females had higher FCM levels than males, and these levels were higher in breeding females. In addition, FCM levels were positively correlated with body weight of individuals. Wood mice captured where cattle were present showed higher FCM levels than individuals living where cattle were not detected. FCM levels were higher in non-breeding individuals living close to the motorway compared with FCM levels in those individuals captured further from the motorway. This is the first study showing evidence of the motorways' impact on physiological stress reactions in wild wood mice populations. Understanding how free-living animals are influenced by human interventions could help to understand other subtle changes observed in wild animal populations. Since mice are used world-wide as research models these results could open new perspectives testing human influence on the natural environment and trade-offs of species in degraded ecosystems.

Variation in faecal corticosterone metabolites in an Arctic seabird, the Little Auk (Alle alle) during the nesting period

Glucocorticoids participate in the control of whole body homoeostasis and an organism’s response to stress. Corticosterone, which is the principal glucocorticoid in birds, has been shown to increase in response to different energetic demands and perturbations that individuals have to cope with. In this study, a non-invasive method to examine the corticosterone secretion by measuring faecal corticosterone metabolites (FCM) has been established for an Arctic seabird, the Little Auk (Alle alle). A group-specific immunoassay was successfully validated for adults and chicks using an adrenocorticotropic challenge test. Then, FCM levels were investigated under different energetic and physiological demands, determined by weather conditions, week of chick rearing in adults, and age in chicks. The amount of rainfall had no effect on FCM levels in adults, whereas it negatively affected FCM levels in chicks. There was no variation in FCM concentrations among weeks of chick rearing in adults. In chicks, the FCM levels increased with age. Moreover, chicks with higher FCM levels had lower body mass and fledged later than chicks with lower FCM levels. This study demonstrates that environmental stress such as poor weather conditions can trigger significant changes in corticosterone levels in seabird chicks. Furthermore, the results indicate that corticosterone may be involved in the physiological and behavioural adjustments necessary for successful fledging and post-fledging survival.

Environmental Enrichment Alters Splenic Immune Cell Composition and Enhances Secondary Influenza Vaccine Responses in Mice

Chronic stress has deleterious effects on immune function, which can lead to adverse health outcomes. However, studies investigating the impact of stress reduction interventions on immunity in clinical research have yielded divergent results, potentially stemming from differences in study design and genetic heterogeneity, among other clinical research challenges. To test the hypothesis that reducing glucocorticoid levels enhances certain immune functions, we administered influenza vaccine once (prime) or twice (boost) to mice housed in either standard control caging or environmental enrichment (EE) caging. We have shown that this approach reduces mouse corticosterone production. Compared with controls, EE mice had significantly lower levels of fecal corticosterone metabolites (FCMs) and increased splenic B and T lymphocyte numbers. Corticosterone levels were negatively associated with the numbers of CD19(+) (r(2) = 0.43, p = 0.0017), CD4(+) (r(2) = 0.28, p = 0.0154) and CD8(+) cells (r(2) = 0.20, p = 0.0503). Vaccinated mice showed nonsignificant differences in immunoglobulin G (IgG) titer between caging groups, although EE mice tended to exhibit larger increases in titer from prime to boost than controls; the interaction between the caging group (control versus EE) and vaccine group (prime versus boost) showed a strong statistical trend (cage-group*vaccine-group, F = 4.27, p = 0.0555), suggesting that there may be distinct effects of EE caging on primary versus secondary IgG vaccine responses. Vaccine-stimulated splenocytes from boosted EE mice had a significantly greater frequency of interleukin 5 (IL-5)-secreting cells than boosted controls (mean difference 7.7, IL-5 spot-forming units/10(6) splenocytes, 95% confidence interval 0.24-135.1, p = 0.0493) and showed a greater increase in the frequency of IL-5-secreting cells from prime to boost. Our results suggest that corticosterone reduction via EE caging was associated with enhanced secondary vaccine responses, but had little effect on primary responses in mice. These findings help identify differences in primary and secondary vaccine responses in relationship to stress mediators that may be relevant in clinical studies.

Are degraded habitats from agricultural crops associated with elevated faecal glucocorticoids in a wild population of common vole (Microtus arvalis)?

The severe impact of agriculture on species’ abundance and diversity is widely recognized. However, its effects on the physiology of wild animal populations are poorly known. We analyzed faecal glucocorticoids levels in wild common voles (Microtus arvalis) living in a farmland landscape to test whether living in degraded habitats, such as crops, is correlated with increased glucocorticoids. Other factors such as sex, reproductive status, and population density were also considered. We captured voles with Sherman traps in crops and in their field margins which were comprised of semi-natural vegetation. We collected fresh faecal samples from captured individuals and quantified their levels of faecal corticosterone metabolites (FCM) in the laboratory. The quantification of FCM concentrations was performed by competitive enzyme immunoassay. Individuals captured within the crops had higher levels of FCM than those in field margins; females and breeding individuals exhibited higher FCM levels. In addition, FCM concentrations positively correlated with abundance of voles. Our results suggest that degraded habitats in agricultural landscapes are associated with increased glucocorticoid levels on common voles likely caused by a higher disturbance from agricultural practices and a lesser vegetation cover in crops compared with field margins.

Fecal glucocorticoid metabolites in wild yellow-bellied marmots: Experimental validation, individual differences and ecological correlates

Natural selection is expected to shape phenotypic traits that permit organisms to respond appropriately to the environments in which they live. One important mechanism by which animals cope with changes in their environment is through physiological responses to stressors mediated by glucocorticoid hormones. Here we perform biological and physiological validations of a minimally-invasive technique for assessing fecal corticosterone metabolites (FCMs) in captive and wild groups of yellow-bellied marmots (Marmota flaviventris). Then we draw from ten years of data on these obligate hibernators at the Rocky Mountain Biological Laboratory in Colorado, USA to assess the extent to which seasonal and daily changes explain naturalistic variation in baseline levels of FCMs. Interestingly, beyond important population-level variation with respect to year, season, time of day, sex, age and reproductive state, we found repeatable inter-individual differences in FCMs, suggesting this hormonal trait might be a meaningful target of selection. FCM levels were 68% lower in captive than wild marmots, suggesting that the natural environment in which these animals occur is generally more challenging or less predictable than life in captivity. Most live-trapping events failed to represent stressors for wild marmots such that repeated measurements of traits were possible with minimal “stress” to subjects. We also document the natural ranges of annual and seasonal variation necessary for understanding the extent to which anthropogenic assaults represent stressors for wild mammals. Taken together, this study provides a foundation for understanding the evolution of hormonal traits and has important welfare and conservation implications for field biologists.

Do social statuses affect the startle reflex in male mice?

Usual housing conditions lead to dominance hierarchy forming between male mice. The situation produces physiological and behavioural differences between dominants and subordinates. The goal of the present study was to assess stress responses, and possible changes in prepulse inhibition (PPI) of the startle reflex in dominant and subordinate male mice. Three weeks of daily social interactions led to stable aggressive dominance in 11 pairs of male NMRI mice. Stress levels were assessed by measuring faecal corticosterone metabolites (FCM), a non-invasive technique for monitoring hormonal changes in response to specific situations, with repeated sampling of each animal. The analysis of FCM levels showed greater stress in subordinate males at the beginning of the experiment, as the hierarchy was being established, but by the end of the experiment, FCM levels were reduced and similar in both dominants and subordinates. No significant differences were found in the startle response or PPI.

Contrasting fecal corticosterone metabolite levels in captive and free‐living colonial tuco‐tucos (Ctenomys sociabilis)

The environment in which an animal lives can profoundly influence its biology, including physiological responses to external stressors. To examine the effects of environmental conditions on physiological stress reactions in colonial tuco-tucos (Ctenomys sociabilis), we measured glucocorticoid (GC) levels in captive and free-living members of this species of social, subterranean rodent. Analyses of plasma and fecal samples revealed immunoreactive corticosterone (metabolites) to be the most prevalent GC in this species. An adrenocorticotropic hormone challenge confirmed that fecal corticosterone metabolites are responsive to exogenous stressors and provided validation of the commercial enzyme immunoassay kit used to detect these metabolites. Comparisons of adult female C. sociabilis from natural and captive environments revealed significantly higher baseline concentrations of corticosterone metabolites and significantly greater individual variation in metabolite concentrations among free-living animals. These findings suggest that the natural environment in which these animals occur is more challenging and more variable than the captive housing conditions employed. In addition to providing the first evaluation of GC levels in captive and wild colonial tuco-tucos, our findings indicate that the influence of environmental conditions on stress physiology may have important implications for understanding the social behavior of this species in the laboratory and the field.

Stability of Avian Fecal Corticosterone Metabolite Levels in Frozen Avian Feces

ABSTRACT Fecal corticosterone metabolites are commonly used in avian ecology as a measure of response to stress. Recent research on mammals suggested that the manner in which samples are stored could be critical to alleviating any storage handling bias. Cross‐reacting metabolites can increase glucocorticoid metabolites even after samples are frozen and, thus, result in an overestimation of hormone levels as the time increases between when samples were collected and when levels are measured. We examined effects of sample storage time on fecal corticosterone metabolites for 2 avian species across 165 days. We observed no change in fecal corticosterone metabolites across the sampling periods in either fulvous whistling‐ducks (Dendrocygna bicolor) or white ibis (Eudocimus albus). Results suggest that avian fecal corticosterone metabolite levels do not change when samples are frozen for long periods of time and that there were no differences in the response between the 2 species we compared. This study demonstrated that avian fecal corticosterone samples are accurate even after freezing and, thus, studies that seek to address conservation questions may rely on these data. Studies of additional bird species are needed to generalize our findings to other avian taxa.

Ski tourism affects habitat use and evokes a physiological stress response in capercaillie Tetrao urogallus: a new methodological approach

Summary Human outdoor recreational activities are increasing and have a significant impact on wildlife. There are few methods suitable for investigating the response of rare and endangered species to human recreational activities, although the impact can be assessed at various scales by measuring both physiological and behavioural responses to disturbance. Capercaillie Tetrao urogallus are suffering strong population declines throughout central Europe. We examined the effects of ski tourism on capercaillie habitat use and adrenocortical activity, measured non‐invasively in droppings. During three winters, 2003–06, we radio‐tracked 13 capercaillie. In the southern Black Forest in Germany, we sampled 396 droppings of these and additional individuals before and after the start of the ski season. We tested whether the intensity of human winter recreational activities affected home range location and habitat use, and we identified those factors influencing the concentration of corticosterone metabolites (CM) in droppings. Capercaillie used habitats subject to ski tourism. Although the latter did not affect home range location, capercaillie preferred undisturbed forests within their home ranges and avoided areas with high recreation intensity in the ski season. Faecal CM levels of individuals in areas with low recreation intensity were significantly lower than those in areas with moderate or high recreation intensity during the entire study period. We conclude that ski tourism affects both habitat use and endocrine status in capercaillie, with potential negative consequences on body condition and overall fitness. Synthesis and applications. This study demonstrates the relevance of studying wildlife responses at various temporal and spatial scales, and the value of using multiple methods applied to the same individuals to monitor the impact of human recreational activities on a free‐ranging species. In order to protect capercaillie populations, we recommend that managers keep forests inhabited by capercaillie free from tourism infrastructure and retain undisturbed forest patches within skiing areas.