Can faecal glucocorticoid metabolites be used to monitor body condition in wild Upland geese Chloephaga picta leucoptera?

Seasonal Hair Glucocorticoid Fluctuations in Wild Mice (Phyllotis darwini) within a Semi-Arid Landscape in North-Central Chile

Mammals in drylands face environmental challenges exacerbated by climate change. Currently, human activity significantly impacts these environments, and its effects on the energy demands experienced by individuals have not yet been determined. Energy demand in organisms is managed through elevations in glucocorticoid levels, which also vary with developmental and health states. Here, we assessed how anthropization, individual characteristics, and seasonality influence hair glucocorticoid concentration in the Darwin's leaf-eared mouse (Phyllotis darwini) inhabiting two areas with contrasting anthropogenic intervention in a semi-arid ecosystem of northern Chile. Hair samples were collected (n = 199) to quantify hair corticosterone concentration (HCC) using enzyme immunoassays; additionally, sex, body condition, and ectoparasite load were recorded. There were no differences in HCC between anthropized areas and areas protected from human disturbance; however, higher concentrations were recorded in females, and seasonal fluctuations were experienced by males. The results indicate that animals inhabiting semi-arid ecosystems are differentially stressed depending on their sex. Additionally, sex and season have a greater impact on corticosterone concentration than anthropogenic perturbation, possibly including temporal factors, precipitation, and primary production. The influence of sex and seasonality on HCC in P. darwini make it necessary to include these variables in future stress assessments of this species.

A Review of Non-Invasive Sampling in Wildlife Disease and Health Research: What's New?

In the last decades, wildlife diseases and the health status of animal populations have gained increasing attention from the scientific community as part of a One Health framework. Furthermore, the need for non-invasive sampling methods with a minimal impact on wildlife has become paramount in complying with modern ethical standards and regulations, and to collect high-quality and unbiased data. We analysed the publication trends on non-invasive sampling in wildlife health and disease research and offer a comprehensive review on the different samples that can be collected non-invasively. We retrieved 272 articles spanning from 1998 to 2021, with a rapid increase in number from 2010. Thirty-nine percent of the papers were focussed on diseases, 58% on other health-related topics, and 3% on both. Stress and other physiological parameters were the most addressed research topics, followed by viruses, helminths, and bacterial infections. Terrestrial mammals accounted for 75% of all publications, and faeces were the most widely used sample. Our review of the sampling materials and collection methods highlights that, although the use of some types of samples for specific applications is now consolidated, others are perhaps still underutilised and new technologies may offer future opportunities for an even wider use of non-invasively collected samples.

Faecal Glucocorticoid Metabolites and H/L Ratio are Related Markers of Stress in Semi-Captive Asian Timber Elephants

Simple Summary

Animals are kept in captivity for various reasons worldwide. Throughout its range countries, the Asian elephant is used for various purposes, with a significant proportion of the remaining population working as draft and transport animals in the timber industry. However, captivity can also lead to compromises in welfare that need to be quantified for successful intervention. A key way of assessing an animal’s well-being in wildlife and zoo biology is to measure its stress. Previous studies have found positive, negative, or no relationship between two commonly used measures of stress: stress hormones and the ratio of two types of white blood cells—heterophils to lymphocytes. Our study is one of the first to show a positive and consistent link between these two measures in semi-captive Asian elephants from Myanmar, irrespective of sex, age, or environmental context. Our results show that using the heterophil/lymphocyte ratio from blood smears on-site may offer a potentially cheaper and faster way to determine stress than measuring faecal glucocorticoid metabolite concentrations in the laboratory.

Abstract

Animals are kept in captivity for various reasons, but species with a slower pace of life may adapt to captive environments less easily, leading to welfare concerns and the need to assess stress reliably in order to develop effective interventions. Our aim was to assess welfare of semi-captive timber elephants from Myanmar by investigating the relationship between two physiological markers of stress commonly used as proxies for welfare, faecal glucocorticoid metabolite concentrations (FGM) and heterophil/lymphocyte ratios (H/L), and link these measures to changes in body condition (determined by body weight). We further assessed how robustly these two markers of stress performed in animals of different age or sex, or in different ecological contexts. We measured FGM concentrations and H/L ratios between 2016 and 2018 from 316 samples of 75 females and 49 males ranging in age from 4 to 68. We found a positive and consistent link between FGMs and H/L ratios in Asian elephants, irrespective of their sex, age, or ecological context. Our results will help to inform managers of (semi-) captive elephants about using heterophil/lymphocyte ratio data from blood smears on site as a potentially cheaper and faster alternative to determining stress than measuring faecal glucocorticoid metabolite concentrations in the laboratory.

Monitoring corticoid metabolites in urine of white-tailed sea eagles: Negative effects of road proximity on breeding pairs

The white-tailed sea eagle (Haliaeetus albicilla) is known to be sensitive to disturbance. To better understand potential stressors, we measured corticosterone metabolite levels in H. albicilla excreta and recorded the nest success of breeding pairs. We tested the ability of four enzyme immunoassays (EIA) to measure urinary glucocorticoid metabolites (uGM) in the excreta of one adult female eagle subjected to a controlled physiological stress treatment. We identified corticosterone-21-HS to be the most sensitive EIA to changes in uGM concentration. To exclude a sex bias, we confirmed the assay's applicability with samples collected from similar stress treatments in two juvenile males. We used the identified EIA to measure uGM in wild breeding pairs and tested effects of disturbance. Breeding pairs nesting closer to roads and paths had higher uGM concentrations (p = 0.02), which is likely an effect of human recreational activity and disturbance. There was no difference in uGM concentrations between failed and successful nests. Our results highlight the potential impact of road and path proximity on white-tailed sea eagles, with potential importance for species management and conservation, particularly with respect to nest protection zone legislation.

Assessment of season-dependent body condition scores in relation to faecal glucocorticoid metabolites in free-ranging Asian elephants

We studied seasonal and annual changes in visual body condition scores (BCSs), and assessed how these scores were related to levels of faecal glucocorticoid metabolites (fGCMs) in free-ranging Asian elephants (Elephas maximus) in the seasonally dry tropical forests of the Mysore and Nilgiri Elephant Reserves in southern India. We assessed the animals' BCS visually on a scale of 1 to 5; where 1 represents a very thin and 5 represents a very fat elephant. To understand the influence of seasonality on BCS, we sampled the population during dry (n = 398) and wet seasons (n = 255) of 2013 and 2015 while, for annual changes in BCS, we sampled nine free-ranging adult females from different family groups that had been repeatedly sighted over seven years. To evaluate the influence of body condition on fGCM, 307 faecal samples were collected from 261 different elephants and were analysed. As a parameter of adrenocortical activity, and thus stress, fGCM was measured (μg/g) in the ethanol-extracted samples using a group-specific 11-oxoaetiocholanolone EIA (antibody raised against 11-oxoaetiocholanolone-17-CMO:BSA and biotinylated-11-oxoaetiocholanolone as a label). Effect of age and season on BCS in relation to fGCM was also studied. A seasonal shift in BCS was observed as expected, i.e. individuals with low BCS were more frequent during the dry season when compared with the wet season. Concentrations of fGCM were highest in individuals with lowest BCS (BCS 1) and then significantly declined till BCS 3. fGCM levels were almost comparable for BCS 3, 4 and 5. This pattern was more conspicuous in female than in male elephants. Season-dependent BCS, hence, reflect the stress status as measured by fGCM, especially in female Asian elephants. This could be used as an important non-invasive approach to monitor the physiological health of free-ranging elephant populations.

Feather corticosterone reveals effect of moulting conditions in the autumn on subsequent reproductive output and survival in an Arctic migratory bird

For birds, unpredictable environments during the energetically stressful times of moulting and breeding are expected to have negative fitness effects. Detecting those effects however, might be difficult if individuals modulate their physiology and/or behaviours in ways to minimize short-term fitness costs. Corticosterone in feathers (CORTf) is thought to provide information on total baseline and stress-induced CORT levels at moulting and is an integrated measure of hypothalamic-pituitary-adrenal activity during the time feathers are grown. We predicted that CORTf levels in northern common eider females would relate to subsequent body condition, reproductive success and survival, in a population of eiders nesting in the eastern Canadian Arctic during a capricious period marked by annual avian cholera outbreaks. We collected CORTf data from feathers grown during previous moult in autumn and data on phenology of subsequent reproduction and survival for 242 eider females over 5 years. Using path analyses, we detected a direct relationship between CORTf and arrival date and body condition the following year. CORTf also had negative indirect relationships with both eider reproductive success and survival of eiders during an avian cholera outbreak. This indirect effect was dramatic with a reduction of approximately 30% in subsequent survival of eiders during an avian cholera outbreak when mean CORTf increased by 1 standard deviation. This study highlights the importance of events or processes occurring during moult on subsequent expression of life-history traits and relation to individual fitness, and shows that information from non-destructive sampling of individuals can track carry-over effects across seasons.

Stress assessment in captive greylag geese (Anser anser)

Chronic stress--or, more appropriately, "allostatic overload"--may be physiologically harmful and can cause death in the most severe cases. Animals in captivity are thought to be particularly vulnerable to allostatic overload due to artificial housing and group makeup. Here we attempted to determine if captive greylag geese (Anser anser), housed lifelong in captivity, showed elevated levels of immunoreactive corticosterone metabolites (CORT) and ectoparasites in dropping samples as well as some hematological parameters (hematocrit, packed cell volume, total white blood cell count [TWBC], and heterophil:lymphocyte ratio [H:L]). All of these have been measured as indicators of chronic stress. Furthermore, we correlated the various stress parameters within individuals. Captive geese showed elevated values of CORT and ectoparasites relative to a wild population sampled in the vicinity of the area where the captive flock is held. The elevated levels, however, were by no means at a pathological level and fall well into the range of other published values in wild greylag geese. We found no correlations between any of the variables measured from droppings with any of the ones collected from blood. Among the blood parameters, only the H:L negatively correlated with TWBC. We examine the problem of inferring allostatic overload when measuring only 1 stress parameter, as there is no consistency between various measurements taken. We discuss the different aspects of each of the parameters measured and the extensive individual variation in response to stress as well as the timing at which different systems respond to a stressor and what is actually measured at the time of data collection. We conclude that measuring only 1 stress parameter often is insufficient to evaluate the well-being of both wild and captively housed animals and that collecting behavioral data on stress might be a suitable addition.

Faecal glucocorticoid metabolite concentrations in the free-ranging bandicoots (Perameles nasuta and Isoodon obesulus) of northern Sydney

Knowledge of how animals cope with their environment is fundamental to the management of free-ranging populations. Urban animals face increased competition for resources, habitat fragmentation and predation. These pressures may impact an individual’s welfare by releasing glucocorticoid hormones in the blood through a response from the hypothalamic–pituitary–adrenal axis, resulting in altered energy storage and utilisation. This study aimed to determine the applicability of measuring faecal glucocorticoid metabolites in free-ranging bandicoots by using a simple enzyme immunoassay. We used long-nosed and southern brown bandicoots in northern Sydney to investigate whether environmental and demographic variables can influence faecal glucocorticoid metabolites. Long-nosed bandicoots showed similar faecal glucocorticoid metabolite concentrations between suburban backyards and National Park populations. Higher faecal glucocorticoid metabolites were recorded in female southern brown bandicoots than in males, whilst female and male long-nosed bandicoots had similar glucocorticoid metabolite levels. Ectoparasite load, body condition and season did not influence faecal glucocorticoid metabolites. This non-invasive method has a broad application and can be used to provide biological information to guide management of populations within a conservation context.