Non-invasive fecal hormone analysis and behavioral observations for monitoring stress responses in captive western lowland gorillas (Gorilla gorilla gorilla)

Quality of hematology and clinical chemistry results in laboratory and zoo nonhuman primates: Effects of the preanalytical phase. A review

Most errors in clinical pathology originate in the preanalytical phase, which includes all steps from the preparation of animals and equipment to the collection of the specimen and its management until analyzed. Blood is the most common specimen collected in nonhuman primates. Other specimens collected include urine, saliva, feces, and hair. The primary concern is the variability of blood hematology and biochemistry results due to sampling conditions with the effects of capture, restraint, and/or anesthesia. Housing and diet have fewer effects, with the exception of food restriction to reduce obesity. There has been less investigation regarding the impact of sampling conditions of nonblood specimens.

Impact of alternating overnight housing conditions on welfare measures in a bachelor group of western lowland gorillas (Gorilla gorilla gorilla)

Spatial parameters and design of overnight housing spaces can have significant influences on both nocturnal and diurnal behaviors of western lowland gorillas (Gorilla gorilla gorilla) in captivity. This is especially true for bachelor groups, as adult males have demonstrated a greater tendency to separate from conspecifics overnight. Additionally, previous studies have suggested that the social needs of individuals in bachelor units may shift over time. The bachelor unit at the Detroit Zoo is managed in a unique hybrid strategy in which the group is housed socially for three nights (either indoors or indoors with outdoor access), then separately on the fourth. A 2016 study of this group (n = 3) suggested that individuals had better welfare following social overnight housing as compared to solitary overnight housing. We aimed to reassess how overnight housing conditions affect individual welfare several years later. We revised a previously developed qualitative behavioral assessment tool that included 13 behavioral items spanning both positive and negative indicators of welfare. Animal care staff completed the assessment and collected a fecal sample every day for each gorilla for a period of 3 months. We used Kruskal-Wallis tests to analyze variation in behavioral items and FGMs between conditions. We then used generalized linear mixed models to identify whether overnight housing condition or other potentially confounding variables were driving observed variation in welfare indicators. We found significant variation demonstrating significantly better welfare indicators after being housed separately as compared to being socially housed indoors overnight. Although separate housing appears to be the ideal condition for this group at this point in time, if seasonality permits, social housing with outdoor access may be a feasible alternative to consistent overnight separation for these gorillas.

A composite menstrual cycle of captive orangutans, with associated hormonal and behavioral variability

Knowledge of species-typical reproductive endocrinology profiles is crucial for testing hypotheses pertaining to the evolutionary history, reproductive parameters, and life history of a species, and for managing the well-being of individual animals in human care. Large-scale empirical measurements of ovarian hormones, however, are rare for most primate species, including orangutans. In this study, we used enzyme immunoassays (EIA) to quantify estrogen (estrone conjugates; E₁ C) and progesterone (pregnanediol-3-glucuronide; PdG) levels for 98 cycles in 7 cycling zoo-housed female orangutans (10-43 years old). We use a subset of these cycles (N = 44) to create the first composite menstrual cycle for orangutans, which serves as a valuable baseline for future comparative analyses and veterinary considerations. Similar to previous studies, we determined the mean ovarian cycle length of orangutans to be 29.7 days (N = 98 cycles), although we illustrate evidence of both intra- and interindividual variation in ovarian steroid production. Given that this study took place in captivity, we consider how energetic and psychosocial aspects of the zoo environment, such as greater food availability and potential stress, may affect the reproductive physiology and sexual behavior of these females. Furthermore, we discuss the role that age and genetic background may play in producing variability. Finally, we test whether ovarian hormone levels correlate with the reproductive behaviors of these female orangutans using associated behavioral data. Our results suggest that matings are more common during the periovulatory period than outside of it, but do not support a consistent link between hormonal indices of fecundability and mating behaviors in these individuals.

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.

Monitoring stress in captive and free-ranging African wild dogs (Lycaon pictus) using faecal glucocorticoid metabolites

An understanding of stress physiology is important for species management because high levels of stress can hamper reproduction and affect an individual's ability to cope with threats to their survival, such as disease and human-wildlife conflict. A commonly used indicator of stress, faecal concentrations of cortisol metabolites (FCM), can be used to assess the impact of social, biological and environmental factors. Measurements of FCM are particularly valuable for endangered species that are logistically challenging to study and where non-invasive techniques are preferred. As the second most endangered canid in Africa, the African wild dog (Lycaon pictus) has been the focus of considerable conservation research, yet there is still little understanding of factors associated with stress, in either captive or free-ranging populations. The present study therefore aimed to determine whether stress levels differ between captive and free-ranging populations, and to detect social, biological and environmental factors that are stressful in these populations. Faecal samples were collected from 20 captive and 62 free-ranging animals. Within free-ranging populations, the sexes differed significantly, but there was no effect of social status, age or breeding period for either sex. Captive females had higher FCM concentrations than free-ranging females. In captive populations, FCM concentrations differed among zoos and with reproductive status in females, but were not related to age class or group-housing structure. In conclusion, FCM is a useful indicator of stress and should be considered an integrative aspect of management, for both in situ and ex situ African wild dog populations.

Baseline levels of faecal glucocorticoid metabolites and indications of chronic stress in the vulnerable grey-headed flying-fox, Pteropus poliocephalus

The physiological stress hormone levels and physical condition of captured urban flying-foxes experiencing a food shortage were compared with those of free-living rural flying-foxes with access to supplementary food. Glucocorticoid hormone levels were determined by measuring glucocorticoid metabolites (GCMs) from the faeces of individual animals. The rural flying-foxes were in good condition with high Body Condition Indexes (BCIs) and low levels of GCMs, the range of which may be considered the baseline for this species. In comparison, urban flying-foxes had lower BCIs and elevated levels of GCMs: 75% had levels that were higher than the rural range and 30% were higher by an order of magnitude. Such elevated levels of glucocorticoid (‘stress’) hormones are characteristic of chronic stress. While urbanisation can cause chronic stress, given the low BCIs observed, it is more likely that food shortage was the major stressor in this study. While the rural male and female flying-foxes showed no significant differences in either their levels of faecal glucocorticoid metabolites or their BCIs, significantly different results were found between male and female urban flying-foxes: males were in relatively better condition than females but had higher levels of faecal glucocorticoid metabolites. The autumn and winter reproductive constraints on food-restricted flying-foxes probably explain the differences observed. Additional droppings collected under the urban colony gave similar results to those collected from captured flying-foxes at the same location, and could be a useful non-invasive method for determining the levels of physiological stress in flying-fox colonies.

Ethical considerations in hibernation research

Ethical research practices are a key component of scientific integrity and of public support for research. Hibernation research presents specific ethical issues in regard to animal welfare. In this article, the authors apply the '3Rs' principles of humane experimental technique (replacement, reduction and refinement) to hibernation research. They provide recommendations for hibernation researchers and suggest future directions for addressing issues specific to hibernation research. They discuss the use of appropriate behavioral and physiological monitoring procedures, the development of species-specific brain atlases for placement of brain probes, the provision of environmental enrichment and the management of studies involving pharmacological induction of torpor. Addressing these issues in hibernation research will lead to improvements in research outcomes and in welfare of hibernating species.

Validation of a field technique and characterization of fecal glucocorticoid metabolite analysis in wild chimpanzees (Pan troglodytes)

Monitoring adrenocortical activity in wild primate populations is critical, given the well-documented relationship between stress, health, and reproduction. Although many primate studies have quantified fecal glucocorticoid metabolite (FGM) concentrations, it is imperative that researchers validate their method for each species. Here, we describe and validate a technique for field extraction and storage of FGMs in wild chimpanzees (Pan troglodytes). Our method circumvents many of the logistical challenges associated with field studies while yielding similar results to a commonly used laboratory method. We further validate that our method accurately reflects stress physiology using an adrenocorticotropic hormone challenge in a captive chimpanzee and an FGM peak at parturition in a wild subject. Finally, we quantify circadian patterns for FGMs for the first time in this species. Understanding these patterns may allow researchers to directly link specific events with the stress response.

Non-invasive monitoring of physiological stress in the Western lowland gorilla (Gorilla gorilla gorilla): validation of a fecal glucocorticoid assay and methods for practical application in the field

Enzymeimmunoassays (EIAs) allow researchers to monitor stress hormone output via measurement of fecal glucocorticoid metabolites (FGCMs) in many vertebrates. They can be powerful tools which allow the acquisition of otherwise unobtainable physiological information from both captive animals and wild animals in remote forest habitats, such as great apes. However, methods for hormone measurement, extraction and preservation need to be adapted and validated for field settings. In preparation for a field study of Western lowland gorillas (Gorilla gorilla gorilla) in the Central African Republic we used samples from captive gorillas collected around opportunistic stressful situations to test whether four different glucocorticoid EIAs reflected adrenocortical activity reliably and to establish the lag-time from the stressor to peak excretion. We also validated a field extraction technique and established a simple, non-freezer-reliant method to preserve FGCMs in extracts long-term. We determined the rate of FGCM change over 28 days when samples cannot be extracted immediately and over 12h when feces cannot be preserved immediately in alcohol. Finally, we used repeat samples from identified individuals to test for diurnal variation in FGCM output. Two group-specific assays measuring major cortisol metabolites detected the predicted FGCM response to the stressor reliably, whereas more specific cortisol and corticosterone assays were distinctly less responsive and thus less useful. We detected a lag time of 2-3 days from stressor to peak FGCM excretion. Our field extraction method performed as well as an established laboratory extraction method and FGCMs in dried extracts stored at ambient temperatures were as stable as those at -20 °C over 1 yr. Hormones in non-extracted feces in alcohol were stable up to 28 days at ambient temperatures. FGCMs in un-fixed gorilla feces deteriorated to almost 50% of the original values within 6h under field conditions. We detected no diurnal variation in FGCMs in samples from wild gorillas. Our study highlights the importance of thorough biological and immunological validation of FGCM assays, and presents validated, practical methods for the application of non-invasive adrenocortical monitoring techniques to field conservation contexts where it is crucially needed.

Relationship between behavior, adrenal activity, and environment in zoo-housed western lowland gorillas (Gorilla gorilla gorilla)

Monitoring adrenal activity through noninvasive fecal hormone sampling is rapidly gaining popularity as a tool to assess zoo animal welfare. However, few studies have sought to investigate the interrelationships between behavior, adrenal activity, and environment, and ask whether both behavioral and adrenal monitoring strategies are required to assess welfare sufficiently. We present the findings of a 9-month study of a small group (one male, two females) of Western lowland gorillas, Gorilla gorilla gorilla. First, we examined the effect of environmental variables on gorilla behavior. Second, we examined the effect of environmental variables on the concentration of fecal glucocorticoid metabolites (FGC) and the relationship between behavior and FGC. Environmental variables had similar effects on all three gorillas. Negative vigilance of visitors (NVV; staring, posturing, and charging at visitors) significantly increased in all subjects as environmental noise levels increased, and food-related behavior significantly decreased in all subjects as crowd size increased. Exhibit modifications had a number of positive effects on behavior. Notably, when privacy screens were used, NVV significantly decreased in two subjects. We found no significant effects of environmental variables on FGC. However, we did find significant relationships between behavior and FGC in one female. Specifically, her NVV was significantly higher one day before, and on the same day as, raised FGC. Also, hair plucking significantly increased in the two days following raised FGC. Overall, this study demonstrates how concurrent noninvasive fecal and behavioral monitoring can be used for gorilla welfare assessment.

Rates of self-directed behaviour and faecal glucocorticoid levels are not correlated in female wild olive baboons (Papio hamadryas anubis)

Non-invasive methods to quantify components of stress in non-human animals rely typically on the use of physiological or behavioural measures. At the physiological level, stress is usually measured non-invasively in terms of faecal or urinary glucocorticoid output. A common group of behavioural measures used are self-directed behaviours (SDBs), which have been shown to be linked to anxiety, a subset of stress, although a number of authors have explicitly linked SDBs to stress more generally. Whether increased rates of SDBs are likely to be associated with increased faecal glucocorticoid ouput in wild mammals remains unclear. Here, for wild female olive baboons, we show no association between day-to-day changes in levels of SDB and cortisol metabolite excretion. We also show no relationship between long-term mean levels of these variables. We discuss several possible interpretations of our results, including the possibility that SDBs represent a behavioural coping mechanism, helping to ameliorate the physiological stress response.