Fecal Glucocorticoid Concentrations Research Articles

Stress in wildlife: comparison of the stress response among domestic, captive, and free-ranging animals.

The stress response, which involves joint activity of the nervous and endocrine systems, is one of the basic adaptive mechanisms that ensures the survival of the individual. The activation of the sympathetic nervous system, the sympathetic-adrenal-medullary axis, and the hypothalamic-pituitary-adrenal axis enables organisms to respond to endogenous and exogenous challenges. Repeated short-term stress leads to long-term stress, which disrupts physiological homeostasis. Unlike domestic animals, wild animals are not protected from environmental and weather influences or treated for diseases. In addition, climate change, habitat fragmentation and loss, and urban stressors (such as light, noise and chemical pollution; xenobiotics; traffic; and buildings) affect individual wildlife and populations. In this review, we have attempted to depict the magnitude of the stress response in wildlife and related domestic animals as well as in captive and free-ranging animals. The intensity of the stress response can be estimated by determining the concentration of glucocorticoids in body fluids, tissues, and excreta. A comparison of results from different studies suggests that domestic animals have lower fecal and hair glucocorticoid concentrations than related wild animals. Additionally, fecal and hair glucocorticoid concentrations in captive animals are higher than in free-ranging animals of the same species. As there are limited data on this topic, we cannot draw definitive conclusions about glucocorticoid concentration and stress response. Further studies are needed to clarify these issues.

Assessing variation in faecal glucocorticoid concentrations in gray whales exposed to anthropogenic stressors.

Understanding how individual animals respond to stressors behaviourally and physiologically is a critical step towards quantifying long-term population consequences and informing management efforts. Glucocorticoid (GC) metabolite accumulation in various matrices provides an integrated measure of adrenal activation in baleen whales and could thus be used to investigate physiological changes following exposure to stressors. In this study, we measured GC concentrations in faecal samples of Pacific Coast Feeding Group (PCFG) gray whales (Eschrichtius robustus) collected over seven consecutive years to assess the association between GC content and metrics of exposure to sound levels and vessel traffic at different temporal scales, while controlling for contextual variables such as sex, reproductive status, age, body condition, year, time of year and location. We develop a Bayesian Generalized Additive Modelling approach that accommodates the many complexities of these data, including non-linear variation in hormone concentrations, missing covariate values, repeated samples, sampling variability and some hormone concentrations below the limit of detection. Estimated relationships showed large variability, but emerging patterns indicate a strong context-dependency of physiological variation, depending on sex, body condition and proximity to a port. Our results highlight the need to control for baseline hormone variation related to context, which otherwise can obscure the functional relationship between faecal GCs and stressor exposure. Therefore, extensive data collection to determine sources of baseline variation in well-studied populations, such as PCFG gray whales, could shed light on cetacean stress physiology and be used to extend applicability to less-well-studied taxa. GC analyses may offer greatest utility when employed as part of a suite of markers that, in aggregate, provide a multivariate measure of physiological status, better informing estimates of individuals' health and ultimately the consequences of anthropogenic stressors on populations.

Comparing Space Use and Fecal Glucocorticoid Concentrations during and after the COVID-19 Closure to Investigate Visitor Effects in Multiple Species

We used the COVID-19 pandemic closure at the Saint Louis Zoo to examine visitor effects on space use and glucocorticoid levels in banteng, grizzly bears, polar bears, and western lowland gorillas. The study was divided into four six-week phases: closure in spring 2020, reopening in summer 2020, fall 2020, and spring 2021 as a seasonal comparison. Space use data were collected using video, and fecal samples were assayed for glucocorticoids. Generalized linear models were used to examine differences in zone occupancy and glucocorticoids between phases. The banteng spent more time near visitors, and glucocorticoids were only temporarily elevated in two of five animals when visitors returned. The grizzly bears spent more time in their habitat than in the den, and the polar bear spent more time near viewing areas after visitors returned. Glucocorticoids did not differ significantly between the closure and reopening for any bears. The gorillas spent less time close to visitors immediately after reopening but this effect waned by fall; glucocorticoid data were not available. Overall, based on space use and glucocorticoid levels, we suggest visitor effects on the gorillas are neutral, on the grizzly bears are neutral or positive, and are positive on the banteng and polar bear.

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.

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.

Costs of seasonality at a southern latitude: Behavioral endocrinology of female baboons in the Cape Peninsula of South Africa

Environmental challenges in the form of temperature extremes and unusual precipitation, which may lead to prolonged periods outside the thermoneutral zone, can be detrimental to animal physiology. Chacma baboons in the Cape Peninsula of South Africa, one of the highest latitudes at which nonhuman primates are found, experience extremes of both temperature and rainfall, as well as seasonal differences in day length that require animals to condense their daily routine into dramatically reduced daylight hours. Here we examine the effects of these climatic factors on the behavior (activity budgets and foraging patterns) and physiology (fecal glucocorticoid concentrations) of adult females (N = 33) in three groups of chacma baboons (Papio ursinus) inhabiting the Cape Peninsula, where temperatures ranged from 7 to 39 °C, monthly rainfall ranged from 2 to 158 mm, and day length varied by 4.5 h across seasons. Climatic variables showed a clear relationship to female baboon glucocorticoid concentrations, which significantly increased with lower temperatures, higher rainfall and shorter day lengths. Activity budgets also differed between summer and winter, with females generally spending less time socializing, moving and resting in the winter compared to summer, with some differences between troops in their feeding-related activities. Cold temperatures accompanied by rainfall and short day lengths may thus represent an ecological constraint for this population. This study highlights the potential impact of anthropogenic climate change on the physiology, behavior, and, ultimately, survival of wildlife populations.

Glucocorticoid exposure predicts survival in female baboons.

Are differences in hypothalamic-pituitary-adrenal (HPA) axis activation across the adult life span linked to differences in survival? This question has been the subject of considerable debate. We analyze the link between survival and fecal glucocorticoid (GC) measures in a wild primate population, leveraging an unusually extensive longitudinal dataset of 14,173 GC measurements from 242 adult female baboons over 1634 female years. We document a powerful link between GCs and survival: Females with relatively high current GCs or high lifelong cumulative GCs face an elevated risk of death. A hypothetical female who maintained GCs in the top 90% for her age across adulthood would be expected to lose 5.4 years of life relative to a female who maintained GCs in the bottom 10% for her age. Hence, differences among individuals in HPA axis activity provide valuable prognostic information about disparities in life span.

Behavioral and physiological responses to instability in group membership in wild male woolly monkeys (Lagothrix lagotricha poeppigii).

In group-living species, integrating into a new social group after dispersal is an important life history milestone associated with physical and social challenges. Generally, this process seems to be accompanied by heightened glucocorticoid (GC) concentrations; however, most studies of physiological responses to group transfer have been conducted on species with despotic social relationships, where integrating individuals are often targets of frequent aggression. Here we present data on fecal glucocorticoid (fGC) concentrations during periods of unstable group membership for male woolly monkeys (Lagothrix lagotricha poeppigii), a species with extremely low rates of male-male aggression and generally tolerant male-male associations. We collected data on males in four study groups at the Tiputini Biodiversity Station, Ecuador, and observed three attempted transfer events, involving a total of four adult males, in one study group. We observed only three instances of overt aggression (chases) between males across the entire study period, though male display behaviors were more frequent. We tested whether rates of displays were higher during periods of unstable group membership using a generalized linear mixed model (LMM). We also examined whether male status, group stability, and the occurrence of intergroup encounters affected fGC concentrations using LMMs. Contrary to our predictions, rates of display behaviors were not higher during periods of unstable group membership. However, both transient/integrating males and those who were already group members showed elevated fGC concentrations during these unstable periods. Our results suggest that even in species with tolerant male-male relationships, the integration of unfamiliar individuals can provoke an increase in GCs.

Higher dominance rank is associated with lower glucocorticoids in wild female baboons: A rank metric comparison

In vertebrates, glucocorticoid secretion occurs in response to energetic and psychosocial stressors that trigger the hypothalamic-pituitary-adrenal (HPA) axis. Measuring glucocorticoid concentrations can therefore shed light on the stressors associated with different social and environmental variables, including dominance rank. Using 14,172 fecal samples from 237 wild female baboons, we test the hypothesis that high-ranking females experience fewer psychosocial and/or energetic stressors than lower-ranking females. We predicted that high-ranking females would have lower fecal glucocorticoid (fGC) concentrations than low-ranking females. Because dominance rank can be measured in multiple ways, we employ an information theoretic approach to compare 5 different measures of rank as predictors of fGC concentrations: ordinal rank; proportional rank; Elo rating; and two approaches to categorical ranking (alpha vs non-alpha and high-middle-low). Our hypothesis was supported, but it was also too simplistic. We found that alpha females exhibited substantially lower fGCs than other females (typical reduction = 8.2%). If we used proportional rank instead of alpha versus non-alpha status in the model, we observed a weak effect of rank such that fGCs rose 4.2% from the highest- to lowest-ranking female in the hierarchy. Models using ordinal rank, Elo rating, or high-middle-low categories alone failed to explain variation in female fGCs. Our findings shed new light on the association between dominance rank and the stress response, the competitive landscape of female baboons as compared to males, and the assumptions inherent in a researcher's choice of rank metric.

Asymmetric reproductive aging in cheetah (Acinonyx jubatus) females in European zoos

For conservation breeding and management, such as re-introduction programs, reproductively healthy animals are essential. Low reproductive performance in captive animals is therefore of great concern in species which are judged to be vulnerable or endangered in the wild. Hence, it is important to understand the mechanisms that lead to low reproductive performance in captivity. Here we use a long-term study on captive cheetah females as an example to test predictions derived from three hypotheses –, the captive ‘stress’, captive reproductive suppression and asymmetric reproductive aging hypotheses. Parous and nulliparous cheetah females did not differ in their faecal glucocorticoid concentrations, suggesting that allostatic load (‘stress’) did not affect reproductive performance. Consistent with the captive reproduction suppression hypothesis, females permanently kept together with other adult females (or males) did not reproduce until they were individually introduced to a single male when in estrus. Instead, reproductive performance of twelve cheetah females kept in zoological gardens and followed throughout their lifetime was determined by their age and reproductive history, as predicted by the asymmetric reproductive aging hypothesis. Asymmetric reproductive aging arises when first breeding attempts and first pregnancies of females are substantially delayed, thereby ensuring frequent cycle fluctuations of oestrogen concentrations which subsequently result in reproductive tract pathologies. Our results suggest that conservation breeding facilities should breed cheetah females as early as possible, keep them separate from adult males or other females and introduce them to single males for breeding purposes when in estrus only.

Effect of Artificial Piglet Suckling Sounds on Behavior and Performance of Piglets and Adrenal Responses of Sows.

Operation of the farrowing house is essential to the productivity of a swine farm, requiring not only good management but also knowledge of the behavior of sows and piglets. Stress can negatively affect production in farm animals and could be a factor in production indexes. The objective of this study was to investigate the effect of artificial sucking sounds on the behavior of piglets and fecal glucocorticoid (FGM) concentrations of sows. A total of 30 sows were divided into two groups: a treatment group (15 sows) was exposed to artificial sucking sounds and a control group (15 sows) was not. Both groups received the same management; the two open-house system locations were separated by a distance of about 270 meters. The study had three key objectives: to compare farrowing indexes and to observe the sucking behavior of piglets using CCTV cameras. Fecal samples were collected daily for 21 days from the period after parturition to weaning to assess adrenal activity. The treatment group had a significantly higher average number of times piglets came to a sow's udder, and sows had a shorter onset time for the first piglet to come to the sow's udder than the control group (both P<0.05). The patterns and levels of FGM between the two groups were not different (both P<0.05), but the treatment group had better farrowing indexes than the control group (P>0.05), particularly for litter weight gain and percent preweaning mortality. In addition, the weaning to first service interval of the treatment group was shorter than the control group (P<0.05). This indicates that the artificial suckling sound probably has no adverse effect on adrenal responses of pig; however, it improves production indexes of postparturition sows.

Interbirth intervals in wild baboons: Environmental predictors and hormonal correlates.

Interbirth intervals (IBIs) are a key metric of female reproductive success; understanding how they are regulated by environmental, social, and demographic factors can provide insight into sources of variance in female fitness. Using 36 years of reproductive data on 490 IBIs for 160 wild female baboons, we identified sources of variance in the duration of IBIs and of their component phases: postpartum amenorrhea (PPA), sexual cycling, and pregnancy. We also examined how body fat and fecal hormone concentrations varied during female IBIs. We found that IBIs tended to be shorter (reproduction was accelerated) when female traits and environmental variables promoted energy acquisition, but with different specific effects for different component phases of the IBI. We also found that females lost a substantial amount of body fat during PPA, indicating that PPA imposes accumulating energetic costs as it progresses. Prior to cycle resumption females began to regain body fat; body fat was stable across the cycling phase and increased throughout most of pregnancy. However, body fat scores per se were not associated with the duration of any of the component phases. Finally, we found that fecal glucocorticoid concentrations decreased as PPA progressed, suggesting a decline in energetic stress over this phase. Fecal progestogen and estrogen concentrations changed over time during sexual cycling; the direction of these changes depended on the phase of the sexual cycle (luteal versus early or late follicular phases). Our study lends insight into the energetic constraints on female primate reproduction, revealing how female environments, changes in body fat, and steroid hormone concentrations relate to IBI duration and to reproductive readiness.

Physiological stress responses to natural variation in predation risk: evidence from white sharks and seals

Predators can impact ecosystems through consumptive or risk effects on prey. Physiologically, risk effects can be mediated by energetic mechanisms or stress responses. The predation-stress hypothesis predicts that risk induces stress in prey, which can affect survival and reproduction. However, empirical support for this hypothesis is both mixed and limited, and the conditions that cause predation risk to induce stress responses in some cases, but not others, remain unclear. Unusually clear-cut variation in exposure of Cape fur seals (Arctocephalus pusillus pusillus) to predation risk from white sharks (Carcharodon carcharias) in the waters of Southwestern Africa provides an opportunity to test the predation-stress hypothesis in the wild. Here, we measured fecal glucocorticoid concentrations (fGCM) from Cape fur seals at six discrete islands colonies exposed to spatiotemporal variation in predation risk from white sharks over a period of three years. We found highly elevated fGCM concentrations in seals at colonies exposed to high levels of unpredictable and relatively uncontrollable risk of shark attack, but not at colonies where seals were either not exposed to shark predation or could proactively mitigate their risk through antipredatory behavior. Differences in measured fGCM levels were consistent with patterns of risk at the site and seasonal level, for both seal adults and juveniles. Seal fGCM levels were not correlated with colony population size, density, and geographic location. Investigation at a high risk site (False Bay) also revealed strong correlations between fGCM levels and temporal variation in shark attack rates, but not with shark relative abundance. Our results suggest that predation risk will induce a stress response when risk cannot be predicted and/or proactively mitigated by behavioral responses.

Non‐invasive physiological markers demonstrate link between habitat quality, adult sex ratio and poor population growth rate in a vulnerable species, the Cape mountain zebra

Abstract Effective conservation and species management require an understanding of the causes of poor population growth. Conservation physiology uses biomarkers to identify factors that contribute to low individual fitness and population declines. Building on this, macrophysiology can use the same markers to assess how individual physiology varies with different ecological or demographic factors over large temporal and spatial scales. Here, we use a macrophysiological approach to identify the ecological and demographic correlates of poor population growth rates in the Cape mountain zebra metapopulation. We use two non‐invasive biomarkers: faecal glucocorticoids as a measure of chronic stress, and faecal androgens as an indicator of male physiological status. We found that faecal glucocorticoid concentrations were highest in the spring prior to summer rainfall, and were elevated in individuals from populations associated with low‐quality habitat (lower grass abundance). In addition, faecal androgen concentrations were higher in populations with a high proportion of non‐breeding stallions (where male:female adult sex ratios exceed 2:1) suggesting sex ratio imbalances may intensify male competition. Finally, population growth rate was negatively associated with faecal glucocorticoid concentrations and female fecundity was negatively associated with faecal androgens, indicating a relationship between hormone profiles and fitness. Together, our results provide cross‐population evidence for how poor population growth rates in Cape mountain zebra can be linked to individual physiological biomarkers. More broadly, we advocate physiological biomarkers as indicators of population viability, and as a way to evaluate the impact of variable ecological and demographic factors. In addition, conservation physiology can be used to assess the efficacy of management interventions for this subspecies, and this approach could inform models of species’ responses to future environmental change. A plain language summary is available for this article.

Female Spider Monkeys (Ateles geoffroyi) Cope with Anthropogenic Disturbance Through Fission-Fusion Dynamics.

Most primates live in habitats with some level of anthropogenic disturbance, and such disturbances have a larger impact on frugivorous primates that are more sensitive to ecological disruptions than folivores. Fecal glucocorticoid metabolites provide insight into how the external environment affects internal physiological state, and thus provide information on how anthropogenic pressures become embodied. Here, I examine how subgroup size and glucocorticoids vary with high and low fruit abundance, and how fruit abundance, subgroup size, and activity budget affect fecal glucocorticoid metabolites in female spider monkeys (Ateles geoffroyi) living in an anthropogenically disturbed habitat. I measured these variables via behavioral, ecological, and fecal sampling for 15 months in 17 female spider monkeys at El Zota Biological Field Station. Subgroup size was significantly larger during periods of high fruit abundance, but glucocorticoids did not differ between periods of low and high fruit abundance. Monthly fruit abundance predicted subgroup sizes significantly, but did not predict fecal glucocorticoid concentrations. Increased resting time and reproductive state predicted fecal glucocorticoid concentrations significantly, but travel and foraging time had no significant effect on glucocorticoid concentrations. Individual resting time over the study period correlated negatively with glucocorticoid concentrations. These results suggest that spider monkeys cope with variation in fruit abundance by adjusting subgroup size, and that these adjustments may mitigate environmental stress in this mildly seasonal environment. The large, relatively productive forest size at this site, and the availability of anthropogenic food sources, enable this population of spider monkeys to cope with human-induced habitat disturbance.

Heart rate, heart rate variability, faecal glucocorticoid metabolites and avoidance response of dairy cows before and after changeover to an automatic milking system.

The heart rate variability (HRV) parameters of dairy cows were monitored during parlour (PARL) and the later installed automatic (AMS) milking on a small-scale commercial dairy farm in Hungary. The aim of the study was to assess stress in relation to the type of milking and the frequency of human interaction. Parlour milking involved regular moving and crowding of the animals with frequent human interaction, which were much less frequent in automatic milking. The first phase of the study was conducted prior to the changeover [n = 27] and the second two months afterwards [n = 19 (of the cows from the first phase)]. Heart rate (HR) was recorded by the Polar RS800 CX recording system. HRV parameters indicative of sympathovagal balance were calculated for periods of lying and standing in the barn, waiting before milking and milking, respectively. Morning and evening faecal glucocorticoid concentrations were also measured. Fear of humans was tested by an avoidance distance test. Baseline HRV parameters showed no difference (P > 0.05) between the two systems. In the periods before, during and after milking a higher sympathetic tone was detected in cows in the PARL phase. Mean faecal glucocorticoid concentrations were higher at the time of parlour milking. The avoidance distance did not differ between the two phases. The results suggest that automatic milking might be less stressful for cows than parlour milking, possibly due to the shorter duration of restraint after milking and the less frequent human interaction.

Use of fecal glucocorticoid and salivary cortisol concentrations as a measure of well-being of New York City carriage horses.

OBJECTIVE To use noninvasive approaches to assess stress in New York City (NYC) carriage horses during the course of their daily routine to determine whether use of these horses affected their well-being. DESIGN Prospective case control study. ANIMALS 13 (5 mares and 8 geldings) stabled working NYC carriage horses and 5 pastured (nonworking) NYC carriage horses (1 mare and 4 geldings). PROCEDURES Samples for determination of fecal glucocorticoid and salivary cortisol concentrations were collected on 3 successive days from 10, 8, and 9 working carriage horses during rest (time 1), preparation for work (time 2), and return to the stable (time 3) and at 1 hour after work (time 4). Infrared thermography (IRT) measurements were made to determine maximum temperature of the medial canthus at each time point. Fecal samples were also collected from 5 pastured carriage horses for determination of glucocorticoid concentrations. RESULTS No difference was found in mean ± SE fecal glucocorticoid concentrations between pastured (22.1 ± 9.8 ng/g) and working (19.5 ± 4.2 ng/g) carriage horses. A significant difference was found in salivary cortisol concentrations of working carriage horses between time 3 (0.96 ± 0.06 ng/mL) and time 4 (0.77 ± 0.07 ng/mL). The IRT measurement at time 2 (35.5 ± 0.64°C [95.9 ± 1.2°F]) was significantly lower than that at time 3 (36.2 ± 0.64°C [97.1 ± 1.2°F]). No other differences in IRT measurements were found. CONCLUSIONS AND CLINICAL RELEVANCE These working NYC carriage horses did not have physiologic responses indicative of a negative welfare status.

Elevated glucocorticoid concentrations during gestation predict reduced reproductive success in subordinate female banded mongooses.

Dominant females in social species have been hypothesized to reduce the reproductive success of their subordinates by inducing elevated circulating glucocorticoid (GC) concentrations. However, this ‘stress-related suppression' hypothesis has received little support in cooperatively breeding species, despite evident reproductive skews among females. We tested this hypothesis in the banded mongoose (Mungos mungo), a cooperative mammal in which multiple females conceive and carry to term in each communal breeding attempt. As predicted, lower ranked females had lower reproductive success, even among females that carried to term. While there were no rank-related differences in faecal glucocorticoid (fGC) concentrations prior to gestation or in the first trimester, lower ranked females had significantly higher fGC concentrations than higher ranked females in the second and third trimesters. Finally, females with higher fGC concentrations during the third trimester lost a greater proportion of their gestated young prior to their emergence from the burrow. Together, our results are consistent with a role for rank-related maternal stress in generating reproductive skew among females in this cooperative breeder. While studies of reproductive skew frequently consider the possibility that rank-related stress reduces the conception rates of subordinates, our findings highlight the possibility of detrimental effects on reproductive outcomes even after pregnancies have become established.

Heart Rate Variability as an Indicator of Chronic Stress Caused by Lameness in Dairy Cows.

Most experimental studies on animal stress physiology have focused on acute stress, while chronic stress, which is also encountered in intensive dairy cattle farming–e.g. in case of lameness–, has received little attention. We investigated heart rate (HR) and heart rate variability (HRV) as indicators of the autonomic nervous system activity and fecal glucocorticoid concentrations as the indicator of the hypothalamic–pituitary–adrenal axis activity in lame (with locomotion scores 4 and 5; n = 51) and non-lame (with locomotion scores 1 and 2; n = 52) Holstein-Friesian cows. Data recorded during the periods of undisturbed lying–representing baseline cardiac activity–were involved in the analysis. Besides linear analysis methods of the cardiac inter-beat interval (time-domain geometric, frequency domain and Poincaré analyses) non-linear HRV parameters were also evaluated. With the exception of standard deviation 1 (SD1), all HRV indices were affected by lameness. Heart rate was lower in lame cows than in non-lame ones. Vagal tone parameters were higher in lame cows than in non-lame animals, while indices of the sympathovagal balance reflected on a decreased sympathetic activity in lame cows. All geometric and non-linear HRV measures were lower in lame cows compared to non-lame ones suggesting that chronic stress influenced linear and non-linear characteristics of cardiac function. Lameness had no effect on fecal glucocorticoid concentrations. Our results demonstrate that HRV analysis is a reliable method in the assessment of chronic stress, however, it requires further studies to fully understand the elevated parasympathetic and decreased sympathetic tone in lame animals.

Reproduction, aging and mortality rate in social subterranean mole voles (Ellobius talpinus Pall.).

Eusocial subterranean rodents of the Bathyergidae family have enormous longevity. The long lifespan of these species is associated with negligible senescence, that is, an absence of the signs of age-related deterioration in physical condition. The question arises as to whether these features are unique to eusocial Bathyergids or typical of other social subterranean rodents as well. In the present study, we analysed data from observations of a social subterranean Microtinae rodent, the northern mole vole (Ellobius talpinus Pall.), which, like mole-rats, has reproductive skew. Among the individuals captured in the wild and maintained in captivity, females that reproduced lived significantly longer than non-breeding females. We did not find any changes in muscle strength with age in any of the demographic groups studied. Faecal glucocorticoid concentrations before death were significantly higher in non-breeding females than in breeding females and males. Increased adrenocortical activity may be one mechanism responsible for the decreased lifespan of non-reproducing individuals of social subterranean rodents. We conclude that the patterns of aging, although different in some respects, are generally common for social subterranean rodents of different taxonomic groups.