Beneficial effect of hot spring bathing on stress levels in Japanese macaques

Hormonal changes in northern white-cheeked gibbons (Nomascus leucogenys) after the death of a group member

The small apes, gibbons and siamangs, are monogamous species with their social groups comprising of both parents and their offspring. Therefore, the loss of a member may elicit a stress response in the remaining members due to their strong bonds. Glucocorticoids (GCs) have been useful indicators of stress, but distinguishing between acute versus chronic stress may be limited when measuring these hormones alone. The adrenal hormone dehydroepiandrosterone-sulfate (DHEAS), a GC antagonist, has been implicated in the regulation of the stress response. Thus, the concomitant measurement of these hormones can help examine whether an event, such as the loss of a group member, elicited a stress response. In this brief report, we discuss the hormonal response of two zoo-housed northern white-cheeked gibbons (Nomascus leucogenys) (1 adolescent male and his mother) after the death of the adult male of the group. Baseline fecal samples were collected opportunistically from these two individuals 5 months prior, and 3 months following the death of their group member. A total of 25 samples were quantified for fecal GC metabolites (FGCMs) and DHEAS by enzyme immunoassay (EIA) to calculate the FGCMs:DHEAS ratio. Our results indicate an increase in FGCMs and FGCMs:DHEAS for the adolescent male, but not the adult female, following the death. Our findings suggest that the integration of FGCMs and DHEAS measurements can provide valuable information to interpret individual stress levels to the sudden change in the group's social structure.

Housing relocation does not have to induce a significant stress response in captive Japanese macaques (Macaca fuscata)

BACKGROUND

Previous studies suggest that housing relocation may be stressful for captive non-human primates. Our study investigated the stress levels of Japanese macaques during a housing relocation by measuring their daily fecal cortisol metabolites, which are often used as an indicator of stress.

METHODS

Ten adult Japanese macaques, single-housed for research purposes, were relocated to a new facility. Fecal samples were collected daily for 7 days. Cortisol metabolite concentrations were determined via enzyme immunoassay.

RESULTS

No significant differences in cortisol metabolite levels were found in 7 days, but concentration levels showed that the highest median was associated to the relocation day.

CONCLUSIONS

The minimal cortisol metabolite increase suggests that there was a slight activity increase in the hypothalamic-pituitary-adrenal axis. Techniques encouraging cooperation of the monkeys, the short time duration of the relocation, and consistency in the environment may have contributed to the minimal stress levels observed.

Coping styles vary with species' sociality and life history: A systematic review and meta-regression analysis

Despite a long history of animal studies investigating coping styles, the causal connections between behavior and stress physiology remain unclear. Consistency across taxa in effect sizes would support the idea of a direct causal link maintained by either functional or developmental dependencies. Alternatively, lack of consistency would suggest coping styles are evolutionarily labile. Here, we investigated correlations between personality traits and baseline and stress-induced glucocorticoid levels using a systematic review and meta-analysis. Most personality traits did not consistently vary with either baseline or stress-induced glucocorticoids. Only aggression and sociability showed a consistent negative correlation with baseline glucocorticoids. We found that life history variation affected the relationship between stress-induced glucocorticoid levels and personality traits, especially anxiety and aggression. The relationship between anxiety and baseline glucocorticoids depended on species' sociality with solitary species showing more positive effect sizes. Thus, integration between behavioral and physiological traits depends on species' sociality and life history and suggests high evolutionary lability of coping styles.

Mothers of disabled infants had higher cortisol levels in a free-ranging group of Japanese macaques (Macaca fuscata)

Glucocorticoids (GCs) are hormones released in response to stressors and can provide insight into an organism's physiological well-being. Experiencing chronic challenges to homeostasis is associated with significant deviations from baseline fecal GCs (fGCs) in many species, providing a noninvasive biomarker for assessing stress. In the group of free-ranging Japanese macaques (Macaca fuscata) at the Awajishima Monkey Center in Japan, ~17% have congenital limb malformations. We collected 646 fecal samples from 27 females over three consecutive birth seasons (May-August) and analyzed them using enzyme immunoassay to extract fGCs. We explored the relationship between fGC levels and individual (physical impairment and reproductive status), social (dominance rank and availability of kin for social support), and ecological variables (exposure to potential predators, rainfall, and wild fruit availability). A disabled infant was associated significantly with higher fGC in the mother; however, physical impairment in adult females was not significantly related to fGC levels. Females with higher dominance rank had significantly lower fGC levels than lower ranking females. Other factors did not relate significantly to fGC. These results suggest that providing care that meets the support needs of disabled infants poses a physiological challenge for mothers and suggests that physically impaired adults are able to effectively compensate for their disabilities with behavioral plasticity. Once an individual with congenital limb malformations survives infancy through their mother's care, physical impairment does not appear to influence fGC values, while social variables like dominance rank significantly influenced cortisol values in free-ranging female Japanese macaques.

Reducing stress and stereotypic behaviors in captive female pygmy slow lorises (Nycticebus pygmeaus)

Improving captive conditions of pygmy slow lorises (Nekaris and Nijman have recently suggested that the pygmy slow loris should be called the pygmy loris and is distinctive enough to warrant a new genus, Xanthonycticebu) (Nycticebus pygmeaus) poses many challenges because detailed aspects of their lives in the wild are incomplete. This hinders efforts to replicate sustainable environments for them. To improve their well-being in captivity, eight rescued female pygmy slow lorises at the Japan Monkey Center (JMC) were socially housed in two types of groups following their solitary housing: two pairs and one group of four individuals. They spent much of their time in affiliative behaviors, as well as sharing sleeping sites after placement in a social group. The purpose of my study was to examine whether social housing helped in reducing stress by comparing fecal glucocorticoids and stereotypic behaviors when housed alone and when with conspecifics. Overall, the levels of fecal glucocorticoids were significantly lower when socially housed than when kept alone. One individual exhibited stereotypic behavior when housed alone, but this behavior disappeared after social housing. These findings support recent evidence that pygmy slow lorises are social animals and will benefit from group housing in captivity. We conclude that social housing of pygmy slow lorises improves their well-being by reducing stress levels, and that their group housing in captivity can provide dividends for the conservation of this endangered nocturnal primate because lorises intended for release should find it easier to adapt to natural conditions.

Associations between temperature variations and tourist arrivals: analysis based on Baidu Index of hot-spring tourism in 44 cities in China

Hot-spring tourism refers to entertainment, health preservation, commercial conferences, and other leisure activities at hot-spring locations. This tourism often shows periodic variability, which may be due to seasonal temperature variations. However, studies on the effects of temperature variations on tourist arrivals at hot springs are limited. Therefore, this study aimed to evaluate this relationship in 31 provincial capital cities and 13 s-tier cities in China. Using the Baidu Index, we obtained data for tourist arrivals to hot springs in each city and constructed a generalised additive model to explore the associations between temperature variations and tourist arrivals. We also analysed the statistical significance of the estimated effects during different seasons to explore potential effect modification. A 1 °C increase in temperature was associated with a 1.81% (95% confidence interval (CI): 1.69-1.93) decrease in daily tourist arrivals for hot-spring tourism. Significant positive associations between the abovementioned factors were observed in summer (2.18% change, 95% CI: 1.32-3.04). The effect of temperature on the volume of tourist arrivals may last for approximately 2 months. Robustness analysis confirmed the data reliability. The results indicate that significant relationships exist between temperature variations and hot-spring tourism arrivals, which vary seasonally. This study has significant implications for travel agencies to effectively manage tourist visits to hot spring locations.

Seasonal drivers of faecal glucocorticoid metabolite concentrations in an African strepsirrhine primate, the thick-tailed greater galago (Otolemur crassicaudatus)

As global non-human primate populations show dramatic declines due to climate change, land transformation and other anthropogenic stressors, it has become imperative to study physiological responses to environmental change in order to understand primate adaptability and enhance species conservation strategies. We examined the effects of seasonality on faecal glucocorticoid metabolite (fGCM) concentrations of free-ranging male and female thick-tailed greater galagos (Otolemur crassicaudatus) in an Afromontane habitat. To do so, we established an enzyme immunoassay (EIA) for monitoring fGCM concentrations in the species using a biological validation. Following this, faecal samples were collected each month over the course of a year from free-ranging males and females situated in the Soutpansberg Mountains, Limpopo, South Africa. Multivariate analyses revealed lactation period was a driver of fGCM levels, whereas sex and food availability mostly influenced seasonal fGCM concentrations in the total population. Thus far, the results of this study show that drivers of fGCM levels, an indication of increased adrenocortical activity, in O. crassicaudatus are numerous and complex within the natural environment. The species may be adapted to such conditions and an extreme change to any one component may result in elevated fGCM levels. This increases our understanding of strepsirrhine primate physiology and offers initial insights into species adaptability to a challenging environment.

Why do people visit primate tourism sites? Investigating macaque tourism in Japan and Indonesia

Primates are popular species in wildlife tourism contexts and provide economic benefits to habitat countries where primate-based tourism activities are a part of the country's tourism economy. Primate tourism runs a broad gamut from safari-like expeditions within remote primate habitats to designated monkey parks and incidental primate tourism. In most forms of primate tourism, primate ecology and behaviour are directly influenced by humans, making these interfaces particularly relevant for examination using the lens of ethnoprimatology. While several studies have assessed the impact of tourism on primates, little is known about people's motivations for observing monkeys for recreational purposes. Here we present two case studies-the Jigokudani Monkey Park, Japan, and the Telaga Warna Nature Recreational Park, Indonesia-where we provide quantitative assessments of people's motivations for visiting managed (monkey parks) and unmanaged (incidental) monkey tourism sites. We further show that management regimes, socio-demographic attributes, previous experience of interactions with macaques, and feeding them play a role in people's desire to visit macaque tourism sites. In Japan, those who had interacted with macaques before were more likely to visit the park to observe macaques clearly and at close quarters. In contrast, respondents in Indonesia were more interested in the recreational opportunities offered by the nature reserve rather than in macaques. However, here too, people who had interacted with macaques earlier were more likely to visit incidental macaque tourist sites for the sole purpose of viewing or interacting with macaques. Almost 50% of the Japanese respondents visited the monkey park due to personal inclinations, while less than 14% of people in Indonesia visited the park of their own volition. Also, over 57% of the Japanese respondents said that visiting monkey parks helped them gain a better understanding of macaque behaviour, whereas only about 26% respondents said likewise in Indonesia. Unlike the Japanese respondents, most of the Indonesian respondents engaged in feeding macaques. These findings suggest that management regimes as well as socio-demographic attributes may influence people's motivations to visit macaque tourism sites.

Association between stress and bilateral symmetrical alopecia in free-ranging Formosan macaques in Mt. Longevity, Taiwan

Since 2013, a high incidence of bilateral symmetrical alopecia has been observed in free-ranging Formosan macaques (Macaca cyclopis) in Mt. Longevity, Taiwan. We hypothesized that stress induces alopecia in this population. To verify our hypothesis, we evaluated the histopathological characteristics of skin biopsy and used a validated enzyme immunoassay (EIA) for fecal glucocorticoid metabolite (FGM) analysis, which act as an indicator of stress experienced by the individual. Follicular densities were lower (2.1-3.0 mm²) in individuals with symmetrical alopecia than in those with normal hair conditions (4.7 mm²). Furthermore, anagen to catagen/telogen ratios were lower in individuals with alopecia (0-1.4) than in those with normal hair (4.0). The histopathological characteristics of alopecia were similar to those of telogen effluvium, which indicates that stress is one of the possible etiologies. On the basis of the analytical and biological validation of EIAs for FGM analysis, 11β-hydroxyetiocholanolone was considered suitable for monitoring adrenocortical activity in both sexes of Formosan macaques. The mean concentrations (standard error; sample size) of 11β-hydroxyetiocholanolone were 2.02 (0.17; n = 10) and 1.41 (0.10; n = 31) μg/g for individuals with and without alopecia, respectively. Furthermore, the results of logistic regression analysis show that 11β-hydroxyetiocholanolone (p = 0.012) concentration was positively associated with alopecia. Thus, stress was the most likely to trigger symmetrical alopecia in Formosan macaques in Mt. Longevity. Although stress can decrease the fitness of an individual, considering the population status of Formosan macaques in Taiwan is stable and alopecia was only observed in our study area, which is isolated from other populations, the impact on the total population of Formosan macaque in Taiwan is limited. Nonetheless, stress-induced immunosuppression and alopecia might affect the local abundance and increase zoonosis risk due to frequent human-macaque contact in Mt. Longevity. Future studies are suggested to focus on the causative factor of stress and the effects of stress and alopecia on the health and welfare in the Formosan macaques.

Do dominant monkeys gain more warmth? Number of physical contacts and spatial positions in huddles for male Japanese macaques in relation to dominance rank

Animals show various forms of behavioral thermoregulation to minimize cold stress. Given that higher dominance rank is often associated with increased fitness in group-living animals, higher-ranking individuals may also benefit from better access to thermally optimal spatial positions within huddles. This study examined the association between dominance rank and the potential thermoregulatory benefits of huddling behavior in Japanese macaques (Macaca fuscata) inhabiting Shodoshima Island, which form exceptionally large huddles. I photographed monkey huddles, and analyzed the number of individuals that males were in contact with and males' spatial positons in huddles. Higher-ranking males were significantly more likely to be in contact with larger numbers of individuals in huddles. Higher-ranking males occupied non-peripheral positions in huddles more often than lower-ranking males, which put them in contact with larger numbers of individuals. These results suggest that high dominance rank may confer potential thermal advantages on male Japanese macaques. The mechanism for this is likely that the highest-ranking male often intrude in already-formed huddles, although such behaviors of males were not quantitatively assessed. This study contributes to a better understanding of the mechanisms of cold adaptation in relation to dominance rank in group-living animals.

Ambient temperature and intentional homicide: A multi-city case-crossover study in the US

BACKGROUND

There has been an increasing interest in the association between ambient temperature and violence and crime, in the context of global warming. We aimed to evaluate the association between daily ambient temperature and intentional homicide-a proxy for overall inter-personal violence.

METHODS

We collected daily weather and crime data from 9 large US cities (Chicago, Detroit, Fort Worth, Kansas City, Los Angeles, Louisville, New York, Tucson and Virginia Beach) from 2007 to 2017. A time-stratified case-crossover design was used. The associations were quantified by conditional logistic regression with distributed lag models, adjusting for relative humidity, precipitation and effects of public holidays. City-specific odds ratios (OR) were used to calculate the attributable fractions in each city.

RESULTS

Based on 19,523 intentional homicide cases, we found a linear temperature-homicide association. Every 5 °C increase in daily mean temperature was associated with a 9.5% [95% confidence interval (CI): 4.3-15.0%] and 8.8% (95% CI: 1.5-16.6%) increase in intentional homicide over lag 0-7 days in Chicago and New York, respectively. The association was not statistically significant in the other seven cities and seemed to be stronger for cases that happened during the hot season, at night (18:00-06:00) and on the street. During the study period, 8.7% (95%CI: 4.3-12.7%) and 7.1% (95% CI: 1.4-12.0%) intentional homicide cases could be attributed to temperatures above city-specific median temperatures, corresponding to 488 and 316 excess cases in Chicago and New York, respectively.

CONCLUSIONS

Our study suggests that the interpersonal violence might increase with temperature in some US cities. We also provide some insights into the mechanisms and targeted prevention strategies for heat-related violence.

Climate induced stress and mortality in vervet monkeys

As the effects of global climate change become more apparent, animal species will become increasingly affected by extreme climate and its effect on the environment. There is a pressing need to understand animal physiological and behavioural responses to climatic stressors. We used the reactive scope model as a framework to investigate the influence of drought conditions on vervet monkey (Chlorocebus pygerythrus) behaviour, physiological stress and survival across 2.5 years in South Africa. Data were collected on climatic, environmental and behavioural variables and physiological stress via faecal glucocorticoid metabolites (fGCMs). There was a meaningful interaction between water availability and resource abundance: when food availability was high but standing water was unavailable, fGCM concentrations were higher compared to when food was abundant and water was available. Vervet monkeys adapted their behaviour during a drought period by spending a greater proportion of time resting at the expense of feeding, moving and social behaviour. As food availability decreased, vervet mortality increased. Peak mortality occurred when food availability was at its lowest and there was no standing water. A survival analysis revealed that higher fGCM concentrations were associated with an increased probability of mortality. Our results suggest that with continued climate change, the increasing prevalence of drought will negatively affect vervet abundance and distribution in our population. Our study contributes to knowledge of the limits and scope of behavioural and physiological plasticity among vervet monkeys in the face of rapid environmental change.

Changes in social behavior and fecal glucocorticoids in a Japanese macaque (Macaca fuscata) carrying her dead infant

Maternal care towards dead infants has been observed in many wild and captive mammals, but the consequences of this behavior for social interactions and the physiological status of the mother remain elusive. Here, we report changes in rates of aggression and grooming time, and fecal glucocorticoid (fGC) levels in a free-ranging female Japanese macaque (Macaca fuscata) that carried her dead infant for 20 days. Our observations revealed that when carrying the dead infant, the mother showed increased rates of grimace, avoidance, and human-directed behaviors, along with reduced allogrooming time and fleeing from other individuals. Postpartum fGC levels were comparable to those of non-pregnant and non-lactating females, suggesting that the energetic costs and stress of carrying a dead infant are low. Our findings indicate that carrying a dead neonate can have three profound consequences on the mother: increased fearful behavior, decreased allogrooming, and a rapid return to baseline fGC levels. We hypothesize that dead infant-carrying may have evolved as a strategy to mitigate stress from infant loss. These findings have implications for our understanding of grief in nonhuman primates and can impact management protocols surrounding deaths in captive social groups.

On the sunny side of (new) life: Effect of sunshine duration on age at first reproduction in Japanese macaques (Macaca fuscata)

To produce offspring early in life is energetically demanding and depends greatly on environmental conditions. In female primates, age at first reproduction (AFR) has been associated with social parameters (e.g., population density and social rank), food availability and meteorological conditions (e.g., photoperiod, rainfall patterns, and temperature). Regarding the latter, less attention has been given to the influence of sunshine. In nonhuman primates, including the northern‐most distributed Japanese macaque (Macaca fuscata), sunbathing is an effective thermoregulatory strategy to maintain sufficient energy intake during harsh winter months. Furthermore, the energetic value of sunshine and its role in the synthesis of essential vitamins important for sexual development and overall fertility is well investigated using human and animal models. In the present study, we hypothesized that female's AFR is influenced by the amount of sunshine in a semi‐free‐ranging, provisioned a group of Japanese macaques. To test this, we gathered data on sunshine duration in the year females theoretically experienced the onset of puberty. This phase of the female life cycle is particularly prone to the effects of environmental conditions. In addition to the investigation of sunshine duration and other meteorological conditions (i.e., rainfall and temperature) we controlled for social parameters (i.e., group size and sex ratio) as potential covariates. We found a clear effect of sunshine duration on female AFR: Females who entered puberty in years with more sunshine reproduced for the first time at significantly younger ages than females who experienced less sunshine during this specific period of their development. Possible mechanisms for how the sunshine influences sexual maturation in Japanese macaques are discussed.

We investigated the influence of sunshine during the year of puberty onset on a female's age at first reproduction (AFR).

We used 20 years of birth data from a semi‐free‐ranging group of Japanese macaques and meteorological data provided online by local weather stations

We controlled for the influence of other meteorological conditions as well as for group size and socionomic sex ratio

Higher mean sunshine duration in the year of puberty onset significantly decreased females’ AFR.

Social and ecological factors alter stress physiology of Virunga mountain gorillas (Gorilla beringei beringei)

Living in a rapidly changing environment can alter stress physiology at the population level, with negative impacts on health, reproductive rates, and mortality that may ultimately result in species decline. Small, isolated animal populations where genetic diversity is low are at particular risks, such as endangered Virunga mountain gorillas (Gorilla beringei beringei). Along with climate change-associated environmental shifts that are affecting the entire population, subpopulations of the Virunga gorillas have recently experienced extreme changes in their social environment. As the growing population moves closer to the forest's carrying capacity, the gorillas are coping with rising population density, increased frequencies of interactions between social units, and changing habitat use (e.g., more overlapping home ranges and routine ranging at higher elevations). Using noninvasive monitoring of fecal glucocorticoid metabolites (FGM) on 115 habituated Virunga gorillas, we investigated how social and ecological variation are related to baseline FGM levels, to better understand the adaptive capacity of mountain gorillas and monitor potential physiological indicators of population decline risks. Generalized linear mixed models revealed elevated mean monthly baseline FGM levels in months with higher rainfall and higher mean maximum and minimum temperature, suggesting that Virunga gorillas might be sensitive to predicted warming and rainfall trends involving longer, warmer dry seasons and more concentrated and extreme rainfall occurrences. Exclusive use of smaller home range areas was linked to elevated baseline FGM levels, which may reflect reduced feeding efficiency and increased travel efforts to actively avoid neighboring groups. The potential for additive effects of stress-inducing factors could have short- and long-term impacts on the reproduction, health, and ultimately survival of the Virunga gorilla population. The ongoing effects of environmental changes and population dynamics must be closely monitored and used to develop effective long-term conservation strategies that can help address these risk factors.