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

Abstract

The ability of animals to survive dramatic climates depends on their physiology, morphology and behaviour, but is often influenced by the configuration of their habitat. Along with autonomic responses, thermoregulatory behaviours, including postural adjustments, social aggregation, and use of trees for shelter, help individuals maintain homeostasis across climate variations. Japanese macaques (Macaca fuscata) are the world's most northerly species of nonhuman primates and have adapted to extremely cold environments. Given that thermoregulatory stress can increase glucocorticoid concentrations in primates, we hypothesized that by using an available hot spring, Japanese macaques could gain protection against weather-induced cold stress during winter. We studied 12 adult female Japanese macaques living in Jigokudani Monkey Park, Japan, during the spring birth season (April to June) and winter mating season (October to December). We collected faecal samples for determination of faecal glucocorticoid (fGC) metabolite concentrations by enzyme immunoassay, as well as behavioural data to determine time spent in the hot springs, dominance rank, aggression rates, and affiliative behaviours. We used nonparametric statistics to examine seasonal changes in hot spring bathing, and the relationship between rank and air temperature on hot spring bathing. We used general linear mixed-effect models to examine factors impacting hormone concentrations. We found that Japanese macaques use hot spring bathing for thermoregulation during the winter. In the studied troop, the single hot spring is a restricted resource favoured by dominant females. High social rank had both costs and benefits: dominant females sustained high fGC levels, which were associated with high aggression rates in winter, but benefited by priority of access to the hot spring, which was associated with low fGC concentrations and therefore might help reduce energy expenditure and subsequent body heat loss. This unique habit of hot spring bathing by Japanese macaques illustrates how behavioural flexibility can help counter cold climate stress, with likely implications for reproduction and survival.

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

“…Thus, reduced energy intake on rainy days is unlikely to explain elevated baseline FGM levels, as has been shown in food‐deprived humans (Tomiyama et al, ) and birds (Kitaysky, ; Kitaysky, Piatt, Wingfield, & Romano, ). However, huddling during rain may also function as thermoregulatory behavior (Watts, ), similar to Japanese macaques ( Macaca fuscata ) using hot spring bathing to counter cold stress during the winter (Takeshita, Bercovitch, Kinoshita, & Huffman, ). Resumption of feeding during heavy or prolonged rain might therefore increase allostatic load, as the gorillas work harder to maintain a stable body temperature (McEwen & Wingfield, ; Romero, ).…”

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

“…Due to their despotic social system and their northern distribution, Japanese macaques have to cope with both cold and social stress particularly during the mating season, which occurs in fall and winter. A recent study on female Japanese macaques in the Jigokudani Monkey Park reported that bathing in thermal hot springs is an alternative thermoregulatory strategy in this particular group (Takeshita, Bercovitch, Kinoshita, & Huffman, ): The direct heat of the hot water is a physiological benefit because it significantly reduces the glucocorticoid levels of female monkeys. A stress‐induced increase in glucocorticoid levels in different animal species including macaques impairs the secretion of sexual hormones (e.g., GnRH, luteinizing hormone [LH], estrogen) important for sexual maturation and cycling (Hayashi & Moberg, ; Oakley et al, , Rivier & Rivest, ).…”

Hot-spring bathing of wild monkeys in Shiga-Heights: origin and propagation of a cultural behavior

“…Therefore, they inferred that the behavior helps with thermoregulation. Sayuri Takeshita and her colleagues (Takeshita et al 2018) showed that hot-spring bathing has a stress reduction effect in adult females (Fig. 3).…”

“…4 The monkeys of Jigokudani in the hot spring. Takeshita et al (2018) reported the stress-reduction effect of hot-bathing in addition to thermoregulation (photo by Toshio Hagiwara) Fig. 5 Japanese monkeys in Jigokudani.…”