Behavioral thermoregulation of wild Japanese macaques: comparisons between two subpopulations

Abstract

We studied the behavioral thermoregulation of Japanese macaques in two troops that live in the coniferous (1,000-1,200 m in elevation) and coastal forests (0-200 m in elevation) of Yakushima. Frequency of sunbathing, huddling, and microhabitat selection during inactivity was compared. The difference in mean annual air temperature between the forests was more than 7 degrees C. In both forests, when the weather was clear, macaques spent more time being inactive in the sunshine in winter than in autumn. In winter, they huddled more often when it was clear than when cloudy. Microhabitat selection to stay in the sunshine during winter differed between the two forests. In winter, macaques spent more time inactive in open habitats in the coniferous forest and in the trees in the coastal forest than in autumn, respectively. This difference is related to the lower crown height in the coastal forest and the large open habitats (logged area) available only in the coniferous forest. In winter, skin temperature measured by temperature-sensitive transmitters was 1.32-1.71 degrees C higher when sunbathing, and 0.83-4.75 degrees C higher when huddling than staying in the shade without huddling. In winter, the proportion with which they stayed in the sunshine or huddled in winter did not differ between the two forests, in spite of the difference in air temperature. This suggests that Japanese macaques respond to seasonal changes in air temperature, not the absolute temperature, and that they acclimatize themselves to thermal conditions that require behavioral thermoregulation only during the season when thermoregulation is most costly.

Communicative and Cognitive Underpinnings of Animal Group Movement

“…Finally, behavioural thermoregulation may favour group living, as huddling together to conserve energy and share body heat during cold periods can be an advantage. This applies mainly to small-bodied species and appears to be relevant only for a small number of primate species (Hanya et al 2007;Ostner 2002).…”

Shape of, and body direction in, huddles of Japanese macaques (Macaca fuscata) in Arashiyama, Japan

“…Because air temperatures are lower at night and diurnal primates have reduced body heat during the night (Honnebier et al 1992), these animals often huddle from evening until the next morning (Vessey 1973;Anderson and McGrew 1984;Ansorge et al 1992;Wada et al 2007). Moreover, some primate species rest in group huddles during daytime (Dunbar and Nathan 1972;Hanya et al 2007;Zhang and Watanabe 2007).…”

“…They huddle with other individuals for thermoregulation both in daytime and at night in winter (Yasuda 1996;Takahashi 1997;Hanya et al 2007;Wada et al 2007). Their huddles consist of 2, 3, or more individuals (Yasuda 1996;Zhang and Watanabe 2007), and are frequently composed of maternal kin-related females (Takahashi 1997;Wada et al 2007).…”

“…Some primates conserve body heat via physical contact when the air is cold (Anderson 1998;Hanya et al 2007;Wada et al 2007). Because air temperatures are lower at night and diurnal primates have reduced body heat during the night (Honnebier et al 1992), these animals often huddle from evening until the next morning (Vessey 1973;Anderson and McGrew 1984;Ansorge et al 1992;Wada et al 2007).…”

Preface to the special contribution “Out of the tropics: ecology of temperate primates”

“…Therefore, it is expected that these species exhibit a variety of adaptations that help them to cope with the ecological demands associated with living in marginal temperate habitats. Temperate-living primates are not necessarily less studied than tropical-living ones; for example, Japanese macaques have been studied at many study sites in the Japanese Archipelago for more than 60 years (Nakagawa et al 2010), and their unique adaptations to coldness and strong seasonality, which are key characteristics of temperate habitats, have been well documented (Hori et al 1977;Hanya 2004;Hanya et al 2007). However, there have been few attempts to relate these findings to studies in tropical areas and to generalize the characteristics of temperate forests and the ecological strategies of primates that live there.…”