Abstract

Mammals use thermoregulatory behaviors to maintain optimal body temperatures when facing variable weather conditions. During cold temperatures, these behaviors can serve as an energetically inexpensive way to modulate heat loss. We assessed the use of thermoregulatory behaviors in a semi free-ranging group of Japanese macaques (Macaca fuscata) in Inuyama, Japan during winter. We recorded activity, body postures, and sun exposure for five animals (N=443 observation hrs) exposed to natural thermal variation (-2.9°C to 10.8°C). Air temperature and solar radiation were recorded via an on-site weather station. At colder temperatures, macaques utilized heat-conserving body postures more frequently, engaged in longer periods of physical contact, and spent less time moving. Additionally, when daytime solar radiation was high, macaques rested in sunny locations more frequently than shady locations. These results are consistent with a strategy to behaviorally conserve heat loss. Decreases in movement at cold temperatures further suggest that animals are attempting to reduce energy expenditure when thermoregulatory costs are highest. In sum, these results indicate that Japanese macaques utilize heat- and energy-conserving behaviors as part of their thermoregulatory repertoire when experiencing cold temperatures in winter.