The Japanese macaque is diurnal, variably spending the daytime foraging, travelling, socially interacting and resting. It is an unfussy eater and its diet varies with habitat and season (7). Typically, it feeds on leaves, fruit, berries, seeds, small animals, insects and even fungi (1) (7).
As with all species of macaque, the Japanese macaque lives in large social groups known as ‘troops’ (8). Group size can vary greatly, with an average troop containing around 41 individuals (7). Troops that are provisioned with extra food have been known to reach as many as 700 individuals (5). Within the troop, the females are maternally related, while male Japanese macaques transfer between troops (9). There is a strict dominance hierarchy, with lower ranking individuals having less access to resources such as food (10). A young female macaque inherits its mother’s rank, and is also dominant to its younger siblings (11).
In the Yakushima Island subspecies (Macaca fuscata yakui), the breeding season begins in September and lasts until February (9). The male competes for access to receptive females, with higher ranking males gaining more mating opportunities (9). The female is usually reproductively active between the ages of 6 and 18 years of age, and will mate with an average of 10 males during the breeding season, continuing to mate even after conception (4) (5) (9). The gestation period for the Japanese macaque is around 173 days, after which a single infant is usually born, though twins are not unheard of (5) (12).
With its thick coat, the Japanese macaque can survive winter temperatures of -15 degrees Celsius. However, it is probably most well known for its habit of sitting in natural hot springs in order to escape the winter extremes (4) (7). Japanese macaques are also thought to display ‘culture’, where a learned behaviour is passed through the troop (11). The most famous example of this is where a young female in a provisioned troop began washing potatoes and wheat in sea water. This behaviour was transmitted to other members of the troop and has since been passed on to subsequent generations (11).