Aggressive Response of Japanese Macaques toward a Japanese Giant Flying Squirrel

Abstract

We observed 4 cases of aggressive response of Japanese macaques (Macaca fuscata) toward a Japanese giant flying squirrel (Petaurista leucogenys) at the feeding site of the Katsuyama group. When a Japanese giant flying squirrel glided over to a tree at the feeding site, almost all the adult and subadult monkeys resting around the tree mobbed the flying squirrel with threatening sounds. Immature monkeys aged ≤ 2 years screamed, and the mothers retrieved their infants immediately on spotting the flying squirrel. Several peculiar high-rank adult males and females chased, threatened, and attacked the flying squirrel for 25-114 minutes, but mothers with infants seldom approached the flying squirrel. High-ranking adult males had a greater tendency to perform agonistic displays toward the flying squirrel than low-ranking adult males and females. Our observation and previous reports about interspecific encounters suggest that Japanese macaques recognize the Japanese giant flying squirrel as being in the same category as raptors, which prey on Japanese macaques. This explains why the monkeys respond aggressively, which is typical of antipredator behavior, to the common behavioral features of the flying squirrel and raptor-gliding and descending nearby. However, this aggressive response does not seem to benefit monkeys in terms of avoiding predators because the flying squirrel is not actually a predator. There are 2 other possible benefits. Their sensitivity to behavioral features that resemble those of the raptors may improve their efficiency in terms of antipredator behavior towards actual predators such as raptors. In addition, adult or subadult male monkeys may display their fitness to potential mates by performing agonistic displays in response to the Japanese giant flying squirrel. In order to better understand the relationship between Japanese macaques and other species, it is necessary to establish a system for collecting and sharing data on rarely observed cases.