Social Interactions Between Rhesus Macaques ( Macaca mulatta) and Assamese Macaques ( M. assamensis) in Nepal: Why Do Male Rhesus Macaques Follow Social Groups of Assamese Macaques?

Abstract

Although the majority of primates inhabit tropical and subtropical regions, several groups have expanded their habitats into temperate regions (Fleagle, 1999). One such species is the Japanese macaque (Macaca fuscata), the northernmost-dwelling non-human primate species, which inhabits even heavily snowy areas such as Mt. Hakusan (Hayashi, 1969), Kurobe Gorge (Akaza, 2002), Shiga Heights (Wada & Tokida, 1981), Kamikochi Basin (Izumiyama, 2014), Nikko (Koganezawa & Imaki, 1999), Shirakami Mountains (Enari & Sakamaki-Enari, 2013), and Shimokita Peninsula (Watanuki et al., 1994). To survive in such harsh environments, macaques have evolved unique morphological (Inagaki & Hamada, 1985; Hamada, 2002) and physiological traits (Hayama et al., 1998). In addition, several behaviors for avoiding the cold during winter have been reported, such as huddling (Takahashi, 1997; Hayashi & Mizuno, 2011), the use of ledges on steep cliffs (Hayashi, 1969), snow cornices and coniferous forest (Wada & Tokida, 1981; Shitaka, 1984ab; Tarouda, 2002; Izumiyama, 2012) as sleeping sites, and remaining close to a warm water supply pipe from a hot spring (Akaza, 1987). Furthermore, we previously reported that the macaques in Kurobe Gorge use caves as a snow/wind shelter during mid-winter (Kashiwagi et al., 2012; Kashiwagi and Takai, 2017). Most natural caves develop in limestone and are found exclusively in karst areas. For example the Saru-ana Cave, which is known to be used by Japanese macaques, is a natural limestone cave in the Kanetsuri area along Kurobe Gorge (Kashiwagi et al., 2012). In contrast, artificial caves, such as mines, tunnels, air raid shelters, and other man-made subterraneous openings, can be found all over Japan regardless of geology. Recently, Kashiwagi and Takai (2017) briefly reported that Japanese macaques use an artificial tunnel excavated for warm water supply pipes in granite rocks. However, a detailed report has not yet been published. We recently discovered a copious amount of macaque feces within an abandoned mine, which is a representative artificial cave, in the Nokado area, Nikko City, Tochigi Prefecture, central Japan. This area is mainly underlain by non-karstic rocks, so caves which Japanese macaques can use in this area are restricted to artificial caves. Thus this case study provides reliable data supporting that macaques use artificial caves in addition to natural caves. In this paper, we describe fecal distribution within the abandoned mine and the fecal contents, which we used to estimate the season when the macaques used the cave. The accumulation of case studies such as this will further our understanding of the behavioral strategies that have enabled macaques to overcome severe winters and to expand their range to northern or colder regions.