Estimation of abundance and distribution of Japanese macaques using track counts in snow

Abstract

We introduced a technique based on groundbased track counts in snow for simultaneously estimating the abundance and distribution of Japanese macaques Macaca fuscata (Blyth, 1875) and evaluated its efficiency by conducting a field trial in northern Japan. Within the 50-km 2 area, we selected five transects with consideration of the spatial distribution of vegetation, local climate, and geographical conditions contained in the entire area. Five trained researchers recorded the track counts three times in those geolocations that intersected with each transect. We estimated the macaque abundance by the line-intercept sampling (LIS) technique using the number of tracks and predicted its distribution by ecological-niche factor analysis (ENFA) using the tracks as a proof of macaques' presence. We confirmed that the LIS-based technique could yield reasonably accurate estimates of the number of individuals and troops, compared with the population estimates of macaques based on the home-range method. We successfully used ENFA in constructing a macaque distribution model that had a high predictive performance; this was verified by comparing the predicted macaque distribution with the actual use of habitat obtained by tracking radiotagged troops in the study area.

Influence of Heavy Snow on the Feeding Behavior of Japanese Macaques (Macaca Fuscata) in Northern Japan

“…). This observation is in accordance with those of previous studies conducted in the same study area [Enari & Sakamaki, ; Sakamaki & Enari, ]. Taken together, these findings indicate that winter‐feeding‐site use by Japanese macaques in heavy snow conditions becomes more restricted by the distribution of refuges within their range than by the abundance and distribution of food resources.…”

“…The Japanese macaques inhabiting the Shirakami Mountains constitute the largest population in northern Japan [Biodiversity Center of Japan, ; Enari & Suzuki, ]. In March 2008, the individual and troop densities in and around the study area were determined to be 5.19 individuals/km 2 (including non‐troop males) and 0.15 troops/km 2 , respectively [Enari & Sakamaki, ]. Meanwhile, the mean troop size (which we constantly monitored in the study area) was approximately 35 individuals ( N = 4).…”

“…We investigated 145 segments in 2008, 243 segments in 2009, 128 segments in 2010, and 247 segments in 2012. We determined the segment length based on the spatial distribution of macaque individuals within a troop during snowy seasons in the study area [Enari & Sakamaki, ]. To reduce complexity, we classified all foraged plant species according to plant type (vine, shrub, and tree) and shade tolerance (shade‐tolerant, intermediary, and shade‐intolerant), as outlined by the Forest Development Technological Institute [].…”

“…Snow also restricts macaques from traveling on the ground [Izumiyama, ; Watanuki & Nakayama, ], leading to a reduction in their winter range, which is less than half the size of their range during other seasons [Enari et al, ; Imaki et al, ; Koganezawa & Imaki, ; Wada & Ichiki, ]. In addition, macaques aggregate on southern slopes at low altitudes (e.g., <300‐m above sea level in the Shirakami Mountains) to prevent exposure to severe cold [Enari & Sakamaki, ; Sakamaki & Enari, ]. Besides these behavioral constraints, snow cover affects diet.…”

Impact assessment of dam construction and forest management for Japanese macaque habitats in snowy areas

“…Next, we prepared raster maps with the same resolution, showing 13 environmental predictors that potentially explained the distribution of the presence sites (Table ). We selected those predictors on the basis of the following assumptions on habitat use by macaques in snowy regions: (1) their habitat use is fundamentally sensitive to food resources, which are related to forest cover type, maturation stage of forests [Sakamaki & Enari, ; Sakamaki et al, ], and land use (such as distribution of forest edges) [Imaki et al, ]; (2) the distribution of refuges against snowstorms, which is determined by topography (such as elevation and terrain conditions) and the distribution of evergreen conifers, strongly limits macaque occurrence during winter [Enari & Sakamaki, ; Sakamaki & Enari, ]. Of the 13 predictors, the five describing forest cover types were calculated from National and Private Forest Planning Maps (analog maps, reduction scale = 1/5,000), provided by the Japanese Forest Agency and the Aomori Prefectural Government.…”