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

We introduced a technique based on ground-based 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-km2 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 radio-tagged troops in the study area.