The effects of food sources on Japanese monkey home range size and location, and population dynamics

The effects of supplemental feeding by tourists on wild Japanese monkey's home range size and location, and troop size and composition were studied for two monkey troops, Troop A and Troop B, living along the Irohazaka loop road, Nikko National Park, central Japan. Changes were documented based on data gathered from 1982 to 1996 by the use of radio telemetry. Troop A's home range size shrank and changed from separate winter and summer ranges to a single, year-round home range, with its core located in a high elevation area where supplemental feeding by tourists was heavy. Troop B's home range also shrank and shifted to a lower elevation where supplemental feeding by tourists was heavy. Troop A's population size increased between the winters of 1983–1984 and 1990–1991 in conjunction with an increase in human encounter rates, and then decreased. Troop B's size increased until the winter of 1993–1994, and then decreased. The instability of troop size between 1993 and 1996 may be explained by documented factors such as a decrease in the adult sex ratio, an increase in the infant-female ratio, and an increase in juvenile mortality and/or emigration, all of which may have been influenced by supplemental feeding by tourists.