Abstract
The number of Japanese macaques (Macaca fuscata) has rapidly increased under artificially provisioned conditions. At Takasakiyama it increased by 6.9 times during 22 years from 1953 to 1975 when food was given at 618kcal/day/head on average. To control the population growth, provisioning was decreased to 334kcal/day/head from 1975, after which, it increased only by 1.2 times for 19 years until 1994. Destruction of the forest from the increased number of monkeys has continued, however, through eating fruits, shoots and young leaves of the main food trees. Yearly consumption effeciency of monkeys in the forest for 1990 was calculated as 8.7%, which is near to the African elephant. As a result, the vegetation type is changing from that of natural forest. Computer simulation revealed if the population decreases to 60% of its current size and 282kcal/day/head of artificial food is given, consumption efficiency will decrease to 5.8% and the population can be kept almost stable. Further manipulation of the monkey population is necessary at present by altering mortality, natality or both. Supply of many free-ranging monkeys to biomedical experiments should not be recommended from the stance of animal welfare and the quality of experimental animals. On the other hand, temporary birth-control of each cycling female is to be considered. The principle of population control is to keep population parameters at about the level of the natural condition.
