A bioeconomic study on a provisioned troop of Japanese monkeys (Macaca fuscata fuscata) at koshima islet, Miyazaki

Abstract

The natural and provisioned (wheat) food intake of the Japanese monkeys on Koshima was measured by direct observation. It was found that the portion of wheat consumed reflects such social structures in Japanese monkeys as (a) the structure of cocentric circles composed of several classes, (b) female ranking orders, (c) social strictness in breeding or non-breeding seasons.

The natural food intake forIcho (2–3 years old female) was estimated for three seasons (April, September and December) during 1971. Her daily caloric intake was estimated from a quantitative list of natural foods eaten and the quantity of wheat eaten by multiplying the appropriate caloric values, and digestibility of 70%. The kcal day per values were 411 in spring, 522 in summer and 559 in winter. Her daily energy consumption (DEC) was estimated to be 398, 423, and 447 kcal/day in the respective seasons derived from the equation DEC =153W^2/3 which was obtained from data on activity telemetry and basal metabolic rates. The two spring values are in agreement. The summer and winter values show considerable differences.

The dependency on wheat was calculated for individuals of various ages and sexes. The dependency of juveniles (60%) is about double that of ordinary females (25%).

The Koshima troop is largely dependent on the evergreen broad leaves through all seasons.

The increase of the number of females was cumulatively simulated assuming constant age-specific fecundity and mortality. There appeared one stagnated period of increase during the years 1961–1964 due to external factors. It will be a future problem to relate the quality of nutrition to reproductive performance.