MODELING MANAGED MONKEY POPULATIONS - SUSTAINABLE HARVEST OF LONGTAILED MACAQUES ON A NATURAL HABITAT ISLAND

Computer simulation of population dynamics can be useful in managing h arvested populations of monkeys on islands. Between 1988 and 1991, 420 adult female and 58 adult male simian retrovirus-free Macaca fascicul aris were released onto Tinjil Island, Indonesia, to provide the nucle us for a free-ranging breeding colony. Natural habitat breeding facili ties are excellent alternatives to wild trapping and compound breeding , maximizing the health and well-being of animals destined for essenti al biomedical research. To avoid a population crash, the number of off spring that can be harvested annually must be based on life table char acteristics such as age-specific natality and mortality. We used a mod ified Leslie matrix to model changes in female population size over 26 years. First, we assumed that all 420 females were released simultane ously and varied the annual birth rate (50%, 60%, 70%), survival rate, and number of offspring harvested per year. Assuming high survival an d birth rates vs. low rates, about four times as many female offspring could be harvested annually from a stable population (87 vs. 20 offsp ring). Terminal population size after 26 years did not differ much acr oss rates modeled (568-696 females). Second, we modeled the number of females actually released (including the recent addition of 42 new fem ale breeders) and harvested (averaging 49 annually 1991-1994), and pro jected the population through 2014. This indicated that threshold harv est rates and terminal population sizes increased considerably over th e first model, assuming intermediate (78 harvested, 952 females) and h igh (152 harvested, 1,331 females) rates of survivorship and natality, but were unchanged assuming low rates (20 harvested, 559 females). A review of the literature and held observations on Tinjil suggest that actual birth and survival rates resemble the intermediate values model ed. If so, the present density on the island, projected to be similar to 215 males and females per square kilometer, is approaching carrying capacity. The high values are realistic upper limits. If actual survi vorship and birth rates are at the high end of those modeled, the isla nd's population may be on the verge of rapid expansion, requiring incr eased harvest and provisioning. (C) 1996 Wiley-Liss, Inc.