Predicting Capacity Demand on Sanctuaries for African Chimpanzees (Pan troglodytes)

Wildlife sanctuaries rescue, rehabilitate, reintroduce, and provide life-long care for orphaned and injured animals. Understanding a sanctuary's patterns in arrival, mortality, and projected changes in population size can help managers plan carefully for future needs, as well as illuminate patterns in source populations of wildlife. We studied these dynamics for chimpanzees (Pan troglodytes) in 11 sanctuaries of the Pan African Sanctuary Alliance (PASA). We analyzed historic demographic patterns and projected future population dynamics using an individual-based demographic model. From 2000 to 2006, the population in these sanctuaries has been growing at a rate of 15% per year. This growth is driven by arrivals of new individuals, with an average of 56 arrivals per year. The median age of the 760 chimpanzees living in these sanctuaries as of 2007 was 9 yr, with 76% of the population < 15 yr. We found no significant difference in survivorship to age 20 between these chimpanzees and those maintained in North American accredited zoos. The size of the population in 20 yr is projected to be between 550 and 1800, depending on different assumptions about arrival and reintroduction rates. Projected shifts in age structure, including increases in the proportions of adolescent (9-19 yr of age) and older (35+) chimpanzees, may necessitate adjustments to management, veterinary care, and housing. This research illustrates how data on historic population dynamics can be modeled to inform future sanctuary capacity and management needs, allowing sanctuaries to plan better for their populations' long-term care.