Introduction of chimpanzees onto Rubondo Island National Park, Tanzania

Summary

Rubondo Island, a 240 square kilometre national park in Tanzania's Lake Victoria, had never held wild chimpanzees until the Frankfurt Zoological Society released 17 European zoo-born chimpanzees there in four introductions between 1966 and 1969, nine females and eight males aged four to twelve, most with little prior social integration and some with a history of aggression toward humans. Provisioning was stopped after only two months once the chimpanzees began feeding themselves on bananas, leaves, fruit, and seeds, and the island's lack of predators and abundant year-round liana fruit allowed them to survive largely without human support. The first Rubondo-born infants appeared in 1968; by the 1978 to 1984 monitoring period researchers estimated around 20 individuals, and by 2008 the semi-habituated population had grown to roughly 35 or more. Long-term study since 2000 by an international research team has documented ranging and home range sizes larger than at any other studied chimpanzee site, a comparable parasite profile to mainland populations with three newly recorded nematode species, and this remains the first long-term documentation of chimpanzee introduction outcomes. Difficulties included early aggressive incidents requiring intervention, low habituation limiting behavioral data collection, and the island's remoteness. The project rated itself Successful, citing complete independence from human assistance, ongoing reproduction and population growth, and a highly suitable release environment.