Virginia Landau, Jessie Grenfell, Erica Metelovski and James E. King,
The Jane Goodall Institute and the University of Arizona

Chimpanzees have been exotic attractions for curious people visiting zoos for nearly 100 years. During that time, housing and husbandry methods for chimpanzees have changed from barren cages to glass and concrete enclosures to modern attempts to replicate the natural environment of chimpanzees. Changes in the methods of daily care and improved medical techniques have accompanied advancements in housing.

A study was designed to determine the extent to which improved housing and husbandry techniques have increased the longevity of chimpanzees over the last 55 years. Survival data on 749 chimpanzees were extracted from the Chimpanzoo database and analyzed by the product limit survival procedure. The analysis showed markedly longer survival times for chimpanzees born after 1940 than for those born before 1940. Mortality during the first year of life was extremely high both before and after 1940. The form of the survivability function for those more recently born chimpanzees mirrors that for human populations during the middle part of the eighteenth century when medical science contributed virtually nothing to longevity. The vast majority of chimpanzees born after 1940 were born in the past 20 years. Therefore even with improved daily and medical care and more appropriate housing, chimpanzees still show alarmingly high mortality rates after their first year o life. The longevity hazard function showed that the greater likelihood of dying occurred early and late in the Chimppanzee life span. Male mortality was higher than female mortality at all ages independent of year of birth.

Keepers of older chimpanzees believe that the stability of the keeper staff and the environment and presence of a relative or friend were important in prolonging life. Examination of the data showed that the more transfers the chimpanzee experienced the more likely it was to survive. This may be caused by the fact that very old, sick, or depressed chimpanzees are not candidates for transfer or it may be that a new environment increased the probability of a longer life span.

Abstracted from a paper delivered at the 17th Congress of International Primatological Society at the University of Antananarivo, Madagascar.