Infant mortality in mother-reared captive chimpanzees at Taronga Zoo,Sydney

Infant mortality in mother-reared chimpanzees was examined from the records of Taronga Zoo, Sydney, Australia. Sex-specific mortality probabilities were calculated using standard demographic techniques. Male mortality was found to be considerably higher than female mortality. Using the same techniques, changes in infant mortality over time were calculated, with particular reference to changes that had occurred since the chimpanzees were transferred to a new open air enclosure in 1980. Mortality was found to have decreased dramatically since the move to the new enclosure, but the observed decline was exaggerated by the very high proportion of female infants. The main causes of infant death as ascertained from the zoo records were pneumonia and trauma. In addition, undetermined causes in the first day of life were numerous. An examination of the contexts of infanticide in wild and captive chimpanzees revealed slight differences, but factors such as aggression towards unfamiliar individuals and redirected aggression were common to both. Cannibalism in the zoo has so far been limited to the bodies of stillborn infants.