The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


Prey Switching by Chimpanzees at Ngogo, Kibale National Park

DAVID P. WATTS1 and JOHN C. MITANI.

1Anthropology, Yale University, 2Anthropology, University of Michigan

March 26, 2015 9:45, Grand Ballroom E/F/G Add to calendar

Chimpanzees (Pan troglodytes) prey on multiple vertebrates, but particularly target sympatric red colobus monkeys (Piliocolobus spp.). Heavy predation at Ngogo has caused a local red colobus population decline. Chimpanzees are mostly secondary consumers and prey availability should not affect their density, but meat’s nutritional value makes continued hunting worthwhile.

We investigated whether the chimpanzees increasingly hunted major alternative prey -- redtail monkeys (Cercopithecus ascanius), grey-cheeked mangabeys (Lophocebus albigena), and guerezas (Colobus guereza) – as red colobus availability declined. We confirmed earlier reports that encounters with red colobus, but not redtails or mangabeys, have declined, as have red colobus hunting and harvest rates. Guereza encounters (uncommon) have also declined. The likelihood of hunting alternative prey on encounter has increased over time and as encounters with red colobus have decreased (logistic regression). Elapsed time and variation in red colobus offtake together explain 15% of the variance in the rate of hunting alternative prey (multiple regression with robust SEs; p = 0.018). Consequently, alternative prey have contributed increasing proportions of total offtake. However, hunts of redtails and mangabeys are still rare despite high densities of both, and success rates and the mean number of kills per successful hunt are lower than for red colobus hunts. While the overall rate at which the chimpanzees hunt these four species combined has not declined significantly, the harvest rate has decreased. The rate at which the chimpanzees hunt red colobus on encounter has not decreased; thus predation pressure on red colobus is still high.

NSF (SBR-925-3590, BCS-0215622, IOB-0516644), The L.S.B. Leakey Foundation; The National Geographic Society; Yale University; University of Michigan.