Student Prize Award Abstract
1995 Oral Paper Award

REDTAIL MONKEYS AND STRYCHNOS MITIS: A PLANT-ANIMAL INTERACTION IN THE KIBALE FOREST, UGANDA.

J. Lambert
Department of Anthropology, University of Illinois, Urbana, IL 61801

The feeding behavior of a group of 28 redtail monkeys (Cercopithecus ascanius schmidtii) was observed from June 1993 to April 1994 in the Kibale Forest of western Uganda. This group fed extensively on the ripe fruits of Strychnos mitis during September and October, 1993. The monkeys consumed fruits at a rate of approximately 2 per minute and almost always spat out intact seeds under the crown of the parent tree. This study reports results of an experiment designed to test the influence of monkey feeding on seed fate of S. mitis. The fate of seeds processed by redtails versus the fate of fruit that had fallen naturally from the tree were monitored for 6 months (n=180). Seeds clearly benefited from monkey processing. Eighty-three percent of seeds spat out by redtails germinated, while only 12% of the unprocessed fruits survived to germination (df=1; X²=91.20; p<0.001). Of the processed seeds that germinated, 60% survived to seedling establishment, while only 5% of unprocessed fruits survived to seedling establishment (df=1; X²=605.388; p<0.001). Unprocessed fruits were also more likely to be attacked and damaged by seed predators (df=1; X²=11.768; p<0.001) and fungal pathogens (df=1; X²=156.88; p<0.001). Finally, the seed shadow created by the redtails is similar to the extant distribution of S. mitis in Kibale, where these trees are typically found in fairly dense groves. The data indicate that redtail monkeys are influential in the reproduction of this tropical tree species and may thus be important agents in Kibale Forest regeneration.