Massive Destruction of Symphonia globulifera (Clusiaceae) Flowers by Central American Spider Monkeys (Ateles geoffroyi)1

Although more than 39 primate species have been described as nectar feeders, no studies have documented the negative affect this behavior may have on the reproductive success of the plants they consume. Here we report, for the first time, massive flower destruction of the tropical tree Symphonia globulifera by the frugivorous spider monkey, Ateles geoffroyi, and document the detrimental effect this behavior has on fruit set. Foraging behavior was collected from one troop of A. geoffroyi during 460 contact hours from June 1999 to May 2000 in the tropical humid forest at the Refugio de Vida Silvestre Punta Rio Claro (8°39′N, 83°44′E) in the Osa Peninsula in Southwestern Costa Rica. Detailed phenological data were collected from ten S. globulifera trees that the monkeys fed upon and ten trees that were outside of their home range, but in the Refugio. From July to September 1999 S. globulifera was the most important species consumed, representing from 86 to 100 percent of the total feeding time each month. Monkey foraging on S. globulifera flowers was destructive, detaching the flowers completely from the branches in 80 percent of the foraging bouts, and leaving flowers without petals and with damaged reproductive parts in 20 percent of the bouts. None of the ten trees where the monkeys were foraging set fruit, but seven of ten trees outside of their home range set fruit in November and December 1999. These results suggest that some primates may play an important role in floral herbivory in tropical forests and the subsequent reduction in reproductive success. Future studies should focus on evaluating the long‐term effect this foraging behavior may have on the population structure of this species and evaluate the effect of primate floral herbivory on the reproductive success of other plant species.