title: Testing mechanisms of coexistence among two species of frugivorous primates.
abstract: 1. We examined mechanisms of coexistence between two congeneric species of frugivorous primates, the blue monkey (Cercopithecus mitis) and the red-tailed monkey (C. ascanius). 2. We used giving-up densities (the amount of food which animals leave in a patch) in fruit trees to measure foraging efficiency and to evaluate possible mechanisms of coexistence. Animals with higher giving-up densities are less likely to persist in the company of those with lower giving-up densities because the former are not able to exploit food patches used previously by the latter. We climbed trees to estimate giving-up densities by counting the fruit which primates left behind. 3. We tested five possible mechanisms of coexistence. Three mechanisms proposed that each frugivorous species has a lower giving-up density than the other in at least one of the following: (1) different tree species, (2) within-tree foraging zones or (3) seasons. The fourth mechanism predicted that the socially dominant species exploits resources first and that the subordinate species has lower giving-up densities. The final mechanism predicted that one species would find resources more quickly than the other, which would in turn have a lower giving-up density. 4. Four of the five mechanisms received no support from our data. Only a trade-off between interspecific dominance and giving-up densities was supported. 5. We discuss the generality of our results and possible interactions with other factors.
authors.affiliation: Groupe de Recherche en Ecologie Forestière interuniversitaire, Département des Sciences Biologiques, Université du Québec à Montréal, CP8888, Succ. Centre-Ville, Montréal (QC), Canada. houle@fas.harvard.edu
authors.forename: Alain
authors.initials: A
authors.lastname: Houle
authors.forename: William L
authors.initials: WL
authors.lastname: Vickery
authors.forename: Colin A
authors.initials: CA
authors.lastname: Chapman
mesh_terms: D000818:Animals; D002521:Cercopithecus / Q000502:physiology*; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology*; D005638:Fruit; D011157:Population Dynamics; D012621:Seasons