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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. [ABSTRACT FROM AUTHOR]

Primate ecological studies can benefit from accessing the canopy to estimate intra-tree and inter-tree variation in food availability and nutrient value, patch and subpatch depletion, foraging efficiency, as well as nest structure and nesting behaviors, parasitic transmission and predator detectability. We compare several ways to access the canopy and examine their suitability for studies of primates. Two of them—the Single Rope Technique and the Climbing Spur Method—allow people to safely access almost all kinds of trees, regardless of their size, height or shape. Modern climbing gear and contemporaneous safety protocols, derived from rock climbers, speleologists, and industrial arborists, are reliable and appropriate for primate ecological studies. Climbing gear is specialized and still expensive for students, but tree climbing can be dangerous during specific maneuvres. Consequently, formal training and preliminary experience are essential before attempting to collect data. We discuss the physics of falling, risk assessment associated with a fall, knots, gear and safety precautions. Finally, we propose a Tree Climbing Safety Protocol adapted for 2 climbing methods and primate field ecology. Researchers should be aware that climbing safety depends on their own judgment, which must be based on competent instruction, experience, and a realistic assessment of climbing ability. Therefore, the information we provide should be used only to supplement competent personal instruction and training in situ. Although most primate observations have been and will mostly be done from the ground in the future, canopy information complements the observations. Canopy data will add a significant new dimension to our knowledge of primates by providing strategic information otherwise unavailable. [ABSTRACT FROM AUTHOR]

This study tests five mechanisms for the coexistence of red squirrels (Tamiasciurus hudsonicus) and eastern chipmunks (Tamias striatus). These mechanisms, based on optimal foraging theory, depend on differences between the two species in habitat over space and time. The mechanisms are related to: 1) habitat; 2) microhabitat; 3) foraging and travel costs; 4); seasonal variation in predation risk; and 5) seasonal variation in thermoregulatory costs. Each speciesi foraging efficiency was estimated, using GUDs (Giving-up-densities) from February to July 1995 at the Morgan Arboretum, Ste. Anne-de-Bellevue, Quebec, Canada. GUDs were measured in 36 aluminum seed trays, each containing 20g of sunflower seeds, mixed with 2.25 l of kiln dried sand. Trays were set in three habitats (coniferous, deciduous and mixed forest), separated by at least 300 m with 6 pairs of trays per habitat. In general, the chipmunk was more efficient (left lower GUDs) than the red squirrel. The red squirrel was more efficient than the chipmunk in the coniferous forest during the spring and had exclusive access to food during the winter when the chipmunk was in hibernation. The chipmunk was the more efficient forager in the mixed forest in both spring andsummer. This spatio-temporal trade-off in foraging efficiency constitutes a mechanism which can promote coexistence between these two diurnal rodents. [ABSTRACT FROM AUTHOR]