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This study shows, for the first time, that the evolution of a simple behavior, scrounging, at the individual level can have effects on populations, food chains, and community structure. In particular, the addition of scrounging in consumer populations can allow multiple consumers to coexist while exploiting a single prey. Also, scrounging in the top predator of a tritrophic food chain can stabilize interactions between the top predator, its prey, and its prey's prey. This occurs because the payoffs to scrounging for food in a population are negative frequency dependent, allowing scroungers to invade a population and to coexist with producers at a frequency which is density‐dependent. The presence of scroungers, who do not search for resources but simply use those found by others (producers) reduces the total amount of resource acquired by the group. As scrounging increases with group size, this leads to less resource acquired per individual as the group grows. Ultimately, this limits the size of the group, its impact on its prey, and its ability to outcompete other species. These effects can promote stability and thus increase species diversity. I will further suggest that prey may alter their spatial distribution such that scrounging will be profitable among their predators thus reducing predation rate on the prey. [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]