One way in which animals coexist is through temporal separation of feeding activities. This separation directly reduces interference competition, but potentially not exploitive competition. To reduce exploitive competition, coexisting species tend to utilize different microhabitats and/or achieve different feeding efforts across microhabitats. However, 1 factor that has generally not been considered with regards to its impacts on competition, and thus coexistence, is predation risk. As different predators are active during the day and at night, the location of safe areas across the landscape can vary temporally. If so, then temporally separated prey species would likely forage in different areas thus reducing exploitive competition. However, if predation risk across the landscape is similar for nocturnal and diurnal species, then both could restrict their foraging to the same microhabitats, thus increasing exploitive competition. To explore these alternative possibilities, we manipulated grass height in an African grassland to create microhabitats that varied in predation risk. We then estimated perceived predation risk of both nocturnal and diurnal rodents in these microhabitats by recording giving-up densities (GUDs) in artificial resource patches. We found that despite differences in predators, both nocturnal and diurnal rodents preferred feeding in the same microhabitats, and they achieved similar feeding efforts within these microhabitats. This suggests that despite the prevention of interference competition through temporal partitioning, the spatial similarities in perceived predation risk in relation to cover likely increase exploitive competition between these rodents. However, as both nocturnal and diurnal rodents were present in the study area, it is likely that some other mechanism (e.g., varied diets) allows them to coexist.
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Vol. 97 • No. 2