Impacts across levels: Resource biodiversity is affected by predation and competition pressure on the forager level

Abstract Foraging animals create nonrandom patterns of diversity and abundance within resource communities. Perceiving predation pressure and intraspecific competition for food resources, foragers can alter space use patterns, foraging intensity, and preference for specific functional traits of their resources. Consequently, variation in the behavior of foragers may alter the patterns of diversity in resource communities. We investigated the concurrent effects of predation risk to foragers, and of forager density on the diversity of resources in an experimental resource community. We created resource landscapes using experimental foraging patches in near‐natural rodent enclosures and replicated the experiment with two rodent species, which differed in their sociality and foraging ecology, so the importance of intraspecific competition could vary. For both species, predation risk (induced via open vs. covered foraging patches) led to reduced foraging activity (higher giving up densities). Consequently, resource diversity was higher in foraging patches and landscapes with greater perceived predation risk than in safe foraging patches and landscapes. Increased forager density in safe conditions decreased resource community diversity only in the less social species, which forages on depletable, ephemeral resources. Forager density had no effect under perceived predation risk. The more sociable species, which feeds on grasses that are not easily depletable, did not alter its foraging behavior with density. Our findings illustrate the overall importance of predation risk, not only on behavior but also on lower trophic levels, and that density effects are mediated by both predation risk and species ecology. Thus, predation, competition, and sociality at the consumer level can indirectly affect local and regional dynamics of communities of resource species.