COMPLEMENTARY FEEDING NICHES SUSTAINED BY SIZE‐SELECTIVE PREDATION1

Abstract

A study of the planktonic communities of 24 similar ponds in the mountains of Colorado supports the hypothesis that one predator population can sustain another as a result of size‐selective predation on the prey of both predators. A highly selective predator excludes its preferred (large) food items and thus favors the presence of suboptimal (smaller‐sized) prey populations which are the preferred food of the second, dependent, predator. The suboptimal prey species are found only with size‐selective predators, and it is probable that these are the only suitable prey species for the dependent predator. This interaction can occur in simple communities but also appears to be common in more diverse, complex communities. To support the discussion of this interaction, the electivity coefficients and predation pressures of three freshwater planktivores were estimated.