| Abstract | Encounters between organisms are universal prerequisites for many fundamental ecological processes: Feeding depends on the ability to encounter food items or prey, survival can depend on avoiding encounters with predators, and reproduction depends on mate encounters. The most widely applied null-models of encounter rates are variations of ideal-free gas models. These models, developed in the 19th century by Clausius and Maxwell, assume linearly moving particles with a heterogeneous distribution of velocities. Models of diffusion and dispersal in ecology, on the other hand, often assume homogeneous populations of randomly moving individuals. Actual movements of organisms are best approximated by some mixture of deterministic and autocorrelated random movements, while movement processes within populations or individuals are often heterogeneous. We present mathematical predictions and simulation results of the effect of random movement models and population-level heterogeneity on encounter rates in one and two dimensions. We discuss potential ecological consequences of the results on survival and foraging success, explaining, for example, some properties of observed rates of survival in migrating juvenile salmon. |
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