Area‐restricted search under realistic constraints

Abstract Area‐restricted search (ARS) is one of the most influential and widely used concepts in foraging theory, capturing a simple rule by which animals intensify local search following a resource encounter. Because ARS performs well in many spatially structured environments, it serves as a basic model for interpreting movement patterns across taxa. Despite this prominence, there is no synthesis of when and why ARS is expected to fail, even when implemented correctly. Here, we develop a failure‐based framework that treats departures from ARS not as errors, but as informative consequences of mismatches between a local search rule and ecological reality. We identify multiple classes of failure, spanning informational, spatiotemporal, spatial, cognitive and normative dimensions. These include situations in which encounters are statistically uninformative, self‐generated movement creates misleading cues, environmental change outpaces the temporal horizon of the rule, movement is constrained or costly, or maximizing encounter rates conflicts with other fitness objectives. Many of these failures do not require abandoning ARS. Instead, they point to plausible refinements, such as decaying responses, state dependence, or limits on search duration, all of which preserve the simplicity of ARS while reducing its vulnerability to systematic mismatch.