Ideal Free Distribution
IFD
In ecology, a way in which animals distribute themselves among several patches of resources. The theory predicts that the distribution of animals among patches will minimize resource competition and maximize fitness.
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Origin
Introduced by ecologists Stephen Fretwell and Henry Lucas Jr. in their 1970 paper "On Territorial Behavior and Other Factors Influencing Habitat Distribution in Birds". The model predicts that freely moving individuals distribute themselves across resource patches so that local fitness is equalized in all occupied habitats. Their work became foundational in behavioral ecology, with applications extending to human behavior, territorial colonization, and resource distribution across species.
Updated February 22, 2026