Ideal free distribution

Ideal Free Distribution (IFD) is a theory in ecology and behavioral ecology that explains how animals distribute themselves among several patches of resources. The theory posits that individuals will select habitats and resources in a way that maximizes their fitness, or reproductive success, based on the quality and quantity of resources available and the number of competitors present. The "ideal" in IFD assumes that animals have complete knowledge of resource availability and competitor density in all patches, while "free" indicates that individuals are free to move to any patch they choose without restriction.

Overview

The concept of Ideal Free Distribution was first introduced by Fretwell and Lucas in 1969. It is grounded in the principle that animals are rational and will distribute themselves in a manner that equalizes the rate of resource acquisition across all patches. This means that as a patch becomes more crowded, the benefit of moving to a less crowded patch increases, even if the absolute quality of the resource is lower. The distribution continues to adjust until no individual can increase its fitness by moving to a different patch, reaching an equilibrium where the fitness payoff is equal across patches.

Assumptions

The IFD model is based on several key assumptions:

• Individuals have perfect knowledge of the quality and quantity of resources and the number of competitors in all patches.
• There is free movement of individuals between patches.
• Individuals aim to maximize their fitness.
• The habitat is homogeneous, except for the distribution of resources.

Applications

IFD has been applied in various fields within ecology and beyond, including the study of animal foraging behavior, habitat selection, and human resource use. It has been used to predict the distribution of animals in natural environments, such as how fish distribute themselves among different feeding areas or how birds choose nesting sites. In conservation biology, understanding IFD can help in the design of reserves and protected areas by predicting how animals will respond to changes in habitat and resource distribution.

Limitations

While IFD provides a useful framework for understanding animal distribution, it has limitations. The assumption of perfect knowledge is rarely met in natural settings, and animals may use heuristics or past experiences rather than immediate, perfect information to make decisions. Additionally, the model does not account for social factors that may influence distribution, such as territoriality or social hierarchies.

See Also

• Behavioral ecology
• Habitat selection
• Resource distribution
• Conservation biology