Ideal free distribution

[1][2] The theory states that the number of individual animals that will aggregate in various patches is proportional to the amount of resources available in each.

Once the assumptions are met, IFD theory predicts that a population of individuals will distribute themselves equally among patches with the same intrinsic value.

Various deviations may occur initially, but eventually the patches will accommodate the number of individuals that is proportional to the amount of resources they each contain.

[3] Anelosimus eximius, a species of social spiders, live together cooperatively and build large web communities.

[6] In Selous wild dogs, observed pack size did not agree with results of daily per capita food intake.

However, when factoring in distance traveled to hunt into the currency, observed pack size was close to optimal.

This experiment demonstrates that the incorporation of competitive weights into habitat selection can improve predictions of animal distributions.

[9] In another example, competition between sugarbeet root aphid stem mothers for galling sites on the leaves of Populus angustifolia has also been shown to generally follow the Ideal Free Distribution.

After hatching in the spring, female aphids compete with each other for galling sites closest to the stems of the largest leaves.

In 2001, Kraft et al. performed an experiment that tested the IFD's predictions of group choice using humans.

[12] This experiment involved groups of participants choosing between blue and red cards in order to earn points towards prizes.

When the groups’ choice of cards was graphed in relation to the ratios between the points, the slopes demonstrated some undermatching, which is a deviation from the Matching Law.

It is important to keep in mind that IFD does rely on the assumptions previously stated and that all of these qualities are probably not met in the wild.

Cichlid fish[15] also displayed the same subtle difference in predicted vs. actual dispersal numbers in relation to resources.

When psychologists perform tests of this law, they use more sensitive measures to account for deviation from strict matching relationships.

Knowledge of the competitive interactions, effects of travel between sites, number of animals in population, perceptual abilities of these animals, and the relative and absolute resource availability on each patch is required to accurately predict the distribution of a foraging population.