The
Allee effect is a phenomenon in
biology named after W. C. Allee, who first wrote extensively on it. It describes a positive relation between population density and the
per capita growth rate. In other words, for smaller populations, the reproduction and survival of individuals decreases. This effect usually saturates or disappears as populations get larger.
The effect may be due to any number of causes. In some species, reproduction—finding a mate in particular—may be increasingly difficult as the population density decreases. Other species may use strategies (such as
schooling in
fish) that are more effective for larger populations.
References
Further reading
- Animal Aggregations. A study in General Sociology., W. C. Allee, University of Chicago Press