Intraspecific competition

March 28, 2013, 5:33 pm
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A male Blackbird (Turdus merula) singing. Bird song often functions as a signal in territory defense. (By Malene Thyssen,

Intraspecific competition is the conflict over resources between members of the same species. Individuals may compete over mates, water, sunlight, territory or food energy sources. Intraspecific competition is an important factor limiting the population size of many species.

Intraspecific population regulation

caption Competition among individuals of the bunchgrass Hilaria rigida (big galleta grass) results in an even spatial dispersion of individuals. (Photo by R. Robberecht)

If members of the same species are competing for limited resources, then each individual would receive fewer resources when the population size of intraspecific competitors increases. Fewer resources per individual will (1) decrease the growth rates of individuals, (2) increase the chance that individuals die of starvation, or (3) decrease the number of offspring that a female can produce. Thus, as population density increases, there will be a resultant decrease in population growth rate. Intraspecific competition can cause populations to stop growing when they reach their carrying capacity (see logistic growth).

Intraspecific competition and patterns of spatial dispersion

Intraspecific competition can influence the spatial dispersion of organisms in a population. For example, if plants are competing for soil resources, there may be a limit to how close together individual plants of the same species can live. Thus, intraspecific competition can result in plants having an even pattern of distribution across the environment.

Limiting the effects of intraspecific competition

caption Tiger marking territory. (Photo from Save the Tiger Fund)

Individuals may try to limit competition for resources by defending limited resources from use by other members of their species. The physical defense of resources from other members of the same species is an example of interference competition. In some cases animals may defend territories to allow them to have exclusive use of the resources in the territory. Animals may defend territories to provide them with access to food or other resources or to provide them with a space where they can safely raise their young. Males of many species defend territories from other males of their own species for exclusive access rights to mating with the females living in their territory.

Further reading

  • Campbell, N.A., J.B. Reece, and L.G. Mitchhell. 2006. Biology. Addison Wesley Longman, Inc. Menlo Park, CA. ISBN: 080537146X
  • Raven, P.H., G.B. Johnson, J.B. Losos, K.A. Mason, and S.R. Singer. 2008. Biology, 8th edition. McGraw Hill, New York, NY. ISBN: 0073227390


(2013). Intraspecific competition. Retrieved from


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