# Delayed density dependence

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In [population ecology](/source/population_ecology) '''delayed density dependence''' describes a situation where [population growth](/source/population_growth) is controlled by [negative feedback](/source/negative_feedback) operating with a time lag.<ref>BONSALL, M.B., HASAN, N. and NAKAMURA, K., 2007. Density dependence and noise determine the long-term dynamics of two species of lady beetle (Coleoptera: Coccinellidae: Epilachninae) in the Indonesian tropics. Ecological Entomology, 32(1), pp. 28-37.</ref>

==Population cycles==

Delayed [density dependence](/source/density_dependence) has been used by [ecologists](/source/ecology) to explain [population cycle](/source/population_cycle)s.<ref name="Turchin">TURCHIN, P., TAYLOR, A.D. and REEVE, J.D., 1999. Dynamical role of predators in population cycles of a forest insect: An experimental test. Science, 285(5430), pp. 1068-1071.</ref> Ecologists have been unable to successfully explain regular population cycles for many decades; delayed density dependence may hold the answer.<ref name="Turchin"/> Here populations are allowed to increase above their normal [capacity](/source/Carrying_capacity) because there is a time lag until [negative feedback](/source/negative_feedback) mechanisms bring the population back down. This effect has been used to explain the widely fluctuating population cycles of [lemmings](/source/lemmings),<ref name="framstad">FRAMSTAD, E., STENSETH, N.C., BJORNSTAD, O.N. and FALCK, W., 1997. Limit cycles in Norwegian lemmings: Tensions between phase-dependence and density-dependence. Proceedings of the Royal Society B: Biological Sciences, 264(1378), pp. 31-38.</ref> forest [insects](/source/insects) as well as the population cycles of larger [mammals](/source/mammals) such as [moose](/source/moose) and [wolves](/source/wolves).<ref>POST, E., STENSETH, N.C., PETERSON, R.O., VUCETICH, J.A. and ELLIS, A.M., 2002. Phase dependence and population cycles in a large-mammal predator-prey system. Ecology, 83(11), pp. 2997-3002.</ref> Other causes of population cycles include cycling [abiotic](/source/abiotic) factors.<ref>HUNTER, M.D. and PRICE, P.W., 2000. Detecting cycles and delayed density dependence: A reply to Turchin and Berryman. Ecological Entomology, 25(1), pp. 122-124.</ref>

==Causes==

The causes of delayed density dependence vary in each situation. In lemmings, food supply and [predation](/source/predation) are the most important factors that lead to delayed density dependence.<ref name="framstad"/> 
[Competition](/source/Competition) between life stages is another cause. In some species of [moth](/source/moth) the practice of [egg](/source/Egg_(biology)) [cannibalism](/source/cannibalism) takes place where older moths eat eggs of their own species.<ref name="briggs">BRIGGS, C.J., SAIT, S.M., BEGON, M., THOMPSON, D.J. and GODFRAY, H.C.J., 2000. What causes generation cycles in populations of stored-product moths? Journal of Animal Ecology, 69(2), pp. 352-366.</ref> This produces imbalances in the population levels of different [generations](/source/Generation) leading to delayed density dependence.<ref name="briggs"/> 
[Disease](/source/Disease) is another causative factor. The delay is introduced because of the time it takes for enough [susceptible individual](/source/susceptible_individual)s to be present for the disease to spread again.<ref>[BJØRNSTAD, O.N.](/source/Ottar_Nordal_Bj%C3%B8rnstad), SAIT, S.M., STENSETH, N.C., THOMPSON, D.J. and BEGON, M., 2001. The impact of specialized enemies on the dimensionality of host dynamics. Nature, 409(6823), pp. 1001-1006.</ref>
The delay to [sexual maturity](/source/sexual_maturity) introduces delayed density dependence in many instances. In this case there is density dependent inhibition applied to organisms when they are sexually immature.<ref>COOKE, K.L., ELDERKIN, R.H. and HUANG, W., 2006. Predator-prey interactions with delays due to juvenile maturation. SIAM Journal on Applied Mathematics, 66(3), pp. 1050-1079.</ref> When this generation reaches sexual maturity there are fewer [offspring](/source/offspring), continuing the pattern.

==Methods of detection==

[Autocorrelation](/source/Autocorrelation) is the principal method by which delayed density dependence can be detected. [Time series](/source/Time_series) are analysed for repeating patterns.<ref>(1998). Insect populations in theory and in practice: 19th Symposium of the Royal Entomological Society 10–11 September 1997 at the University of Newcastle. Dordrecht, Kluwer Academic.</ref>

==See also==

*[Density-dependent inhibition](/source/Density-dependent_inhibition)
*[Population cycle](/source/Population_cycle)
*[Population dynamics](/source/Population_dynamics)
==References==
{{reflist}}
Category:Population ecology

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Adapted from the Wikipedia article [Delayed density dependence](https://en.wikipedia.org/wiki/Delayed_density_dependence) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Delayed_density_dependence?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.