Depensation is when there is a decrease in breeding individuals which leads to reduced production of offspring within a population. This is generally caused by higher levels of predation, the introduction of an invasive species, or the allee effect.1 Parasitism is another contributor to depensation and a population can completely disappear when affected by depensation. 2

Critical depensation is when levels of depensation are high enough that a population cannot sustain itself and recover. If the population drops below the critical depensation level, a population can collapse and a local extinction is possible. 1

Depensatory effects can be grouped into four distinct mechanisms: reduced fertilization, damaged group dynamics, high concentration of predators, and the surrounding environment. 3 These mechanisms should all be considered when identifying depensatory effects in a population using population dynamics models.

  1. Depensation. Retrieved from
  2. Allaby, Michael (2004). Depensation. A dictionary of Ecology. Retrieved from
  3. Liermann, Martin and Hilborn, Ray (2001). Depensation: evidence, models and implications. Fish and Fisheries: 2: 33-58. Retrieved from

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