Intrinsic variation in the availability of food to animal populations reflects the influence of foraging by the animals themselves. Intrinsic variation in food availability provides a link between population density, subsequent food availability and variation in the rate of population increase (r), operating through density-dependent food shortage. In contrast, extrinsic variation in food availability is caused by environmental influences on food or animal abundance, which are independent of animal foraging. Extrinsic variation in food availability is random relative to that arising through intrinsic shortage. Intrinsic and extrinsic variation in food availability can influence animal populations simultaneously. Intrinsic variation will impart a tendency towards an equilibrium between animal and food abundance, which will be progressively obscured by density-independent variation as the influence of extrinsic factors increases.
This study used a large-scale field experiment, in which the density of food-limited feral pig (Sus scrofa L.) populations was manipulated on six sites, to assess the relative influence of intrinsic and extrinsic variation in food availability. The experiment evaluated the influence of pig population density on r and the abundance of food resources measured as pasture biomass.
|Secondary title||Journal of Animal Ecology|
|Region||Australia - national|