Since the spatial extent and degree of exclusivity of an animal's home range influence its access to important resources, such as food, shelter, and mates, patterns of animal space use can also exert a powerful influence on the demography of animal populations. This is particularly the case in species where individuals actively defend home ranges against other individuals for all or part of the year, as occurs in territorial birds such as great tits and red grouse; in many vole and other rodent species; and in carnivores such as coyotes and wolves. In such populations, the active defense of home ranges results in significant numbers of individuals being forced into either dispersing and setting up home ranges in marginal habitats, or existing as nonresident, 'floaters' within the population. Usually juveniles or lower-ranking adults, these individuals tend to have diminished rates of survival, and have either reduced fecundity or do not breed at all.
It has been argued that in species with cyclical population dynamics, such as red grouse and a number of vole and other rodent species, the effects of home range defense act as a destabilizing factor, due to delayed density dependence between the response ofindividual home range sizes and levels of defense to changes in population abundance. More commonly, however, the existence of a reservoir of 'surplus' nonresident individuals arising from home range defense is considered to act as a stabilizing factor on population size, reducing the propensity for fluctuations and increasing a population's resilience to perturbation. This has implications for efforts for management of populations in which this arises: for example, research has shown that nonresident coyotes rapidly replace breeding individuals killed in control efforts, severely hampering efforts to reduce coyote population sizes through culling.
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