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Why a Reserve Network?
Case Study of the Grizzly Bear


large carnivoreLarge animals at the top of the food web, like grizzly bears, wolverines, and wolves, require large areas. Scientists estimate that at least 2,000 individuals of any one species need to interact in order to avoid inbreeding, and to be able to absorb and recover from food shortages, disease, and widespread disturbances like fire.


More than 120,000 km2 of land is required to sustain 2,000 grizzly bears. No park or wilderness area in North America is this large. Yellowstone National Park in Wyoming and Montana encompasses 12,000 km2 and Banff National Park in Canada covers roughly half that area.

The solution to this problem is to maintain or restore links between isolated groups of animals, so that collectively they make up the required 2,000 individuals. Wildlife linkages or corridors can provide the means by which individuals move between sub-groups of the larger population - and in so doing, avoid inbreeding and are able to escape or re-colonize areas swept by disease, or other disturbances.


The simplistic view of a wildlife corridor is one of a linear conduit through which an animal moves from point A to point B. However, for many species, grizzly bears included, corridors will need to be areas in which low densities of the animals can live and survive. Therefore, corridor widths may be based on home range diameters for some of the larger users (in the order of 50km for grizzly bears), and human use will need to be managed at levels compatible with the most sensitive species (e.g. road densities near 0.3km/km2 for grizzly bears).


The conventional model of nature reserves - discrete and isolated entities in a human-dominated landscape - does not apply well to animals like the grizzly bear and wolverine. Opportunities for creating single reserves big enough to sustain viable populations of large carnivores are extremely limited.

Yet most of the Rocky Mountain region in north- western North America is still lightly inhabited by humans and is well suited to a model in which reserves are interconnected with functional corridors that span large areas.

Noss, R., H.B. Quigle, M.G. Hornocker, T. Merrill and P.C. Paquet. 1996. Conservation biology and carnivore conservation in the Rocky Mountains. Journal of Conservation Biology, 10(4):949-963.

Metzgar, L.H. and M. Bader. 1992. Large mammal predators in the northern Rockies: grizzly bears and habitat. Northwest Environmental Journal 8:231- 233.


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