Carnivore Re-Colonisation: Reality, Possibility and a Non-Equilibrium Century for Grizzly Bears in the Southern Yellowstone Ecosystem

Expansion was exponential and the area occupied by grizzly bears doubled approximately every 20 years. A complementary analysis of bear occurrence in Grand Teton National Park also suggests an unprecedented period of rapid expansion during the last 20-30 years. The grizzly bear population currently has re-occupied about 50% of the southern GYE.

Based on assumptions of continued protection and ecological stasis, our model suggests total occupancy in 25 years. Alternatively, extrapolation of linear expansion rates from the period prior to protection suggests total occupancy could take > 100 years. Analyses of historical trends can be useful as a restoration tool because they enable a framework and timeline to be constructed to pre-emptively address the social challenges affecting future carnivore recovery.

One of the purposes of the dataset is to predict when grizzly bear occupation of Southern Yellowstone Ecosystem will be total. We focused on a 24,000 square kilometer mosaic of mostly public land that is managed by various federal and state agencies. Our analysis of changes in grizzly bear distribution during 1900-2000 was divided into 20-year periods.

For each, we used various data sources for grizzly bear occurrence to create digital maps of bear distribution using ArcView GIS 32. (ESRI, Redlands, CA) We digitized reports, interviews, conflicts, mortalities and observations as points. We created a polygon for the 1920 source data, a hand-drawn distribution map by Merriam (1922).

More methodology given in Pyare, 2004 paper.