Distribution of Yellowstone grizzly bears during the 1980s

Grizzly bear (Ursus arctos horribilis) females with young occupied a greater proportion of area east of Yellowstone National Park during 1980-1989 compared to 1973-1979. Occupancy by all bears and females with young was lower in all peripheral areas compared to the Park, but greater east and south compared to north and south of the Park. Observed changes reflect not only a static or slightly increasing population trend, but may also reflect biases in data collection. These biases are discussed and distributions of all observations and females with young are presented. Methodological problems implicit in analyzing changes in distribution of grizzly bears are also discussed.