MOOSE POPULATION HISTORY ON THE NORTHERN YELLOWSTONE WINTER RANGE

Abstract

Moose probably colonized the Northern Yellowstone Winter Range (NYWR) in the latter half of the 19th century. Euro-American settlement of the NYWR occurred at roughly the same time. Legislative protection of moose from hunting in the first half of the 20th century and suppression of wildfires facilitated moose population growth and range expansion. A hunting season in Montana along the northern boundary of Yellowstone National Park, authorized in 1945 in response to perceived damage by moose to willow stands, evidently reduced the moose population quickly and maintained it at moderate densities through 1988. In 1988, landscape-altering wildfires swept through the Yellowstone ecosystem and impacted old growth forest important for moose survival during winter. The moose population associated with the NYWR declined by 75% or more and has shown no sign of recovery by 2002. Several techniques for assessing population trend for moose on the NYWR were tested. Given the problems associated with monitoring a species at low densities with a dispersed social organization and occupying habitats where visibility is limited, aerial population censuses were not useful. A horseback trail survey, a road survey, and counts of moose in early winter or late spring in larger willow stands had greater potential as indices to moose population changes.