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Providing evidence to improve practice

Individual study: Northern Yellowstone elk after wolf restoration

Published source details

White P.J. & Garrott R.A. (2005) Northern Yellowstone elk after wolf restoration. Wildlife Society Bulletin, 33, 942-955


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Translocate predators for ecosystem restoration Terrestrial Mammal Conservation

A before-and-after study in 1986–2004 in a grassland and forest reserve in Wyoming, USA (White & Garrott 2005) found that after the translocation of wolves Canis lupus to the reserve, adult elk Cervus canadensis numbers and elk calf:cow ratios approximately halved. Results were not subjected to statistical analysis. Nine years after wolves were translocated, there were fewer adult elk (8,335) and a lower calf:cow ratio (12 calves/100 female elk) than the average before wolf translocation (adult elk: 16,664; 25 calves/100 female elk). A similar number of elk that had migrated out of the park were killed by hunters before (1,148 elk/year) and after (1,297 elk/year) wolves were translocated. Wolves were translocated into Yellowstone National Park in 1995. Between 1996 and 2004 wolf numbers increased from 21 to 106. Elk adults and calves were counted from aeroplanes annually during December–January 1986–2004. No counts were conducted during the winters of 1996 and 1997.

(Summarised by Ricardo Rocha)

Translocate mammals to reduce overpopulation Terrestrial Mammal Conservation

A before-and-after study in 1986–2004 in a grassland and forest reserve in Wyoming, USA (White & Garrott 2005) found that adult elk Cervus canadensis numbers and elk calf:cow ratios approximately halved after the translocation of wolves Canis lupus to the reserve. Results were not subject to statistical analysis. Nine years after wolves were translocated, there were fewer adult elk (8,335) and a lower calf:cow ratio (12 calves/100 female elk) than the average before wolf translocation (adult elk: 16,664; 25 calves/100 female elk). A similar number of elk that had migrated out of the park were killed by hunters before (1,148 elk/year) and after (1,297 elk/year) wolves were translocated. Wolves were translocated into Yellowstone National Park in 1995. Between 1996 and 2004 wolf numbers increased from 21 to 106. Elk adults and calves were counted from aeroplanes annually during December–January 1986–2004. No counts were conducted during the winters of 1996 and 1997.

(Summarised by Ricardo Rocha)