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Providing evidence to improve practice

Individual study: Manipulations of black bear and coyote affect caribou calf survival

Published source details

Lewis K.P., Gullage S.E., Fifield D.A., Jennings D.H. & Mahoney S.P. (2017) Manipulations of black bear and coyote affect caribou calf survival. The Journal of Wildlife Management, 81, 122-132


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

Provide diversionary feeding for predators Terrestrial Mammal Conservation

A controlled, before-and-after study in 2008–2011 in four boreal forest, peatland and heath sites in Newfoundland, Canada (Lewis et al. 2017) found that diversionary feeding of predators appeared to increase woodland caribou Rangifer tarandus calf survival. However, the significance of the intervention was not explicitly tested. Caribou calf survival during diversionary feeding (70-day survival: 23%; 182-day survival: 14%) appeared to be higher than before diversionary feeding commenced (70-day survival: 9%; 182-day survival: 7%) though there was high variability in these data. Survival rates across these two periods at sites without diversionary feeding were stable (70-day survival: 56–59%; 182-day survival: 41–47%). Supplementary food was mostly taken by American black bears Ursus americanus which, along with coyotes Canis latrans, were the most frequent confirmed predators of caribou calves. At one site, 500-kg bags of bakery waste were distributed in a grid of 4.5 × 4.3-km quadrats, covering most of the caribou calving area. Food was provided from before 25 May until mid-July in 2010 and 2011 and was replenished weekly as required. In 2011, food was supplemented with beaver Castor canadensis carcasses. Three other caribou calving sites received no supplementary food. Across all sites, 313 caribou calves were radio-collared in late May to early June of 2008–2011, when 1–5 days old, and were monitored by radio-tracking through to November.

(Summarised by Nick Littlewood)

Remove or control predators Terrestrial Mammal Conservation

A controlled, before-and-after study in 2008–2013 in four boreal forest, peatland and heath sites in Newfoundland, Canada (Lewis et al. 2017) found that controlling coyotes Canis latrans increased caribou Rangifer tarandus calf survival. Caribou calf survival was higher when coyotes were controlled (70-day survival: 41%; 182-day survival: 32%) compared to before coyote control was carried out (70-day survival: 9%; 182-day survival: 7%). Survival rates across these two periods at sites without coyote control were stable (70-day survival: 52–58%; 182-day survival: 47%). At one site (covering 480 km2), lethal neck snares were set in March or April of 2012 and 2013 and were removed one week before caribou calving commenced in May. Forty coyotes were removed over these two years. Coyotes were not controlled at three other caribou calving sites. Caribou calves were radio-collared in late May to early June of 2008–2009 (193 calves) and 2012–2013 (103 calves), when 1–5-days old, and were monitored by radio-tracking through to November.

(Summarised by Nick Littlewood)