Presented by: Doug Heard

Predation has both direct and indirect effects on prey. I considered the possibility that caribou population growth may be limited by summer food because they quit ‘surfing the green wave’, because of the increased risk of wolf predation at lower elevations. If that were the case, then supplemental feeding in might compensate for that limitation and contribute to population growth. To test that hypothesis, we fed high-quality food pellets to free-ranging caribou in the Kennedy Siding caribou herd in central BC, each fall for 7 years, starting in 2015. Beginning in 2016, the Province of British Columbia began a concurrent annual program to promote caribou population increase by attempting to remove most wolves within the Kennedy Siding and the adjacent caribou herds’ ranges. After 4 years, in the Kennedy Siding herd, when both feeding and wolf reduction occurred concurrently, lambda was 1.16 and in the Quintette herd, where the only management action was wolf reduction, lambda was1.08. The higher growth rate of the Kennedy Siding herd was due to higher cow survival (96.2%/yr vs. 88.9%/yr). During the 5th year of this experiment, the Kennedy Siding herd grew at a similar rate as before (λ=1.14) but the numbers in Quintette herd did not change (λ=1.01). On the surface those results lend further support to our previous conclusion that supplemental feeding increased herd growth. However, part of the increase in Kennedy Siding herd numbers may have been due to bulls coming from elsewhere.