Forest Investment Account (FIA) - Forest Science Program
FIA Project Y102050

    Determining the Causes and Magnitude of Caribou Mortality During a Moose Population Decline
 
Project lead: Douglas Heard (Ministry of Environment)
Contributing Authors: Heard, Douglas C.; Gillingham, Michael P.; Steenweg, Robin
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Description:
Caribou in the Parsnip watershed live within the Southern Mountain National Ecological Area. Caribou in that area are designated as Threatened by the Canadian Species at Risk Act and are a species at risk under BC Forest and Range Practices Act. We know from 6 years of research, that these are mountain ecotype animals. In winter they remain just below treeline and feed exclusively on arboreal lichen. The Recovery Implementation Plan for Threatened Woodland Caribou accepts the long-held hypothesis that mountain caribou have declined because of increased predation in summer, by wolves. Wolf predation appears to be the major cause of the decline in caribou numbers because 1) logging has increased the abundance of early seral forests, 2) moose numbers have increased in response to the increase in early seral vegetation, and 3) wolf numbers have increased in response to increased moose numbers. Most wolf predation occurs during late spring and summer when snow conditions do not restrict predator movements and wolves can access caribou and their vulnerable calves.
The ultimate management strategy recommended in the Recovery Plan to establish a self-sustaining caribou population, is to limit the amount of early seral vegetation communities that support moose, to levels that would occur under natural disturbance condition. Because of the currently high levels of early seral vegetation resulting from past forest harvesting, even if all forest harvesting was to immediately cease, unlikely given the demand for mountain pine beetle salvage harvesting, it would take several decades before the amount of shrub and herbaceous vegetation declined to natural levels. In the meantime, the environmnet would support high levels of early seral ungulates and their predators. Consequently, the Recovery Plan recommends an interim strategy of reducing moose numbers until the forest age structure returns to a more natural distribution.
Even though the prey reduction strategy was suggested many years ago and is recommended in the Recovery Plan, this approach has never been tested. To promote caribou recovery and to test this hypothesis, The Ministry of Environment has liberalized moose hunting regulations in the Parsnip drainage so that hunters will reduce moose numbers. If hunters reduce moose numbers, then wolf numbers should also decline, predation on caribou should decline and caribou numbers should increase. In the short term however, as moose numbers decline, and wolves are less able to subsist on moose, wolf predation on caribou may increase. This project will quantify predation rates on caribou by monitoring the survival and causes of death of radio-collared caribou as the moose population declines. Radio-collared caribou will be monitored by aircraft and when the radio signal indicates that a caribou has died, the site will be investigated to determine the cause of death.
The results from this project will increase our understanding of why caribou are dying, what fraction of deaths are due to nutritional factors and predation, what predator species are involved, what time of year caribou are most likely to die and when they are at greater predation risk. That information will improve our ability to manage forest resources and develop forest management policy. The results will be relevant to access management planning, if the data suggest that caribou are vulnerable to wolf predation whenever snow conditions, like plowed roads, permit wolves access to the higher elevations occupied by caribou. The results will also suggest how much we should be concerned about proximity of early seral stands to caribou range and the silvicultural treatment within regenerating cutblocks. If grizzly bear predation is a major cause of caribou mortality then cutblocks should be managed so that they are unattractive to grizzly bears or far from caribou range.
Related projects:  FSP_Y091050
Contact: Doug Heard, (250) 614-9903, Doug.Heard@gov.bc.ca

    Deliverables:

Executive summary (32Kb)

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Updated August 16, 2010 

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