No evidence that predator control will save endangered mountain caribou, study says

Killing wolves hasn’t slowed caribou decline; scientists suggest renewed emphasis on securing habitat.

A wolf trots across the beach in the early morning light.
Photo by Ian Harland.

Detecting errors that overturn conclusions from previous research, a new study shows that addressing potential threats from wolves has not in fact slowed the decline of mountain caribou in British Columbia and Alberta. The freely-available open-access paper was published in the international peer-reviewed journal, Biodiversity and Conservation, by scientists from Raincoast Conservation Foundation and the Universities of Alberta, British Columbia, and Victoria.

The scientists looked closely at the data provided in an enormously influential 2019 study that examined how 18 caribou populations responded to different ‘treatments’ (wolf culling, maternal penning, moose reduction, and/or combinations thereof) and ‘controls’.  

Using a standard but previously neglected statistical step, the new research arrived at strikingly different conclusions. The team found that the government-sponsored killing of wolves and other treatments had no detectable effect. 

The implications of the previous scientific errors are profound. For example, announced shortly after the previous study (and citing its conclusions), the BC government invested in an expanded wolf program. Over the winter of 2019-20, 463 wolves were killed. “If managers are interested in using the best available evidence to inform policy, these findings should trigger an immediate re-evaluation of expensive, socially contentious – and ultimately ineffective – policy,” said Chris Darimont, co-author on the study, Professor at the University of Victoria, and Science Director for Raincoast Conservation Foundation. 

Digging deeper into the data, the authors additionally found an important new signal. Not linked to any management action, population changes in caribou were instead associated with the four different ecotypes (or forms) of caribou. Of these, the southernmost “Deep-Snow mountain caribou,” found from Wells Gray Park into the Kootenays, experienced among the steepest declines. 

“Intact forests provide caribou with important lichens as food, as well as refuge from wolves and separation from other prey animals, including elk, moose, and deer,” said Lee Harding, retired Canadian Wildlife Service biologist and lead author on the study. “Without them, caribou must constantly be on the move to find food, exposing them on all sides. Predators are just one of the hazards.”

“Worse than tax-funded programs to kill wolves in error,” Darimont says, “is the free pass that such an ill-advised diversion granted to industry, which continued to aggressively destroy habitat.” Large scale forestry as well as oil and gas activities removes old growth forest that provides critical habitat and food for endangered caribou, particularly those in the southern part of remaining ranges. 

“Unless governments move quickly to protect the remaining and  irreplaceable habitat, it will continue to vanish at astonishing rates, setting up increasingly desperate conditions from which caribou will never recover,” says Darimont.