In the winter of 2019/2020, some 463 wolves were killed in British Columbia as part of a state-sponsored culling program to help revive the dwindling mountain caribou population. According to a new study, these deaths were pointless and based on dodgy statistics.
The mountain caribou, an ecotype of the woodland caribou subspecies (Rangifer tarandus caribou) that was once found as far south as Idaho and Montana, became listed as an “endangered” species by Canadian wildlife authorities in 2012 after recent decades had seen a rapid decline of population numbers. Many argued this was primarily due to years of continued habitat degradation, while others proposed that predators and freakishly high levels of predation were the leading culprits.
In 2005, this latter theory sparked the British Columbia government to roll out a costly “caribou recovery plan” that sent sharpshooters in low-flying helicopters to kill wolves. With less hungry predators around, they argued the mountain caribou population would bounce back.
By early 2019, a study supported the wolf cull, claiming that the caribou could be saved through a wildlife management operation involving the killing of wolves and fencing pregnant caribou. Affirmed by the study, the provincial government went on to kill 463 wolves over the winter of 2019/2020, according to an email sent to The Narwhal from the Ministry of Forests, Lands, Natural Resources Operations and Rural Development.
Now, reported in the journal Biodiversity and Conservation, scientists argue the 2019 research was wrong. The culling, effectively, was based on false assumptions. Researchers led by the University of Alberta used data simulations on mountain caribou across BC and found that wolves had little to do with their demise of the mountain caribou. For example, some of the steepest declines were seen among deep-snow caribou living in southern British Columbia where wolves are not the main predators of caribou: cougars, bears, and wolverines are.
The study argues that the 2019 study made the fatal error of not using a null model. This is a statistical tool often used in ecological data that determines whether a factor has a real impact on the overall pattern or whether the trend is just part of a random variation. Once the researchers ran a null model for the data, the impact of wolf culling and caribou pens was not nearly as important as the 2019 study indicated.
If their findings are correct, it means the wolves culled over the past season died in vain, having little effect on the overall health of the mountain caribou population.
"No matter how you calculate it, the statistics don't back up culling wolves or fencing in caribou," co-author Viktoria Wagner, an assistant professor in the University of Alberta's Department of Biological Sciences, said in a statement.
But the question remains: what is causing the slump of mountain caribou? These researchers argue that habitat destruction and human activity – namely the loss of habitat to logging, snowpack variation, and snowmobiling – are the main contributors to the decline of caribou.
"Forests provide caribou with refuge from wolves and separation from other prey animals, including elk, moose, and deer," added Lee Harding, a 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."