The B.C. government has long justified its controversial grizzly bear hunt by saying it's based on sound science.
But new research by a team of biologists from three universities has found the kill limits are being exceeded in many areas of B.C. – up to 70 per cent of the time – because of unpredictable factors, such as bears getting killed in collisions with vehicles, or being shot by ranchers who don't report the incidents.
"The bottom line is human-caused mortality from all sources, 85 per cent of which is hunting, is consistently over target. These overkills are frequent and they are geographically widespread," said Chris Darimont, a conservation scientist at the University of Victoria, one of several authors on the study.
He said by allowing too many bears to be killed, the government is "playing Russian roulette" with B.C.'s vulnerable grizzly bears, because the population in some regions could easily get knocked down to a level from which it couldn't recover.
"If I was managing bears I wouldn't manage them this way if I wanted to have them here in the future," said Dr. Darimont, who called for a more precautionary approach.
The B.C. government's support for a trophy grizzly bear hunt has been under attack from environmental groups, and in 2004 the European Union banned the import of grizzly bear trophies from B.C., saying the hunt was not environmentally sound.
But the government has worked with an independent panel of grizzly bear scientists to set harvest limits intended to ensure the sustainability of bear populations. Under the strategy, the province is divided into more than 50 sub-zones, or grizzly bear population units, where the harvest levels vary, depending on the number of bears in the area, the estimated productivity of the population and the known number of bear mortalities.
"It's very complex but we noted they didn't incorporate all the dimensions of uncertainty in setting those limits," Dr. Darimont said.
"You need to know a few things if you want to allocate how many bears will be killed," he said. "You need to know how many bears there are … and for most of the province there are no on-the-ground estimates … you also need to know … how fast do bear populations grow and therefore how much can we skim off the top?"
To further complicate the picture, he said, the government needs to know the level of unreported mortalities, where bears are shot by people who don't report the kills.
"Those are the three pieces of information the ministry needs to calculate the [harvest] limits," Dr. Darimont said. "But any one of those things has tremendous uncertainty around them. How many bears are there? Who knows? How fast can they reproduce? Who knows? What's the true level of unreported mortality? Who knows?"
By studying all the grizzly bear data available over about an eight-year period, the researchers from UVic, Simon Fraser University and the University of British Columbia developed simulations based on a range of population and mortality estimates. Using the provincial estimates, they found overkills in 19 per cent of the population units. But that number climbed when they factored in the range of uncertainty.
"We did the audit again and found that not in 19 per cent of cases, but closer to 70 per cent of cases, there were likely overkills," Dr. Darimont said.
Kyle Artelle, a PhD student at SFU and lead author on the paper, said if the government wants to keep the level of risk of overkilling fairly low, it will have to eliminate hunting in about one-third of the population units.
In addition to their university affiliations, Dr. Darimont and Mr. Artelle both work for the Raincoast Conservation Foundation, a non-profit which 10 years ago took the provincial government to court to get grizzly bear mortality data released. That data was the basis for the study.