by Erling Friis-Baastad
For their own safety, and for the well-being of Yukon wildlife, motorists must slow down. Some years, 10 to 15 Southern Lakes woodland caribou are killed in collisions with vehicles, says Matt Clarke, Southern Lakes regional biologist with Environment Yukon.
The effects of a collision between an animal and a vehicle are often obvious. The carcass remains on the highway, sometimes accompanied by bits of broken auto plastic. An animal may even explode when hit by a large truck.
The numbers have dropped recently, to an average of five to six per year, Clarke says. This year there have already been three so far. Of course, these are the caribou that have been found and reported. Others may well have crawled off into the forest before they died.
What effect do the deaths of the caribou from automotive traffic have on caribou herds? Why are some herds more affected by highway collisions than others? And what about the long-term health of the caribou in the face of expanding human settlements and an increase in traffic throughout their range?
It’s the Carcross caribou herd that interacts the most with humans, says Clarke. “They’re the ones we see on the roadways: Tagish Road, the Alaska Highway and Carcross Road. The largest number of human activities overlap with that herd.”
The Carcross herd is one of three herds that make up the Southern Lakes caribou. The Ibex herd and the Atlin herd are the other two.
“The Ibex herd is primarily contained between Whitehorse and Kusawa Lake, with the Alaska Highway being sort of a northern boundary,” says Clarke. Conditions in their isolated alpine range - such as strong winds that clear snow off the forage - are favourable enough that they don’t need to encounter humans especially often.
The Atlin herd extends into the Yukon from B.C., but remains largely a B.C. management concern.
The sex of the dead caribou found on roadways is significant, Clarke says. If it’s a female, it may well be pregnant, which means two animals have suddenly been removed from the herd. The death of a calf is significant because caribou have a low reproductive rate, usually giving birth to only one calf a year. Twins are very rare.
Meanwhile, even without the death of a pregnant female, calf mortality is high. “The first six months of a caribou’s life are the most tenuous,” Clarke notes. Caribou mothers expend much time and energy caring for their single offspring, but still lose about two-thirds of them. “In the spring, if you were to do a count, you’d probably see about 75 calves per hundred cows,” he says. “In the fall that number is down to about 20 to 25 calves per 100 cows. We consider this a healthy number. Above that is great, below that is where we start to get a little worried.”
Southern Lakes caribou are more numerous than they were back in the very early 1990s, thanks to the initiative of the Carcross/Tagish First Nation, along with the co-operation of five other far-sighted First Nations, as well as the governments of Yukon, B.C., and Canada. Under the Southern Lakes Caribou Recovery Program, the First Nations decided to stop hunting the caribou, and the Yukon government banned the licensed hunt for the Carcross and Ibex herds. The caribou were also the subject of a public education campaign.
This year is the 20th anniversary of those recovery initiatives. The Carcross herd has doubled in size since 1997 and more than doubled since recovery efforts were initiated, says Clarke. However, numbers now appear to have plateaued at about 800. Could highway collisions be a factor?
Harvesting by hunters is usually kept to three per cent of the herd, so those collisions - unintentional harvesting - cut into acceptable harvest numbers. Meanwhile, researchers are trying to determine why some groups of caribou are struck more often than others while crossing a highway.
For instance, near Watson Lake, where there is a higher collision rate (22 reported so far this year), the animals tend to hang around on the highway more, licking salt that had been mixed with the sand spread on icy roads. Further north, toward Whitehorse, caribou appear inclined to cross the highway more directly or hang out in the ditches on the side of the road.
The challenges for caribou management on the highways are great, says Clarke. Local motorists may become complacent after frequent trips along a roadway without incident. Tourists and other drivers just passing through might not expect megafauna on a much-travelled highway. The trucking industry presents special problems because it involves many different companies across the continent, for whom time is, obviously, money.
Both the Highways and Public Works and Environment departments are interested in understanding the issues and communicating with motorists about the threat to wildlife, and the threat to drivers and their passengers. The public can also aid research efforts by reporting road-killed caribou (and moose, bears and other large animals) on the wildlife tip line: 1-800-661-0525.
Clarke suggests that we keep in mind that caribou byways were in place long before highways and motorists came along. Our own travel routes are constructed across ancient “artifacts” of caribou life.
For more information on efforts to conserve Southern Lakes woodland caribou, go to www.yfwcm.ca/mgmtplans/slcrp/caribou.php
This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at www.yukoncollege.yk.ca/research