November 09, 2017
The whitetail has a dramatic effect on its habitat and on many other species sharing it. But in the tiny area shared by whitetails and woodland caribou, the relationship is unique.
This caribou subspecies is one of the rarest large animals on earth. Its population is thought to hover around 30,000, but only 30 percent of the 57 known herds are self-sustaining. One of the most threatened is the South Selkirk herd inhabiting the mountainous junction of British Columbia, Washington and Idaho. Only about a dozen individuals remain.
As their low number suggests, these caribou face major issues. Poaching, vehicle collisions and habitat loss all are problems, but the greatest threat is predation from wolves and mountain lions. These predators are responsible for high mortality rates among both calves and adults.
To avoid predators, the South Selkirk herd inhabits terrain most other large mammals wouldn't bother with, including high-elevation boreal forests. But even that isn't enough to keep them away from predators — and it's largely because of whitetails.
Over the last century, timber harvest and wildfires have drastically changed the habitat mosaic at elevations lower than identified caribou habitat. The new growth that followed proved to be ideal for whitetails and moose. It also ushered in more predators.
Although lions and wolves don't view caribou as their primary prey, the spatial separation of whitetails and caribou isn't enough. Deer are in effect bringing wolves into range of the caribou. And these caribou can't afford that. Unlike a whitetail doe, a woodland caribou cow isn't mature until the age of 2, rarely produces twins and often only calves every other season.
Wildlife agencies are scrambling for a solution. It includes reducing predator and whitetail populations and, over a longer horizon, restoring lower-elevation habitat to its historical form. It's a challenging task, and it's sad to know the whitetail is making it harder to keep caribou going in the Lower 48.