We’ve heard a lot about caribou recently, mostly in the fight over drilling in the Arctic National Wildlife Refuge. But fewer people know that the Northwest is home to the last remaining caribou herd to inhabit the lower 48 states. They are considered the most endangered large mammal in the continental United States.
Woodland caribou once ranged in New England, the Upper Midwest, and as far south as the Salmon River in Idaho. Today, the last survivors, the tiny Selkirk herd, occupy only a small range in northeast Washington, northern Idaho, and an adjacent portion of British Columbia. Even in BC, where caribou are relatively abundant, their range has shrunk dramatically as logging, development, and other habitat disruption makes itself felt in the Canadian Rockies. (Click on the small map at left for a look at present and historical range.)
The Selkirk herd has mimicked larger trends in North American caribou. Once numbering between 200 and 400, the herd has clung to a precarious existence since its listing as an endangered species in 1993. At present, the herd comprises only 35 animals, down from a recent high of 52 in 1995, which was achieved partly by three years of "augmentation" during the late-1980s when caribou from northern BC were transplanted to sustain the dwindling population.
The causes for the decline of caribou are many. In order to thrive, woodland caribou require relatively intact mountain forests. (Their preferred food is a lichen found only on subalpine trees at least 50 years old.) So, in that sense, their fading populations are a good proxy for the extent to which we have disturbed these ecosystems. (For a look at the Selkirk population trend, click on the chart at left.)
In the Selkirk Mountains, for instance, clearcut logging, together with the road network to support it, reduced high-quality habitat and forage for the caribou. But logging had another, more pernicious, effect: the re-growth was abundant forage for deer, whose population boomed, followed quickly by a booming population of cougars. Cougars, who had formerly been rare in the Selkirks, would often bump into caribou and decide they didn’t mind a little variety in their diets. So, "natural" predation turned out to be a big pressure on the few remaining caribou.
Over the last five to six years, the population has been fairly stable, hovering in the mid-30s. Officials credit this partly to aggressive cougar-hunting that has depressed the local cat population and given the caribou some breathing room.
To be sure, there are other big stresses on the caribou too. Most notably, winter recreation, especially motorized recreation such as snowmobiling, can disturb caribou and force them to burn precious wintertime calories. In BC, other forms of recreation–heli-skiing and snow-cat skiing, in particular–appear to be accomplishing much the same thing for caribou populations. Experts even think that backcountry skiers may stress the animals.
The future of the Selkirk herd is very much in doubt. Without further augmentation, the herd is unlikely to survive. Fortunately, BC is planning to transplant 60 new animals to the herd over the next 6 years. (It was supposed to start this year, but was delayed.) If predation stays low and human impacts are minimized, the Selkirk caribou may yet have a chance at surviving, in the short-term.
Over the long-term, the only chance for caribou to inhabit the lower 48 will be improved habitat and more of it. That means strict conservation for old-growth forests and careful conservation and restoration in areas that can return to old forest conditions. One excellent way to begin this task–and also reduce human stresses–would be to expand Washington’s Salmo-Priest Wilderness, at the heart of the Selkirk herd range. There’s a 17,585-acre roadless area in Idaho’s national forestland, adjacent to the wilderness, that is ripe for inclusion and the stricter management that would bring.