Periodic Status Review for the Woodland Caribou (2023)

The South Selkirk subpopulation of Woodland Caribou (Rangifer tarandus caribou) was one of 17 herds of the Southern Group of the Southern Mountain Caribou or ‘Deep-snow Mountain Caribou’ ecotype. This subpopulation occurred in the southern Selkirk Mountains of southeastern British Columbia, northeastern Washington (in Pend Oreille County), and northern Idaho, and was the only remaining caribou herd that ranged into the contiguous U.S. The Southern Group/Deep-snow ecotype inhabits mountainous areas with deep snow accumulations and their winter diet is primarily arboreal hair lichens. They require large areas of old growth conifer forests throughout the year and migrate seasonally to different elevations and forest types to seek food and safe calving areas, and to avoid predators.

The South Selkirk subpopulation may have numbered in the hundreds in the late 1800s, but decreased to an estimated 25–100 caribou between 1925 and the mid-1980s. Numbers ranged between 33 and 51 animals from 1991 to 2009 despite being supplemented with 103 caribou during two multi-year translocations in the late 1980s and 1990s. Additionally, the South Selkirk subpopulation became isolated from neighboring subpopulations by human activities and development, and likely had no immigration occurring in recent decades. The subpopulation declined rapidly from 46 in 2009 to 1 animal in 2018. With the South Selkirk subpopulation facing imminent extinction, the last remaining South Selkirk animal was translocated to a pen located north of Revelstoke, B.C., and was subsequently released to join the North Columbia subpopulation in April 2019, marking the extirpation of caribou in the South Selkirks. Overall abundance of Deep-snow Mountain Caribou has declined 45% since the late 1980s; of the 17 herds, six are extirpated and five have fewer than 50 animals, and they totaled about 1,250 in 2021.

Timber harvest converted much of the mid-elevation old-growth forests to younger age that brought higher densities of deer, moose, and elk. Roads and abundant prey brought predators (i.e., cougars, bears, and wolves), into closer proximity and more frequent contact with caribou, resulting in an unsustainable frequency of predation. Predation was considered the most important proximate factor in the extirpation of the South Selkirk subpopulation. Other threats to the subpopulation were small size and isolation of populations, highway collisions, human disturbance associated with winter backcountry recreation that affected habitat use and movements, and climate change.

In the future, caribou could re-establish in Washington with positive, sustained recovery progress in Canada. Barring that, caribou are unlikely to re-establish in Washington without assisted reintroduction and a feasibility assessment that considers and proposes solutions to habitat and predation issues. It is recommended that Woodland Caribou remain listed as a state endangered species in Washington.