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Woodland Caribou (Rangifer Tarandus Caribou)

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COSEWIC
Executive Summary

Woodland Caribou
Rangifer Tarandus Caribou

Species Information

Woodland caribou (Rangifer tarandus caribou) are medium-sized (100‑250 kg) members of the deer family. The taxonomy (classification) and systematics (evolutionary history) of caribou in Canada are uncertain. Based on mitochondrial DNA, caribou in North America evolved from two founding groups (clades) that differentiated in isolation during the last (Wisconsinan) glaciation. The southern clade supposedly evolved south of the continental ice sheet, whereas the northern clade was in a glacial refugium in Alaska and adjacent Arctic Canada. Populations that contained unique southern gene types were the Pukaskwa local population in Ontario and two in Newfoundland. In contrast, exclusively northern types occurred in four Yukon populations and in some forest-tundra and tundra ecotypes of barren-ground caribou (R. t. groenlandicus) in northern Canada. Most woodland caribou populations in the mountains of southern British Columbia (B.C.) and Alberta and in the boreal forest and taiga across Canada are mixtures of the two types. Some ‘mixed’ populations in the taiga exhibit two phenotypes and behave like the forest-tundra ecotype of barren-ground caribou.

Despite the recent genetic findings, no official change has occurred in the taxonomy of caribou. For example, all caribou in Quebec and Labrador and on the Hudson Plain are still considered woodland caribou. One strategy at the national scale is to protect geographic populations of caribou within National Ecological Areas (NEA) established in 1994 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Those areas were established for all species and are not a perfect fit for ecotypes of caribou in Canada. Consequently, it is necessary to exclude the forest-tundra (migratory) ecotype of caribou from forest-dwelling (sedentary) local populations within the Boreal NEA because of differences in genetics, ecology, demographics, and degree of habitat alteration through human activities.

Distribution

In this report, distribution of extant forest-dwelling woodland caribou is described for four National Ecological Areas (NEA) adopted by COSEWIC in 1994. They are Northern Mountain, Southern Mountain, Boreal, and Atlantic. Four COSEWIC populations of forest-dwelling caribou are named after corresponding NEAs. The insular Newfoundland population is removed from the Boreal NEA and treated separately.

The present distribution of woodland caribou in Canada, and adjacent southern Alaska and northern Idaho, is much reduced from historical accounts. The extent of occurrence in B.C. and Ontario decreased by up to 40% in the 19th and 20th century. Further range reductions are expected across Canada, particularly in southern parts of the current distribution. Within the general extent of occurrence, more than 164 areas of occupation now are mapped. Many are viewed as discrete local populations because radio-collared or marked caribou remained within mapped distributions. Some local populations are grouped into metapopulations based on an assumption that some emigration/immigration occurs among them.

This report includes only relatively sedentary woodland caribou located in the boreal forest and mountains of Canada, referred to as forest-dwelling caribou. Excluded are forest-tundra migratory ecotypes such as the George and Leaf River populations in Quebec-Labrador and several local populations on the Hudson Plains in Manitoba and Ontario. They are ecologically distinct populations. Also excluded is Dawson’s caribou (R. t. dawsoni), a woodland form that became extinct about 1935 on the island of Haida Gwaii (Queen Charlotte Island).

Habitat

Forest-dwelling woodland caribou occupy cover types that vary from coniferous forests to alpine tundra. In summer, they frequent open or semi-open habitat such as alpine tundra, upper subalpine, peatlands, islands, and shorelines where nutritious plants such as forbs and sedges are available. Spruce (Picea spp.) and pine (Pinus spp.) are usually the dominant trees in forested habitats. Balsam fir (Abies balsamea) occurs in mature and old forests. Tamarack (Larix laricina) is a common tree species in fens. The niche of forest-dwelling caribou is lichen-rich mature and old coniferous forest in a matrix with one or more of alpine/subalpine, subarctic (taiga), peatlands, or lakeshore. There is little overlap with preferred habitats of other large ungulates. Lichen species preferred by caribou are a consistent feature of winter and summer home ranges. Where snow is relatively shallow, caribou paw to uncover terrestrial lichens. Where snow is deep and compacted, such as in the southern Cordilleran Mountains, they eat arboreal lichens. Lichens tend to be most abundant in mature and old forests, consequently fire and logging can displace caribou for decades. Forest-dwelling woodland caribou occur at low density and therefore require large areas with specific habitats for foraging, calving, and avoiding predators. Densities from the Cordilleran Mountains to Labrador often are in the range of 1-4 caribou/100 km2.

Biology

Woodland caribou breed in late-September and October. Most adult (>1 year) females produce one calf in May or early June. The females disperse to calve individually in forests, peatlands, islands, lakeshores, and tundra thereby reducing predation. Death of calves in the first month generally is high and mortality before 1 year usually is 50-80%. Some forest-dwelling caribou migrate short distances (<100 km) between winter and summer ranges. Others are relatively sedentary or they seasonally shift between winter and summer range and periodically change wintering locations because of unfavorable snow conditions or habitat disturbance.

Population Sizes and Trends

The Canadian population of forest-dwelling woodland caribou in 2000/2002 is estimated at 184 000. Excluded are up to 1.1 million caribou of the forest-tundra ecotype, most of them in Quebec and Labrador. About 78% of forest-dwelling caribou occur in insular Newfoundland and the Northern Mountain NEA. Their exclusion leaves only about 40 000 caribou distributed across a huge area of the southern Cordilleran Mountains, boreal plains and shield. Those caribou are most at risk from accelerated development and associated increases in abundance of ungulate species and their predators.

Population numbers of forest-dwelling caribou appear to have increased in most COSEWIC NEA since the last status report in 1984. Except for insular Newfoundland, that increase is a result of improved surveys. A good index of the state of knowledge of forest-dwelling caribou is the number of identified local populations -- about 55 in 1984, 98 in 1991, and more than 164 in 2001. Numbers have increased sharply in insular Newfoundland, whereas decreases have occurred in many local populations in southern portions of the range across Canada. Much of the concern for the Southern Mountain and Boreal populations centres on direct and indirect effects of accelerated development resulting in small population numbers, small ranges (Southern Mountain), and increasing fragmentation and isolation. Average densities per 100 km2 vary from 150 on insular Newfoundland to 20 in Gaspésie Park, 11 in the Northern Mountain population, 5 in the Southern Mountain population, and about 2 in the Boreal population. It is doubtful that caribou can persist in forests managed primarily for fibre production.

Limiting Factors and Threats

A summary of threats to four COSEWIC populations reveals that predation and effects of developments are paramount for the Southern Mountain and Boreal populations. Predation and hunting are the main proximate causes of mortality in forest-dwelling caribou. However, increased mortality usually is precipitated by changes in habitat and weather. Predation rate often is linked to factors such as weather, habitat disturbance, occurrence of alternative prey, and trails and roads that facilitate access by predators to caribou habitat. Caribou populations that increased in the 1990s are those where habitats remain relatively pristine and wolves are absent (insular Newfoundland) or at low densities (parts of taiga range).

Habitat changes that favour increases in deer (Odocoileus spp.), moose (Alces alces), and wapiti (elk) (Cervus elaphus) can result in greater predation on forest-dwelling caribou. Loss and degradation of habitat because of fire, logging, and other developments impact forest-dwelling caribou populations across Canada. Local populations associated with alpine, taiga, and large peatland complexes have the best prospect for survival. Local populations on the southern periphery of the range are vulnerable to the potential effects of climatic warming such as more snow with greater crusting, more area burned in the west, and more and different predators, insects, and disease. Caribou may tolerate limited development if adequate habitat is maintained, predators are managed directly or through management of alternative prey, and hunting is reduced through co-operation with Aboriginal groups. Conservation of declining populations of forest-dwelling caribou will require careful management of a web of interacting factors. More monitoring and research of caribou populations is needed to clarify ecological relationships and responses to developments. Population indicators need to be refined and new ones developed.

Special Significance of the Species

The subspecies caribou is virtually endemic to Canada. Conservation of caribou populations is necessary to maintain biodiversity in coniferous forests across Canada and in the subalpine and alpine ecoregions of the Cordilleran Mountains. Loss of local populations would impoverish biological diversity in all landscapes occupied by caribou. Caribou have symbolic value to Canadians, particularly to Aboriginal groups that co-existed with caribou for centuries. They are a symbol of wilderness areas and are almost mystical because most Canadians have never seen one.

Existing Protection or Other Status Designations

Protective measures include protected areas; legislation pertaining to species at risk, developments, and hunting; guidelines for caribou protection when developments occur on caribou range; agreements with Aboriginal people concerning caribou hunting; and societal attitudes and ethics. Many local populations are located partly in protected areas such as parks and wilderness areas. Recreational hunting is banned or not a factor. At-risk designations highlight concern for caribou in parts of Canada. Western woodland caribou were listed as rare by COSEWIC in 1984 and vulnerable in 1995.

Summary of Status Report

Forestry and other developments in the Northern Mountain population are beginning to affect a few local populations of caribou. However, the habitat is little changed in remote areas of occupation. Variable weather, changing predator-prey relationships, and greater access by unregulated hunters affect numbers in local populations.

Local populations in the Southern Mountain population are generally small, increasingly isolated, and subject to multiple developments. The range has shrunk by up to 40% and almost half of the local populations (12-14/30) are decreasing in number. Local populations at the southern limit of the distribution (Selkirk, South Purcells, and Banff) and other small, isolated populations (Barkerville, George Mountain, and Telkwa) are likely to disappear. The outlook for habitat quantity and quality and predator management is not favourable. 

In the Boreal population, numbers have decreased during recent studies in a majority of local populations where trend data are available (12/1). Decreases may also occur in 65% of the range where no trend data are available. There is a high proportion of small local populations in small ranges at low density. Area of occupancy has shrunk up to 40% in Alberta and Ontario. Several small subpopulations at the southern periphery of the extent of occurrence have disappeared in the past 20 years. Caribou populations in commercial forests are most at risk from habitat loss and degradation, accelerated habitat fragmentation, and increased predation caused indirectly by increased numbers of deer, moose, and elk. Much of the range is in the commercial forest and some of it is in areas with high oil and gas activity. Ranges of some local populations in the commercial forest will decline sharply in quantity and quality as forestry and other developments expand.

The Atlantic (Gaspésie) population is an isolated relic population of caribou that formerly ranged into the Maritime provinces and northeastern U.S.A. Although numbers have varied from 150 to 250 individuals over the past 20 years, it is subject to genetic drift, inbreeding depression, and chance catastrophic events.