Woodland Caribou
Last Update/Review: June 17, 2002
Status | Description | Habits | Food | Limiting Factors | Management and Outlook
Status
Among
North American ungulates, the woodland caribou appears to be least
able to adapt to the magnitude of environmental changes associated
with agricultural, urban, and industrial development over the past
100 years. Caribou distribution has moved northward from southern habitat
limits. So, in 1984, the Committee on the Status of Endangered Wildlife
in Canada (COSEWIC) classified the western woodland caribou as rare.
Woodland caribou and their habitat are threatened in Alberta and the Wildlife Act lists them as an endangered species. These caribou are likely to become extirpated in Alberta if the factors causing their reduction in numbers are not reversed. Caribou distribution and numbers have declined since the turn of this century along the southern edge of their range where human encroachment has been greatest. There is little data on past and current population size of caribou in Alberta, but a recent assessment estimates that 3600 to 6700 caribou inhabit about 113 000 km² of northern and west central Alberta.
Description
The caribou is a member of the deer family. Only the woodland subspecies (Rangifer tarandus caribou) resides in Alberta. Both males and females grow antlers, but those of cows are shorter and have fewer points. Mature bulls grow large racks which they use during the breeding season (rut) to defend their group of cows from other bulls. The mature, breeding bulls drop their antlers in December, whereas young bulls usually retain their antlers until late winter. Cows drop their antlers during or just after calving.
Adult bulls can weigh up to 270 kg (600 lb.) but average about 180 kg (400 lb.), while cows average about 115 kg (250 lb.).
The caribou is a beautiful animal. In fall, their antlers have shed their velvet, and their summer coats are a rich dark brown on back, sides, legs and face, and creamy white at the neck. The white neck hair, or mane becomes more pronounced on a mature bull as its neck swells during the rut. The caribou's large feet with crescent-shaped hooves make travel easier in deep, soft snow or spongy moss bogs.
Behaviour
Migration
Woodland caribou are migratory but their movements are not as extensive
as those of the barren ground caribou (Rangifer tarandus groenlandicus).
In Alberta there are two ecotypes of woodland caribou that differ
primarily in their migration habits. The mountain ecotype of west-central
Alberta undertakes long migrations of 80 km or more (straight line
distance) between its forested foothills' winter range and mountainous
summer range. In contrast the boreal ecotype may carry out long or
short seasonal migrations (15 km to 80 km) but remains within forested
habitats throughout the year.
Breeding
woodland caribou breed in early to mid-October and the calves are usually
born between late May and early June. A cow does not mate or breed
until she is 2.5 years old, and will usually produce only one calf
a year. Caribou productivity is low compared to other members of
the deer family, which breed at a younger age and often produce twins.
Social Behaviour
The woodland caribou is primarily a social animal. However, the cows
calve alone while widely dispersed over their summer range. Caribou
form their largest groups during the breeding season and again in
late winter when food supplies are restricted.
Habits
Woodland caribou inhabit the boreal forest of northern Alberta and mixed coniferous forests and alpine regions of west-central Alberta. Pure pine, pine/black spruce forests and treed muskegs are the main habitats woodland caribou use in winter. During spring, summer and fall, mountain caribou use alpine snow beds, treeline habitat and subalpine forest. Woodland caribou in other areas of Alberta use open muskeg as well as mature coniferous forests spring through fall.
Food
Caribou are well-known for their ability to use ground and tree lichens as major food sources. As a result they are most often associated with mature coniferous forests that provide substantial quantities of either ground or tree lichens. It takes 80 to 150 years for a forest community to grow adequate amounts of lichen for caribou. Their winter diet is usually composed of 60% to 70% lichens, with shrubs and grasses comprising the majority of the balance. Caribou are highly tolerant of severe winters and snow depths in Alberta. They rarely limit their movements or feeding habits as long as the snow is soft. When snow becomes crusted or compacted, digging for ground lichens is very difficult. Tree lichens can then provide an adequate diet for most of the winter. Since slow-growing lichens form the bulk of their winter diet and snow conditions can vary from one winter to the next, caribou herds require large winter range. The summer diet is diverse with increased use of willow and forbs. Lichens, however, remain a major component often comprising 25% to 35% of their summer food.
Limiting Factors
In Alberta, the woodland caribou has been listed as endangered because its survival is in question. Understanding the factors that limit its existence is essential to developing strategies that ensure the long-term survival of this species. Caribou population growth is constantly affected by a variety of natural and human-caused factors, including predation, hunting, vehicle-kills, habitat change, disturbance, parasites and disease, and climate change. One of these factors is limiting if it prevents a caribou population from reaching the maximum size the habitat will support (carrying capacity). It is seldom the situation that a population increases or decreases in size due to one limiting factor alone and this is the case for caribou in Alberta.
The number of research studies of Alberta's woodland caribou populations has increased substantially in the past decade resulting in a greater understanding of the factors limiting population growth. In Alberta, scientists and managers agree that predation by wolves is the major cause of death of caribou that inhabit natural, undisturbed habitat. However, wolf predation is not so great as to cause a long-term decline of a caribou population. Caribou are distributed in their preferred habitats at low densities and this tendency in conjunction with a nomadic or migratory behaviour lessens the likelihood of excessive levels of wolf predation. But if this regime is disrupted by other factors such as habitat change or increased access, the influence of predation could increase significantly.
An adequate amount of suitable habitat is a key factor in maintaining viable caribou populations. Human use of caribou range can result in loss, fragmentation or alteration of important habitat elements, such as winter ranges, calving areas or migration routes. In Alberta, the main human activities that have and will continue to impact caribou range are timber harvesting, oil and gas exploration and development, coal mining and the proliferation of access that comes from all these industries. In the north, peat-land development to harvest peat moss has the potential to impact important caribou habitat.
All caribou range in west-central Alberta and most range in northern Alberta has been committed to timber harvesting through Forest Management Agreements or Quota Licences. Timber harvesting (or wildfire) removes large areas of mature and overmature coniferous forest, the preferred habitat of caribou. This loss of habitat can affect caribou at several levels:
- loss of the primary winter food (lichens),
- loss of closed canopy forest where snow interception makes travel and foraging more energy efficient, and
- an increase in the numbers and distribution of other ungulates such as moose, deer and elk which prefer young, regenerating forests.
This
latter effect can result in an increased level of predation on caribou
as wolf numbers increase in response to more plentiful prey. Even a
relatively small increase in predation rate, perhaps coupled with increased
losses to illegal hunting, can lead to population declines over the
long term.
Expansion of coal mining north of Grande Cache will remove alpine winter range and possibly disrupt seasonal movements of a mountain caribou herd. Oil and gas exploration and development generally do not result in much direct loss of habitat but the associated access can be a significant disturbance. Incremental increases in the abundance and quality of roads, pipelines, seismic lines and other access routes can harm caribou populations by increasing caribou mortality from increased hunting, vehicle collisions and predation, and by disrupting seasonal movements. Resource extraction activities generally result in new and upgraded access routes and increased use of existing routes. Human recreational activities, often associated with access routes, can also compromise caribou populations and the quality of caribou habitats.
Traditional movement patterns and an innate curiosity make caribou vulnerable to hunting. Even though recreational hunting of caribou is prohibited throughout Alberta, losses to illegal hunting or mistaken identity (caribou mistakenly shot as elk, moose and deer) continue. Legal harvest of caribou by Treaty Indians does occur, but with few statistics on the number of animals taken it is difficult to evaluate the significance of this factor.
Throughout Alberta's woodland caribou range, the main challenge involves the maintenance of sufficient habitat for caribou and other wildlife, while balancing the demand for jobs, products, and revenue that resource extraction industries provide.
Management and Outlook
It is not enough to simply classify woodland caribou as endangered. Significant changes are required in how we use the land on which caribou rely for their continued existence. But a single government agency or interest group cannot enforce these changes. So in 1994, Natural Resources Service convened a committee to develop a Provincial Woodland Caribou Conservation Strategy. This committee consisted of stakeholders representing a variety of industries, conservation groups, aboriginal groups, academics and government agencies. They produced a strategy document that identified and assessed the various factors (biological, social and economic) that may affect the health of caribou populations in Alberta. They developed solutions to deal with those factors, recommended specific actions to make the strategy effective, and outlined the consequences (positive and negative) of those actions. The effective partnerships, cooperation, and lines of communication that were developed among the stakeholders will be key to achieving the caribou population and habitat goals that the committee endorsed.
The
Caribou Conservation Strategy is provincial in scope, but a more specific
level of management is required. Presently, three regional caribou
management committees exist to develop management plans for caribou
in the northeastern, northwestern, and west-central regions of Alberta.
These committees are composed of government and industry representatives.
They develop guidelines for how industrial activity will be conducted
on caribou range and how adequate amounts of caribou habitat will be
maintained in the short and long term. They assess the effectiveness
of the guidelines and habitat supply analysis, determine what further
research or inventory is required, and develop a cost-sharing agreement
for the management of caribou and their habitat.
In the 1930s, caribou distribution extended as far south as Nordegg, Edson and Buck Lake in west-central Alberta and through the Swan Hills to the Saskatchewan border in northern Alberta. Their present day distribution has retreated northward in response to human settlement, agriculture and timber harvesting. This unique member of the deer family is an important component of mature coniferous forest ecosystems and its decline is an early warning that people's activities on the land may be too intrusive. Greater awareness of the problems facing Alberta's woodland caribou and cooperative efforts by government agencies and industries to resolve land use conflicts bode well for their long-term health and survival. Strong public support to maintain the diversity of wildlife and habitat in Alberta, even the rarely seen species in remote areas, has been an important component in ensuring that caribou are managed wisely and will continue to be in the future.
