Caribou, also known as reindeer in Eurasia, are iconic mammals of the Arctic and sub-Arctic regions, known for their extensive migrations. These animals, belonging to the species Rangifer tarandus, rely heavily on specific habitat features for their survival. Understanding the intricate relationship between caribou and their environment is paramount, as their continued existence is inextricably linked to the health and integrity of their northern homes. Caribou thrive in harsh conditions, making their habitat ecologically important.
Geographic Distribution of Caribou
Caribou exhibit a circumpolar distribution across North America, Greenland, and Eurasia. In North America, they are primarily found throughout Canada’s boreal region and Alaska, inhabiting tundras, boreal forests, and mountainous areas. While some caribou populations are found as far south as 46° North latitude, others, like the Peary caribou, extend northward to 80° North latitude.
Various subspecies, such as barren-ground, woodland, and mountain caribou, occupy distinct regions. Barren-ground caribou are primarily found on the tundra from Alaska to Baffin Island. Woodland caribou are found in the boreal forests across Canada, from British Columbia to Newfoundland and Labrador.
Key Caribou Habitat Characteristics
Caribou habitat is defined by vegetation and terrain features. Lichens, particularly arboreal and terrestrial forms like Bryoria spp. and “reindeer moss,” constitute a primary winter food source for survival. During the summer, their diet diversifies to include a variety of grasses, sedges, mosses, shrubs, and forbs.
The terrain plays a role, with open tundra, boreal forests, and mountainous regions providing different resources. Open alpine or subalpine habitats are often used during the rutting season in October, while low elevation forested winter ranges occur in specific biogeoclimatic zones. Snow conditions, including depth and hardness, are also important, influencing their movement and ability to access buried food. Their large, concave hooves are adapted for snow and soft tundra, and also function as scoops to uncover lichens.
Seasonal Habitat Use and Migration
Caribou use their habitat throughout the year, driven by seasonal changes in food availability, predator avoidance, and reproductive needs. Many herds undertake extensive migrations, covering vast distances annually between winter and summer grounds. Spring migration, often led by pregnant females, occurs during April and May, with individuals traveling 7–24 km per day to reach calving grounds.
Summer ranges are characterized by rich vegetation and cooler areas, which also offer relief from insect harassment. After calving, caribou often form large aggregations to minimize disturbance from insects. Winter ranges are selected for accessible lichens and shelter from harsh weather. While some herds migrate along predictable routes, others, like sedentary caribou, may exhibit elevational migrations, moving to lower altitudes in winter.
Threats to Caribou Habitat
Caribou habitat faces numerous threats. Climate change is a significant factor, leading to altered snow and ice conditions, which can make it difficult for caribou to access lichens, their primary winter food source, when rain falls on snow and creates ice layers. Warmer summers and fewer snow patches can also increase insect harassment, reducing feeding time and impacting calf growth. Wildfires, which are projected to increase with warmer, drier conditions, can devastate lichen-rich areas, with recovery taking decades.
Habitat fragmentation and loss are exacerbated by industrial development, including oil and gas exploration, mining, forestry, and road construction. These activities create linear corridors that predators like wolves can use to access caribou more easily, increasing predation risk. The expansion of species like white-tailed deer into caribou habitat due to warming temperatures also attracts more predators, indirectly impacting caribou populations. This cumulative effect of habitat alteration, both natural and human-caused, impacts the availability and quality of essential caribou habitat elements.
Conserving Caribou Habitat
Efforts to conserve caribou habitat involve protection, restoration, and collaborative management. The establishment and expansion of protected areas, such as the Klinse-za/Twin Sisters protected area in British Columbia, play a role in providing refuge for endangered caribou and other species. This expansion, increasing the park to over 200,000 hectares, demonstrates a commitment to safeguarding large tracts of undisturbed habitat.
Land use planning is another strategy, aiming to minimize the impacts of industrial development within caribou ranges. This includes developing operating guidelines for activities like forest harvesting and resource extraction to protect key areas. Restoration efforts focus on reclaiming degraded habitats, such as restoring industrial landscape features like roads and seismic lines. Collaborative initiatives involving governments, Indigenous communities, and environmental organizations are undertaken, integrating traditional knowledge with scientific research to inform conservation strategies and promote stewardship of caribou habitats.