Northern Mountain Caribou

Northern mountain caribou are a subspecies of the woodland caribou (Rangifer tarandus caribou) and are found in the Northwest Territories, the Yukon Territory and British Columbia. They are the largest subspecies of caribou in the NWT. Current estimates put their population at about 21,800 individuals, but exact numbers are not known. There are three subpopulations: Redstone, Bonnet Plume, and Nahanni Complex. The Nahanni Complex includes La Biche, South Nahanni, and Coal River. The Redstone, Bonnet Plume, and Nahanni Complex subpopulations vary in numbers with estimates of 10,000, 5,000, and 3,000 individuals, respectively. 

Biology

Northern mountain caribou often have a distinct white neck, mane, underbelly, and rump. They also have a patch above each hoof that is a cream colour. The rest of their coat is brown in the summer and a greyish colour in the winter. They have semi-hollow guard hairs that overlay a dense undercoat which acts as insulation against cold weather and provides buoyancy for swimming. They have long legs that allow them to move through snow efficiently and have large hooves that allow them to walk on the snow. Their hooves are broad and have sharp edges to break and clear snow so they can access lichen. The scoop shape of their feet allows for paddling when swimming. Their hooves are worn down by walking on hard ground and rocks during the summer but grow long in the winter. They have scent glands at the base of their ankle that releases a scent when they are startled in order to warn others nearby of danger. Their weight is between 110 and 210 kgs, and their height at shoulder is 1-1.2m. Adult bulls will shed their antlers early on in the winter, while cows keep theirs until calving ends in June, so they are able to fight for the best breeding grounds. Northern mountain caribou can look very similar to their cousin- the barren-ground caribou. However, northern mountain caribou are larger, darker, have thicker and broader antlers, longer legs and a longer face. 

Northern mountain caribou typically breed in late September/October and calf in late May/early June. The pregnancy rate of northern mountain caribou can be over 90%, but calf survival rate can be only 50% or less. It is thought that calf survival rate increases as the quality of calving ground increases. Calving is known to occur in high elevations and mountainous terrain, which helps provide protection from predators and refuge from insects. Northern mountain caribou usually have one calf each spring, and typically don’t start breeding until they are at least two years old. 

Habitat

Northern mountain caribou are found in the Dehcho, Sahtú and Gwich’in Regions. They live in the Mackenzie Mountains and are primarily migratory, however there are some sub-populations that are non-migratory. They migrate seasonally and in elevation in the spring to reach calving areas and in late summer to early fall in response to availability of resources and to avoid predators. This allows them to make use of high-quality habitat, access forage rich areas, reduce predation risk and utilize seasonal resources. Seasonal migration can gather groups of tens and hundreds to thousands. Summer habitat includes open alpine and subalpine areas which often have ice patch habitat that is a refuge from insects and heat. Winter habitat includes old growth conifer forests at low elevations, montane spruce-lichen forests, and windswept alpine forests. They are reliant on old growth forests because they have abundant amounts of terrestrial and arboreal lichen, and shallow snow depth due to interception by the canopy. Windswept areas have shallow snow due to the wind, which allows access to terrestrial lichen. Winter habitat is often in areas where a rain or snow shadow is present, which results in reduced precipitation. Terrestrial lichen is known to thrive in these areas as they have the ideal soil and fire regime. Northern mountain caribou need a large area of undisturbed old growth woodland for food and protection from predators. Industrial development such as roads, powerlines or buildings have been known to be avoided by caribou especially females with calves. This can limit their seasonal migration from winter to summer habitat, cutting them off from suitable calving grounds and forage. Habitat is protected within Nahanni and Naats’ihch’oh National Park Reserves, however these areas do not fully protect the seasonal variation of habitat necessary to sustain many of the subpopulations that move in and out of the National Park Reserves. 

Diet

Lichen is their main diet in the winter- they break through the snow with their hooves to access and eat terrestrial lichen. When the snow is thick and strong enough to support them, they enter mature coniferous forests to eat arboreal lichen such as old mans beard or witchs hair. As the snow melts, they primarily eat sedges, new leaves and flowers in wetlands and valleys. They have also been known to eat grasses, forbs, and fungi.

Threats

Disruption of access to seasonal habitat and habitat loss is a significant threat to northern mountain caribou. This can be caused by industrial activity, roadbuilding, forestry, mineral exploration, recreational activity, and climate change. Many of these activities are accepted land uses but if they are not managed to reduce cumulative effects, consequences for mountain caribou can be severe including the loss of herds. This is occurring frequently among the southern mountain caribou population. Some of the documented behavioural responses to habitat disturbance and development include: 

Males and females have been known to avoid areas that have roads, powerlines, or industrial development therefore cutting them off from suitable habitat and limiting their ability to migrate from winter to summer habitat. Female caribou with calves are especially likely to avoid areas with development. They are at risk of  losing access to safe calving grounds, adequate food, or escape from insects. Avoidance of areas that have been anthropogenically altered can lead to a decrease in caribou population size because they are forced to use less adequate habitat. An increase of industrial activity can also increase access into caribous’ range, which can lead to an increase in hunting pressure, potential vehicle collisions and earlier access by predators. While some of the northern mountain caribou habitat is protected within Nahanni and Naats’ihch’oh National Park Reserves, many of the caribou move in and out of the parks. Decisions that are made outside of the park boundaries will also determine the future of these caribou. Predators of northern mountain caribou are mainly wolves and bears, but can also include coyotes, cougars, wolverines, lynx and golden eagles. Predation is part of a healthy ecosystem, but the predator-prey dynamic can be altered due to habitat loss and increased access into caribou range.  

Migration is intrinsically tied to food availability- the caribou move as plants grow and become available as a food source. As climate change alters the weather patterns in the NWT, the timing of food availability could shift in ways that no longer line up with caribou migration. Without access to an abundant food source, the caribou may not be able to regain the proper amount of weight needed for overwintering and could impact conception rates and calf survival. Climate change is also causing an earlier emergence and increased number of insects which can cause an increased expense of energy during foraging which may also make caribou more susceptible to predation. An increase in the frequency and intensity of extreme weather events is expected to occur in the NWT as a result of climate change. These weather events can cause large amounts of snow or freezing rain storms which renders food beneath the snow inaccessible to the caribou. Climate change is also resulting in tree line expansion which limits habitat and results in a loss of patch ice. The caribou are reliant on patch ice habitat for refuge from insects and heat.

Current Action

Federally, northern mountain caribou were assessed as special concern by COSEWIC and listed as special concern by the Federal Species at Risk Act. In 2012 a national management plan for the northern mountain caribou was released by the federal government and can be read about here. In NWT they were assessed as special concern by the Northwest Territories Species at Risk Committee and are under consideration to be listed as special concern by the Northwest Territories List of Species at Risk. In 2020 the Northwest Territories Species at Risk Committee released a Species Status Report for the northern mountain caribou. This was used to recommend the designation of special concern to the Northwest Territories List of Species at Risk. The northern mountain caribou range that falls within Nahanni and Naats’ihch’oh National Park Reserve is protected.