NWT Woodland Caribou (Rangifer tarandus caribou)
Boreal population / Northern Mountain population
Boreal Caribou Northern Mountain Caribou
Species at Risk (NWT) Act list: No status Species at Risk (NWT) Act list: No status
Federal Species at Risk Act list: Threatened Federal Species at Risk Act list: Special Concern
COSEWIC Assessment: Threatened COSEWIC Assessment: Special Concern
NWT General Status Rank: Sensitive NWT General Status Rank: Secure
Background and Description
| There are several subspecies of caribou in the NWT, of which woodland caribou are the largest. Male woodland caribou in the NWT weigh an average of 150kg and can reach 1.2 m high at the shoulder. Their brown summer coat turns greyish in winter. In all seasons their neck, mane, underbelly, rump and a patch above each hoof is a creamy white. Caribou are the only members of the deer family (Cervidae) in which both males and females grow antlers. Males have massive antlers while those of females are much smaller. Generally, antlers of woodland caribou are thicker and broader compared to those of barren-ground caribou. Woodland caribou tend to spend the entire year within the forest rather than making the long migration across the tundra each year the way barren-ground caribou do. Woodland caribou are also well adapted to their northern environment. Like all caribou, their large, well-insulated hooves prevent sinking when traveling on wetlands and snow and are adapted for digging through snow for food. |
Photo by R. Popko, ENR
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In Canada, woodland caribou have been divided into five distinct populations depending on where and how they live: Boreal, Northern Mountain, Southern Mountain, Atlantic-Gaspésie and Newfoundland populations. The NWT is in the range of two of these populations, the Boreal population and the Northern Mountain population.
The Northern Mountain caribou herds in the NWT include the Redstone, South Nahanni and Bonnet Plume herds and possibly some others. Northern Mountain caribou occur in groups that may number in the thousands during late summer to late spring and have distinct seasonal migrations, including use of different elevations during the changing seasons. Boreal caribou are similar to the Northern Mountain caribou that live in the Mackenzie Mountains but have a different lifestyle. Boreal caribou live in the forests east of the Mackenzie Mountains, tend to live in small groups, prefer to stay within the forest most of the year, and do not migrate.
Distribution
Historically, woodland caribou were found throughout most of the boreal and sub-alpine forest of Canada. Today their range has been reduced across much of southern Canada. In the NWT, their range has remained relatively unchanged. The Northern Mountain population (shown in blue on the map) is found on the east slopes of the Mackenzie Mountains to the NWT-Yukon Border. The Boreal population (shown in green on the map) is primarily found in the NWT’s boreal forest between the Mackenzie Mountains and west to the Canadian Shield.
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NOTE: Distributions are approximate and not intended for legal use.
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Population Size and Trends
There is little information about historical populations of woodland caribou. In 1982, the woodland caribou population in Canada was estimated at 193 000 animals. Since then, there has been a downward trend in almost all populations across Canada. In the NWT however, the Boreal population of woodland caribou is not considered to be at risk and is estimated to be between 6000 and 7000 based on traditional knowledge and scientific studies. The Northern Mountain population of woodland caribou is made up of about 36 herds in the NWT, Yukon, and northern British Columbia. There are approximately 45,000 adult caribou within the range of Northern Mountain caribou however numbers in the NWT are unknown.
Habitat
Woodland caribou generally prefer mature or old growth coniferous forests associated with bogs, lakes, and rivers. These forests offer high concentrations of ground and tree lichens. In winter, woodland caribou tend to favour uplands, bogs and south facing slopes where the snow is not too deep. Their winter diet consists of up to 80 per cent ground and tree lichens. In summer, they prefer areas such as forest edges, marshes and meadows that provide the fresh green growth of flowering plants and grasses. Calving grounds are vital to the well being of all caribou populations. Some of the best-known woodland caribou calving areas in the NWT are islands off the northwest shore of Great Slave Lake, since these areas are relatively isolated and predator-free. Females migrate to these islands when there is still ice on the lake and swim back to shore a few weeks after calving.
Biology
Woodland caribou can live to be 15 years old. Most females begin breeding at 28 months. Males can breed as early as 18 to 20 months, but competition usually prevents them from breeding until their third or fourth year. In some populations, depending on the ratio of males to females, males form harems of 12-15 females. The breeding season, or rut, is usually in late September or early October. During the rut, males use their antlers in clashes to determine dominance. A single calf is usually born in May or early to mid-June.
Limiting Factors
Woodland caribou in the NWT are at the northern extent of their range. Wildlife species expanding their range northwards could bring unknown diseases or parasites to woodland caribou; however, effect of diseases, parasites, and insect harassment is currently unknown for woodland caribou. Over the past 10 years, heavy truck traffic has increased on NWT highways, including winter roads that might increase the number of deaths and injuries to caribou by collisions with vehicles.
We can also look at what has happened and is happening to woodland caribou in other parts of Canada to give us some idea of the current and potential threats to these caribou populations in the NWT. In Alberta, agriculture, timber harvesting and especially oil and gas development have resulted in vast habitat changes and loss of the northern boreal forest. These activities require trees to be removed, new roads built, and seismic lines and pipeline right-of-ways to be cleared. Also woodland caribou, particularly the Boreal population, using areas near roads and seismic lines are more vulnerable to harvest and predation. All of these types of activities are expected to increase in the NWT. Woodland caribou have always co-existed with predators. But cleared areas, especially long clearings like roads and seismic lines, make it easier for wolves and bears to travel through the forest and locate prey. Food attractants like commercial waste fish piles and remote garbage dumps may increase the number of predators in some areas and increase the risk of predators finding caribou.
Protection
Outside the NWT, declining numbers and habitat loss has meant that woodland caribou are no longer found in some areas where they used to live. COSEWIC assessed the Boreal population of woodland caribou as Threatened and Special Concern for the Northern Mountain population in 2002. This concern about Boreal and Northern Mountain caribou in much of Canada also led to Boreal caribou listed as Threatened and Northern Mountain listed as Special Concern under the federal Species at Risk Act in 2004. Boreal caribou are now protected on federal lands and a national Recovery Strategy is being developed to conserve and recover boreal caribou populations and their habitat across Canada.
In the NWT, a quota system helps protect woodland caribou from over-harvesting by non-Aboriginal people. The NWT has a harvest limit of one woodland caribou per year (either Boreal or Northern Mountain, but not both) for resident hunters; non-residents can only hunt woodland caribou in the Mackenzie Mountains. There is no limit or closed season for boreal caribou for Aboriginal hunters. We think the total woodland caribou harvest is low, but we don’t collect harvest information from all hunters so we cannot be certain.
Recovery
Under a draft national Recovery Strategy, the Department of Environment and Natural Resources has developed the Action Plan for Boreal Woodland Caribou Conservation in the Northwest Territories 2010-2015 which provides the general goals and direction for the conservation the Boreal Caribou in the NWT.
ENR biologists and wildlife co-management boards have already begun conservation and management activities on Boreal Caribou in the NWT:
• Boreal caribou distribution and habitat use was assessed in the northern Mackenzie River valley (Inuvik and Sahtu Regions) using a mixture of satellite radio collars and GPS-satellite radio collars. Boreal caribou habitat suitability maps are currently being developed for the Inuvik and Sahtu regions using resource selection functions. Inuvik and Sahtu studies were initiated in April 2002 and March 2003, respectively.
• Population trend (adult female survival and calf recruitment) is currently being monitored in the northern Mackenzie River valley using a mixture of conventional VHF collars, satellite radio collars and GPS-satellite radio collars. Study was initiated in March 2004.
• In the North Slave Region, a systematic aerial survey of grid blocks containing potential habitat in the Taiga Plain ecozone to provide baseline density and presence/absence information for boreal caribou was completed. This effort was followed-up with workshops in all the North Slave communities to collect local and traditional knowledge on boreal caribou extent of occurrence and area of occupancy along with priority habitat sites.
• Population trend (adult female survival and calf recruitment) is currently being monitored in an area to the west of Hay River using a minimum sample size of 30 conventional VHF collars. Boreal caribou distribution and habitat use will also be determined, and predicted boreal caribou habitat will be mapped using resource selection function. Study was initiated in March 2003.
• A combination of satellite, GPS and conventional VHF collars have been deployed throughout the Mackenzie Valley in the Dehcho region to assess boreal caribou distribution, daily/seasonal movements and home ranges, and population trend by measuring adult survival and calf recruitment. These data will be used to produce regional maps and as part of the territorial-wide maps of resource and habitat selection based upon RSF modeling. The study was initiated in 2004 with 10 collars deployed in the Trout Lake traditional areas and expanded to include traditional areas of Fort Simpson, Jean Marie River, Wrigley, Fort Liard, and Nahanni Butte through 2005-2006. Since the start of the program, 69 adult female boreal caribou have been equipped with collars. Since 2006 there has been an average of 30 active (satellite and GPS) collars on female caribou in the study. Seven GPS and one satellite collar were deployed in February 2009. Calving and late-winter surveys have been flown annually since 2006. Dehcho Boreal Caribou Study Progress Reports are available here.
• Baseline information on pregnancy rates, and parasites and disease is being collected in conjunction with studies that use radio collars in the Dehcho, Inuvik, Sahtu and South Slave regions.
• DNA material has been collected from the above collaring studies to quantify the genetic diversity within and gene flow amongst boreal caribou populations across the NWT.
• In September 2007, an NWT-wide analyses began using individual-based modeling to determine sustainable or unsustainable levels of impact, evaluate the response of boreal caribou to anthropogenic linear features in areas with varying levels of development impact (reduced use/avoidance), and evaluate range fidelity and reproductive performance of boreal caribou in areas with varying levels of development impact and predation risk. Throughout the NWT, a range-wide resource selection function or habitat selection model will examine the degree of fragmentation and connectivity of selected or preferred habitats.
• Wildlife survey (boreal caribou one of the specific target species) of the Sambaa K’e candidate protected area was completed in March 2009.
• Facilitated by the Gwich’in Renewable Resources Board, a Traditional Knowledge study was completed in the Gwich’in, Inuvialuit, and Sahtu land claim areas.
• Wek’èezhìi Renewable Resources Board will be engaging government partners in developing a comprehensive proposal for managing boreal caribou in the Wek’èezhìi area. The comprehensive proposal will be a process or framework for working together in management.