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NWT Barren-ground Caribou (Rangifer taradus groenlandicus)
Barren-ground caribou management in the Northwest Territories: An Independant Peer Review
GNWT Management Response - Barren-ground Caribou Management in the NWT
A Review of Concerns Expressed by Outfitters Between 2003 and 2007 About the Bathurst and Ahiak Herds
Survey Confirms Continued Decline in Bathurst Caribou Herd - September 24, 2009
NWT Barren Ground Caribou Management Strategy
Description
| Barren-ground caribou adult males stand about 110 cm high at the shoulder. They weigh about 140 kg in the fall when they are in their prime, but only about 100 kg in November after a month of mating activity. |
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Caribou have long legs that end in large, broad, sharp-edged hooves. This adaptation enables caribou to dig craters through ice and snow to feed themselves during the winter months. As well, their hooves provide good support and traction when traveling over snow, ice or muskeg, allowing caribou to move quickly and escape being eaten by predators. In winter, the fleshy pads between their hooves shrink and the hair between their toes forms tufts that cover the pads. Caribou walk on the horny rims of their hooves and the hair protects the pads from contacting the frozen ground. |
Lichens are common in the Arctic and caribou are one of the few mammals adapted to feed on them. Caribou have a rumen (large stomach) that can digest lichens. They can also recycle urea, which is one of the products of protein digestion. The ability to breakdown urea reduces the amount of water caribou need to eliminate toxins from their body. This is an advantage during the winter months when water is scarce.
The caribou's coat varies in colour seasonally. Each year, caribou lose their coat during the summer moult. Adult males are the first to begin moulting in late June. Nursing cows have the greatest nutritional needs and complete their moult last. During the moult, hair falls out in large patches revealing a new coat. When the shedding is complete, caribou are dark brown with a distinctive white belly and white mane. Adult males also sport a white flank stripe and white socks above their hooves. Throughout the summer months, white-tipped guard hairs grow out turning the caribou a more uniform light brown colour by fall. The guard hairs are hollow and during the summer months give the caribou buoyancy, which is helpful as they swim across rivers and lakes. In the winter, the air cells in the guard hairs act as an insulating layer to conserve body heat, resulting in a coat that is exceptionally warm. Over the winter, the caribou’s coat fades to light beige.
| Caribou are the only species in which both males and females grow antlers. Females probably have antlers so they can defend their winter-feeding craters from other caribou. Barren-ground caribou have the largest antlers relative to body size. Bulls have large antlers to advertise their strength to other bulls and to the cows. The design of the antler branches makes the bulls look large from the side view, and they are prominently displayed during the rut. When threat displays escalate into a fight, bulls lower their heads and charge with their antlers. The antler branches grapple together as the bulls shove and push each other. Caribou calves have short spike antlers that increase in size and complexity each year until the animals are quite old. Older caribou have smaller antlers with fewer branches. |
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Antler growth is directly related to how well caribou are feeding. If food is restricted or low in nutrition, caribou grow smaller antlers. Antlers are shed and regrown each year. As the bone core of the antlers grows, it is covered with velvet. The velvet is skin richly supplied with nerves and blood vessels and densely covered by short hairs. As the antlers reach their full size in September, the velvet dries and falls off in strips aided by the caribou thrashing their antlers against bushes. Adult males may shed their antlers as early as November, just after the rut. Younger males and barren cows may retain their antlers until April, while pregnant females lose their antlers a few days after calving in June.
Barren-ground Caribou Distribution
In the NWT, barren-ground caribou range over the taiga forests and tundra of the mainland. They have the widest distribution and are by far the most abundant subspecies of caribou in the NWT. They also have the greatest cultural and economic importance. There are several distinct barren-ground caribou herds in the NWT:
Bathurst herd
Cape Bathurst herd
Bluenose-East herd
Bluenose-West herd
Beverly herd
As well, the Ahiak (Queen Maud Gulf) herd of Nunavut’s northeast mainland migrates southwest during the fall and has been known to winter on the tundra in the eastern NWT.
Behaviour
Caribou are generally silent animals except during the rut when bulls snort and grunt, and after calving when cows call to their calves in short grunts and the calves bleat to the cows. Cows and calves can recognize each other’s voice even in a mass of other cows and calves.
Caribou have several other characteristic sounds that are not vocal. The sharp clicking noise made by the movement of the tendons and bones just above the hooves can be heard most clearly on calm cold days as large groups of animals journey across the tundra. As well, the rattle and clash of antlers as bulls spar is commonly heard during the rut.
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Caribou walk at about 7 km/hr when migrating and can cover between 20 and 65 km a day. When startled, a caribou runs in a loose, even trot. The head is held high with the nose up and the tail erect. When galloping at top speed, most caribou can outrun wolves, their major predator. However, if a caribou hesitates, stumbles, or takes a wrong turn, wolves can quickly overtake an animal. |
Caribou are excellent swimmers. Although caribou normally select narrow stretches of water that are easy to cross, they can swim for long distances and have been observed crossing water bodies up to 10 km wide. Their hollow guard hairs help them float and their broad hooves propel them along at speeds of about 3 km/hr.
Annual Cycle
| The major barren-ground caribou herds in the Northwest Territories spend the winter in forested areas below the treeline. The exceptions are the Ahiak herd and Cape Bathurst herd which spend much of the winter on the tundra. In March and April, barren-ground caribou begin to move in a great northward migration. Individuals band together, each small group joining another, until long lines of caribou are moving steadily to their calving grounds, which may be as far as 700 km away. By the time the herds pass the last stunted trees of the northern forests and spread out over the still frozen barren-lands, they may number in the thousands. Pregnant cows lead the way and their urgency to reach the traditional calving ground is so great that nothing can hold them back. Even if calves are born along the way, they may be left behind as the cows continue on with the herd. |
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Bulls and immature caribou lag behind the cows and do not go all the way to the calving grounds. They leisurely graze their way northward following the retreating snow line, eating the nutritious new leaves sprouting on the sedges and willows, and waiting for the cows to return with the new calves. Many do not leave the forest until early June.
Calving grounds are often located in high, rocky areas, where there is little shelter from wind and driving snow. These conditions are favourable as they provide patches of bare ground that allow the cows to feed. If the spring snow melt is late and plants have not yet begun to grow, cows can continue to feed on lichens on the rocky slopes. If spring arrives early or on time, cows can feed on cotton-grass flower buds and green sedge leaves.
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Most calves are born within a few days of each other during the first two weeks of June and temperatures are usually near the freezing point. Calves can stand and suckle within a few minutes of birth. In an hour, a calf can follow its mother, and within a few days it can outrun a man. Maturing quickly helps newborn calves survive against predation from wolves and grizzly bears that are in the calving grounds. Most wolves remain within the treeline to den and are a reduced threat to cows and newborns at this time. As well, the high, rocky areas of the calving grounds are beyond the reach of most wolves that may pursue the hunt. These rocky slopes however, are home to grizzly bears that are quick to prey on newborn calves. |
As soon as calving is over, cows and calves slowly begin their long trek back toward the winter range. As spring turns into summer, the cows meet up with the bulls that have continued to drift north. In an attempt to reduce the intense disturbance caused by mosquitoes, warble flies and nose-bot flies, caribou form dense groups or "post-calving aggregations" that can number in the tens of thousands. They try to hide their faces, snort, stamp their legs, crowd together or gallop away to avoid the flies. Cooler temperatures and windy conditions can keep the flies grounded and provide some relief for the caribou. Because caribou are unable to feed when they are tightly packed together and they are shedding their winter coats, they look thin and ragged as they cross the summer tundra.
In August and September, insect disturbance decreases allowing caribou to focus on feeding. They break into smaller bands and slowly move across the tundra toward the treeline. They rapidly gain weight as they feed on mushrooms, lichens, shrubs and grasses. The cows, in particular, have to gain enough weight to be able to breed in the fall.
The rut occurs in October and is spectacular in its intensity. The bulls are in their prime with glossy new coats. Their antlers are polished and smooth from being scraped against shrubs and small trees. Their flowing white manes swing back and forth as they threaten and challenge each other. The rut may last for two or three weeks, however most cows bred within a few days of each other. By the time the rut is finished, winter has settled on the north.
The distribution of barren-ground caribou changes constantly during the winter as they search for places where the food is abundant and the snow is the shallowest. Caribou use their excellent sense of smell to lead them to lichens under the snow and their broad hooves are designed for digging feeding craters through snow and ice. Lichens are the mainstay of their winter diet, but sedges, and evergreen leaves are also eaten. When spring arrives the caribou once again begin their migration to the calving grounds. |
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Herds
Until the 1960s, barren-ground caribou herds were named based on where they wintered. Most aerial surveys estimated herd size based on the number of animals seen on late winter and spring migration ranges, even though the location of these ranges varied annually. Although calving grounds were known, they were not routinely surveyed to estimate caribou numbers until ear-tagging and field observations revealed that cows always returned to their traditional calving grounds. After that discovery, herds were named by the location of their calving areas.
Research in the 1990s provided evidence that barren-ground caribou belong to discrete herds. First, the use of satellite collars revealed that cows that calved together were also together during the rut (mating time). Second, DNA analysis indicated that the herds were genetically distinct from each other and probably have been for hundreds of years or longer.
Why caribou always return to the same general area to calve is uncertain but their traditions have held for hundreds of years. Referred to as the “traditional calving grounds”, this is the cumulative area, overlapping from year to year, that the cows return to annually for calving. Within these traditional calving grounds, a trend in the use of different areas may become apparent over time. For example, since the mid 1980s the Bathurst herd has calved consistently further west each year so that in 1996 the herd calved entirely west of Bathurst Inlet. Inuit elders recollect the same thing happened in the 1950s.
Predation by wolves and grizzly bears is the leading cause of caribou deaths. Each wolf can kill 15-30 caribou per year. The number of wolves in the ranges of the barren-ground caribou herds varies substantially over time. When wolf numbers are high, wolf predation will help determine if a herd increases or decreases. Recent studies have revealed that barren-ground grizzly bears are also effective predators on caribou, particularly in mid-summer prior to the ripening of berries on the tundra. Weather conditions can also affect herd numbers. Hot sunny summers can result in increased insect harassment and reduce time available for foraging while cool windy summers will allow caribou to maximize summer foraging time. Harsh winters can bring exceptionally deep snow or ice, making it difficult for caribou to feed. In the long run, forest fires maintain productivity of lichen ranges, but in the short-term these fires may alter the winter distribution of the herds, as caribou must search for available forage. Changes in the herd’s winter distribution can also change the availability of caribou to people who rely on caribou to meet their needs.
Management
The number of animals in a caribou herd naturally fluctuates over time. In the past, when caribou numbers declined, people starved unless they were able to meet their needs with other species. Caribou numbers will continue to fluctuate and not all herds will always be large enough to meet people's needs. Even though people will no longer starve when there is a shortage of caribou, declines will still bring economic and social hardships. The goal of caribou management is to manage human activities such that these activities do not cause herds to decline to the point where people do not have enough caribou or the herds are unable to recover from natural declines.
In 2000, the Bathurst Caribou Management Planning Committee was formed to address issues facing the Bathurst herd. Co-management processes have been established to provide input into how to manage human activities that affect caribou and their habitat. Each of the larger barren-ground caribou herds has a slightly different co-management process, but all have similar intentions. Using traditional knowledge and technical information, Aboriginal and government representatives work together to advise governments on management decisions affecting caribou.
For more information on each of the co-management boards:
Beverly and Qamanirjuaq Caribou Management Board
Gwich’in Renewable Resources Board
Porcupine Caribou Management Board
Sahtu Renewable Resources Board
Wek' èezhìi Renewable Resources Board
Wildlife Management Advisory Council (NWT)
In 2006 the Government of the Northwest Territories released a strategy to guide caribou management over the next four years
A management plan for the Bathurst caribou herd has also been developed. Interest in the Bathurst caribou herd grew in the 1990s with a surge in mining activities on the herd’s annual ranges. Since then, two diamond mines have been built on spring migration and post calving/summer ranges and a third diamond mine is under construction. The diamond mining companies monitor caribou abundance and behavior in the vicinity of the diamond mines, however uncertainties remain about the cumulative effects of the mines on the caribou.
Knowledge of caribou numbers is essential for management, but exact counts are neither possible nor necessary. For the larger herds, estimates of the number of pregnant cows on the calving ground can be used to determine whether a herd is stable, declining or increasing. However, calving ground estimates provide only a crude approximation of total herd size, as bulls do not migrate onto the calving grounds. A variety of methods are used to survey the herds, with each technique designed to fit the unique characteristics of the herd. Most surveys use aerial photography either during or after calving.
There are few restrictions on caribou hunting by Aboriginal people for their own use, but there are limits on the number of caribou from each herd that can be harvested for commercial sale. Resident hunters are allowed to hunt two caribou, male only, each year. Non-resident hunters may harvest a maximum of two barren-ground caribou and require a licensed outfitter.
Satellite-collared Caribou
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About Caribou Collaring
Since 1996, movements of barren-ground caribou cows have been tracked using satellite collars. Cows are collared during the winter and their movements are tracked by satellite throughout the year. The collars help us study seasonal range distribution, measure annual variations in rut and calving locations, and determine spring and fall migration routes. |
March 2006 Collaring - All herds
Radio collars were also placed on caribou in the Inuvik and Sahtu regions (Cape Bathurst, Bluenose West and Bluenose East winter ranges) so that the caribou from the three herds can be photographed and counted when they collect together after calving. The caribou within each herd collect together in large aggregations as a response to mosquito and warble fly harassment. The aggregations are easy to find if they include radio or satellite-collared individuals and once found, the aggregations are photographed from an aircraft and the individual caribou counted.
Biologists in the Inuvik, Sahtu and North Slave regions provide weekly maps that show the movements of the satellite-collared caribou. Check these sites regularly for updates.
Caribou have a high fidelity to calving, summer and fall ranges, however their winter ranges are known to vary annually. Satellite-collars have complemented earlier knowledge that there is overlap in the winter ranges used by neighbouring herds in some years.
How the cows are collared
Biologists use a helicopter to locate caribou as they migrate onto the tundra. Once a group of caribou is located, a net is fired from the helicopter to capture one of the animals.
Within seven minutes of capture, the caribou is collared and released back into the herd. The caribou’s eyes are covered during the collaring to help reduce stress during handling. This procedure requires no drugs and places the animal in very little danger.
Each collar is programmed to fall off the animal at a specified time. Once dropped to the ground, a satellite signal is used to locate the collar so it can be reused in future studies.
How caribou are tracked
The satellite collars turn on for six hours every five days. During this time, the transmitters send signals out into the atmosphere.
Four of the many satellites circling the Earth can pick up the signals from the collars. Each of these satellites passes within range of the collar transmitter at almost the same local time each day. If a collar is turned on while the satellite is sweeping that area for transmissions, the satellite picks up the signals and relays them to ground stations for processing. Our caribou data are relayed to one of the two ground stations in the United States.
The ground stations process the signals into longitude and latitude locations by measuring the Doppler shift on the transmitter signals. The Doppler effect is the change in frequency of the signal when a source of transmission (collar) and an observer (satellite) are in motion relative to each other. The ground station then emails the data to the caribou biologist.
During the six hours the collar is turned on, many location readings may be sent to the biologist from the ground station. The biologist plots maps according to the most accurate longitude and latitude signals sent from the collar. In ideal transmitting conditions, the accuracy of the coordinates can range from within 150 meters to up to 1000 meters from the actual location of the caribou.
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