Barren Ground Caribou

kj-lBarren Ground Caribou (Rangifer tarandus granti) are found throughout the Arctic. There are two herds of caribou that live on ANWR. One is the Porcupine herd and the other is the Central Arctic herd. They have separate calving grounds and share the same range in summer and fall. The Central Arctic is an off chute of the Porcupine and both can be found in the same GUA. The Porcupine herd is estimated around 100,000 in population. The Central Arctic population is estimated around 30,000. Caribou populations fluctuate constantly.

Caribou are a member of the deer family and they share common traits. Arctic caribou are generally smaller in body size than caribou of the interior and Alaska Peninsula. Bulls will stand roughly 4 feet high and weigh approximately 400lbs at maturity. They will live to 8 years of age. Cows will weigh approximately half the bull’s weight, 225lbs and live a little longer.

Caribou will feed on grasses, sedges, willow, lichen, shrubs and other tundra plants. They will be on the constant move to elude predators and search for good feed. They also have four stomachs and will chew their cud while traveling or bedded.

Calves will be born in May most likely along the coastal plains and foothills of the Beaufort Sea. Cows usually bread in their 2nd year and have one calf yearly. After calving they will gather in large nursery herds to avoid predators and biting insects. In these areas there will be grizzlies and wolves trying to get newborn calves. The bulls will move inland into the mountains to avoid insects. Dry windblown ridges seem to be favored to help shield warm temperatures and insects. As temperatures cool in early fall the caribou will move through the Brooks Range. They will be on the constant move and start to gather in larger herds and begin to get a flow to their movement. The bulls will shed velvet in September and start to rut. Bulls will breed cows that are in their area and they will fight to control their area. In this time bulls will burn lots of calories and feed little. They will use a lot of their fat build up from summer. Bulls will shed their antlers in early winter. The migration will start as their feed gets harder to access with colder weather and winter storms. The Porcupine herd usually migrates through the Brooks, south toward Arctic Village and into Canada. They seem to make a loop and return to the Arctic coast to calf in the spring. Year to year these migratory routes will change but the flow is fairly consistent.

Arctic bull’s antlers vary in configuration. Hunters should expect to shoot a mature bull if the opportunity exists scoring 375” B&C. We have harvested many book bulls over the years. Cows will also have antlers but will not shed them when pregnant with a calf because they use them for protection against predators. Cow antlers grow to approximately 18” in height.

I believe the location of caribou dictates where the high numbers of predators are found in the arctic. If the caribou have calved and stayed at the base of the range to feed through late spring and early summer the wolves and bears will be more highly concentrated in these areas that season due to the young calves and abundant food source. The grizzly population seems to be strong and unchanged over the years.

Like antlered gypsies, barren ground caribou are always on the move. Exactly when and where they go is impossible to predict. Most herds, however, are drawn to a specific calving area. Named for the major river within its range, the Porcupine Caribou herd uses an area the size of Wyoming in the Refuge and the Yukon and Northwest Territories. The animals winter in the southern portion of their range, including the Refuge, where they are an important resource for the Gwich’in people. Sometime in April, the caribou head north toward the traditional calving grounds on the arctic coastal plain, 400 miles away. The route they take depends on snow and weather conditions. The caribou are a vital part of the natural system that operates there. Unalterably linked to the area, the herd both depends on and enhances the dynamic wilderness that is the Arctic Refuge.

As its name suggests, the Central Arctic Caribou herd roams the central region of northern Alaska. Smaller than the Porcupine Caribou herd, which travels throughout the Arctic National Wildlife Refuge, the Central Arctic herd (estimated at 70,000 in 2010) was once thought to be part of the Western Arctic Caribou herd, but is now recognized as a distinct herd. Caribou herds are identified by where females within the herd give birth to their calves. The female caribou of the Central Arctic herd calve across a broad swath of the Arctic coastal plain from the Canning River drainage of the Arctic Refuge west to the Colville River. Most calves are born in areas on either side of the Prudhoe Bay oil complex.

Soon after calving season, Central Arctic herd caribou move outward both east and west to their summer range, which extends from the 1002 Area of the Arctic Refuge well west beyond Prudhoe Bay. In the fall, many of these caribou migrate south through the Brooks Range mountains to spend the winter along south slope river drainages deep within the Arctic Refuge. Some members of the herd, however, remain on their summer range north of the mountains throughout the year, seeking out wind-blown valleys and tundra benches to find the lichens they need in order to survive the long, cold winters.

Central Arctic herd animals that winter near Arctic Village, just beyond Arctic Refuge’s southern boundary, are an important subsistence resource for the people living in that community. These villagers harvest caribou for food throughout the winter. The herd is also hunted on its coastal summer range by villagers traveling by boat from Kaktovik. The Central Arctic herd has increased in numbers over the past 10 years, ensuring hunters that caribou are available in adequate numbers to supply villagers with this sustaining bounty.

 

Caribou and the Coastal Plain

caribou3The coastal plain comprises only 10 percent of the Arctic Refuge. Yet from May to July, it is the center of biological activity on the Refuge. For centuries, animals from the Porcupine caribou herd have used the coastal tundra to calve, obtain nourishment, avoid insects, and escape predators.

The calving grounds of the Porcupine caribou herd include the northern foothills of the Brooks Range and the arctic coastal plain from the Tamayariak River in Alaska to the Babbage River in Canada. The most often used calving area, however, is on the Refuge coastal plain between the Katakturuk and Kongakut Rivers. Commonly, one-half to three quarters or more of the calves are born within this area.

The Refuge coastal plain is very important to calving success and calf survival in the Porcupine caribou herd. There are two main reasons for this. First, fewer brown bears, wolves, and golden eagles live on the coastal plain than in the adjacent foothills and mountains. As a result, the newborn calves have a better chance to survive their first week, until they become strong enough to outrun their pursuers.

The Refuge coastal plain also provides an abundance of plant species preferred by caribou. Nutrition is very important to the pregnant and nursing cows, particularly after the long winter. The timing of snow melt and plant “green up” on the coastal plain coincides with their calving period. This gives the new mothers access to the most nutritious food when it is most important for their health and the proper development of nursing calves.

The entire Porcupine caribou herd and up to a third of the Central Arctic herd use the Refuge coastal plain when calving is completed. This essential area contains forage and a variety of habitats that provide insect relief, including the coast, uplands, ice fields, rocky slopes, and gravel bars.

Their annual visit to the Refuge coastal plain brings new life and vitality to the caribou. It is an important part of their life cycle. The coastal plain provides the caribou vital nourishment and a better chance of avoiding predators and insects. This relationship is part of the unaltered system that makes the Arctic Refuge such a wondrous place.

 

Additional caribou south of the Brooks Range

In the fall of 2003, biologists estimated that a portion of the Porcupine Caribou herd (approximately 50,000 animals out of an estimated total of 123,000 at that time) settled into their wintering area around Arctic Village. As the winter progressed, these caribou were most often seen east of the village, but animals also wandered both north and south of the main group.

The Porcupine caribou had neighbors for the winter months, when most of the Central Arctic herd (approximately 25,000 animals out of an estimated total of 32,000 at that time) took up residence just to the west of Arctic Village. With so many animals from both herds wintering in this region, the Arctic Refuge supported one of the largest winter concentrations of caribou in several years.

The Arctic is the best place to reliably harvest a trophy bull. The herds in the rest of the state are on a downward cycle and our population is strong. We look forward to offering caribou hunts on ANWR.

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