How do woodland caribou reproduce

This population continued to decline until , when only 26 caribou remained. Current estimates put their numbers at about 35 individuals without any increases for some time.

Fewer than 1, caribou survive north of the border in Canada. Caribou are the only deer in which both males and females have antlers, although only some females have them. When factors having negative effects on caribou births and deaths occur more frequently more bad years than good years , populations decline.

Caribou populations increase when the opposite occurs. Usually a combination of factors cause caribou numbers to change. Harsh weather can reduce plant growth, which causes poor caribou nutrition, and reduced survival. Some years, insect harassment interferes with caribou foraging, which also decreases survival. If it rains during the winter, ice can prevent caribou from getting their food. They may starve when this happens. Wolf populations in caribou winter ranges can increase in response to higher levels of other prey such as moose.

When caribou return to the winter range they are preyed on more heavily by the increased number of wolves. On the other hand, when arctic foxes reach a high in their population cycle, they sometimes spread rabies to neighboring wolves. This results in reduced wolf predation on caribou. Most male caribou live about seven to eight years. Females often live longer, to years.

These are very general numbers. Every animal faces its own set of situations that lead to a shorter or longer life. If a caribou lives in a herd that is declining, it probably will have a shorter life than a caribou in a healthy or expanding herd. Also, many caribou die within the first year after they are born, so never reach adult age. Orphan caribou calves are not adopted by other caribou mothers.

If the mother dies, or the calf becomes permanently separated from its mother before the end of its first summer of life, the calf will probably not survive. Several species are known to prey on caribou. Wolves prey on caribou throughout the year, but most frequently in the winter. Bears prey on caribou during spring, summer and fall. Golden eagles take young calves during the early summer, and lynx are able to kill calves in the fall when caribou migrate into forested areas.

When snow is deep, wolverines are sometimes able to kill caribou. Humans have hunted caribou for many thousands of years. The female doesn't actually pick males with large antlers, but the females do often end up breeding with males that have large antlers. This is because the mature males those with the largest antlers work hard to keep younger males with smaller antlers away from the females during breeding time.

The males with the largest antlers are in the best health, and they have been good at finding food all their lives so their bodies can grow these large antlers. When these animals do most of the breeding, their genes are passed on to new generations, and this ensures that the herd remains healthy.

Both caribou and elk are hoofed mammals of the deer family. Caribou males weigh about pounds are generally smaller than elk males weigh about pounds.

Caribou often occur in large herds which migrate over long distances. Elk generally occur in smaller herds, and migrate over relatively short distances. They usually migrate between summer ranges at higher elevations, and winter ranges in mountain valleys. Caribou are native to North America, whereas reindeer are found in Scandinavia and northern Asia.

Some reindeer have been domesticated by humans for hundreds of years. These are used for food and for pulling sleds. Reindeer are smaller and have shorter legs than caribou. A number of reindeer have been imported to Alaska, primarily to the Seward Peninsula.

These herds are owned by Alaska Natives. In the U. There are currently over different wildlife refuges. Refuge lands are legally protected from activities and developments which are harmful to wildlife or their habitat. Human activities which are compatible with refuge purposes are allowed on wildlife refuges.

In Alaska, the Arctic National Wildlife Refuge protects the primary calving grounds and some of the wintering areas of the Porcupine caribou herd, one of the major caribou herds in North America.

Caribou are well equipped to survive in cold, snowy places. In winter, their hair is about three inches long. This winter hair is hollow inside, to trap air and keep warmth near their bodies. This hollow hair also helps the caribou to cross rivers and lakes after spring thaws, because it acts like a life jacket full of air, and helps them to float. Caribou have four hoofed "toes" on each foot. They usually walk on the two larger ones, like a cow does.

When they are in snow, however, these four "toes" spread out wide to act like snow-shoes, which help the caribou walk on deep snow. Caribou are well adapted to cold, dry conditions that were typical in the Arctic region since the last ice age.

When the snow is cold and dry, winter winds will often blow it away, exposing the ground and allowing caribou to walk around and graze more easily. Warmer, wetter winters bring deeper, denser snow and ice that makes it difficult for caribou to dig down to the lichens they eat during winter. Caribou can walk on bumpy ice without slipping, but if they get onto shiny, smooth ice, their hooves slide out from under them and they may fall.

Sometimes they even break their legs this way. Figure 1: Base of caribou foot The caribou Rangifer tarandus is a medium-sized member of the deer family, Cervidae, which includes four other species of deer native to Canada: moose, elk, white-tailed deer, and mule deer.

All are ungulates, or cloven-hoofed cud-chewing animals. However, only in caribou do both males and females carry antlers. Caribou are similar to and belong to the same species as the wild and domesticated reindeer of Eurasia. The caribou is well adapted to its environment. Its short, stocky body conserves heat, its long legs help it move through snow, and its long dense winter coat provides effective insulation, even during periods of low temperature and high wind.

The muzzle and tail are short and well haired. Large, concave hooves splay widely to support the animal in snow or muskeg, and function as efficient scoops when the caribou paws through snow to uncover lichens and other food plants. Caribou are excellent swimmers and their hooves function well as paddles. In winter, the hooves grow to a remarkable length, giving the animal firm footing on crusty snow. In summer, the hooves are worn away by travel over hard ground and rocks. The dewclaws, or small toes, are large, widely spaced, and set back on the foot, greatly increasing the weight-bearing area.

Scent glands located at the base of the ankles are used when the caribou is in danger: the animal rears up on its hind legs and deposits a scent that alerts other caribou to the menace. See Figure 1. In the autumn, the caribou male, or bull, is an imposing animal. It has a rich brown or grey and white coat, a fringe of white hair flowing from throat to chest, and a great rack of amber-coloured antlers. Antler growth starts each year in the spring and is typically complete by late August.

Adult bulls generally shed their antlers in November or December, after they have mated. Adult females, or cows, and young animals carry their antlers much longer, often through the winter. The growing antlers have a fuzzy covering, called velvet, which contains blood vessels carrying nutrients for growth.

See Figure 2. Caribou are usually quiet, but they may give a loud snort. Herds of snorting caribou may sound like pigs.

Especially vocal are the bands of cows and new-born calves, constantly communicating with each other. There are more than 2. Some dwell in forests, some in mountains, some migrate each year between the sparse forests and tundra of the far north, and others remain on the tundra all year.

Barren-ground caribou Photo: Canadian Wildlife Service. The woodland caribou is the largest and darkest of the caribou subspecies.

It is found throughout much of the boreal, or northern, forests from British Columbia and the Yukon Territory to Newfoundland and Labrador. In mountainous areas of western Canada, woodland caribou make seasonal movements from winter range on forested mountainsides to summer range on high, alpine tundra. Farther east, in the more level areas of boreal forest, many woodland caribou occupy mature forest and open bogs and fens, or low-lying wet areas.

Some may move only a few kilometres seasonally, while others may wander extensively. A few herds differ from this pattern, making long seasonal movements between forested and tundra habitats. They are also among the biggest caribou herds in North America, at about and individuals respectively. Peary caribou are small, light-coloured caribou found only in the islands of the Canadian arctic archipelago, where they number about 10 Peary caribou do not normally have significant migrations, although many move among islands, especially if hard icing conditions force them from their normal ranges.

About half of all caribou in Canada are barren-ground caribou. They are somewhat smaller and lighter coloured than woodland caribou. They spend much or all of the year on the tundra from Alaska to Baffin Island. Most, or about 1. About other barren-ground caribou live in smaller herds that spend the entire year on the tundra.

Half of these are confined to Baffin Island. In Canada, caribou are found from the United States—Canada boundary to northern Ellesmere Island, more than 4 km north, and from British Columbia and the Yukon Territory in the west to the island of Newfoundland in the east.

The southern limit of caribou distribution has receded northward since European settlement and this recession continues today.

Ground and tree lichens are the primary winter food of caribou, providing a highly digestible and energy-rich food source. The ability of caribou to use lichens as a primary winter food distinguishes them from all other large mammals and has enabled them to survive on harsh northern rangeland.

Caribou use their excellent sense of smell to locate lichens under the snow, and they dig the lichens out with their wide hooves. In southern coniferous forests they are also able to forage on tree lichens. Although lichens are a good source of energy, they are not a good source of protein nitrogen.

As soon as spring snow melts, caribou are eager to switch to fresh green vegetation, which is rich in nitrogen. Cows that have just given birth are especially in need of protein to replenish their protein reserves and produce high quality milk for their calves. At this time of year caribou focus on sedges and newly unfurling leaves of willow and other shrubs.

Flowers, plentiful on the tundra, also attract a lot of attention. As summer progresses and the quality of the green vegetation declines, caribou once again turn to lichens, to fatten themselves up for the breeding season. Although not always available, mushrooms are highly sought after in August and September. Mushrooms provide a rich nitrogen source late in the summer. Although all caribou move about for different functions over the course of a year, barren-ground caribou make the most dramatic treks.

They are the most efficient walkers of all ungulates in North America, and they are good navigators, unerringly walking hundreds of kilometres from the taiga to their relatively small calving areas on the tundra in spring. They tend to follow frozen lakes and rivers, open snow-free uplands, and eskers, or long narrow hills of soil and rock dumped by glaciers.

Caribou are able to keep a steady direction across frozen lakes so large that the opposite shore cannot be seen. Pregnant barren-ground caribou cows lead the spring migration, followed by juveniles, bulls, and non-pregnant cows, which tend to lag farther and farther behind.

Barren-ground caribou cows head toward traditional calving grounds, where they gather to calve year after year, even from different wintering areas. In contrast, to avoid predation smaller woodland herds generally calve in isolation either in rugged terrain or on islands in small lakes. Caribou cows are usually at least three years old before they can bear young, though 10 to 25 percent of two-year-old cows can also give birth. Cows produce one calf a year, and about 90 percent of adult cows give birth annually.

Most of the calves are born during a day period in May or early June. Calving time tends to be later the further east in North America the caribou are found. The calves are well developed at birth and are able to travel within a few hours.

They start to graze during their first weeks, but until they are about three weeks old, they can digest only milk. The cows and calves soon move to areas where fresh-growing feed is becoming abundant.

During summer barren-ground caribou are often harassed by hordes of mosquitoes, warble flies, caribou nostril flies and, in some areas, black flies. Sometimes the agitated animals will run for many kilometres, stopping to rest only when exhausted or when high winds temporarily disperse the insects. Running from insects places great energy demands on the caribou and may slow their rate of growth by temporarily reducing their search for food.

In large herds, another strategy to reduce harassment of individual animals is to form large gatherings of caribou. These tight groups can number in the tens of thousands. By late September the herds, fat and in good condition, arrive in pre-rutting pre-mating areas.

The rut occurs from mid-September to early November depending on the region. Bulls spar a great deal and sometimes fight for possession of cows. If the calf is too small, the cow will continue to supply milk into the winter, but this reduces her chances of getting pregnant that autumn.

In the deer family, antler size means dominance. By late winter when conditions are most severe, pregnant females are the dominant members of the herd, because they are the only ones to have retained their antlers.

The large bulls lose their antlers after the autumn mating season, and the non-breeders lose theirs soon after that. This is important when conditions are harsh, as the pregnant cows need energy to develop the fetus. Most pregnant females will keep their antlers until after they give birth in June. Little is known of this greyish-coloured subspecies or of the causes of its extinction, but while deterioration of habitat due to climate change may have been a factor, a more important cause was likely overhunting.

Woodland caribou became extirpated from no longer exist in Prince Edward Island before and from New Brunswick and Nova Scotia by the s. Lawrence River. A species is considered endangered when it is facing imminent disappearance from Canada or extinction. The Southern Mountain population of woodland caribou, which occurs in British Columbia and Alberta, has also been assessed and listed as threatened. A threatened species is one that is likely to become endangered if nothing is done to reverse the factors limiting its survival in Canada.

It is also listed under SARA. A species of special concern is one that may become threatened or endangered because of a combination of biological characteristics and identified threats. Numbers have declined by about 72 percent in the last 60 years, mostly because of severe icing episodes due to changing weather conditions, where ice has covered vegetation and led to caribou starvation. These caribou migrate between the mainland and Victoria Island; climate change and increased shipping may make this ice crossing more dangerous.

Caribou are susceptible to and recover slowly from population declines because of their low rate of reproduction. The main factors leading to caribou declines are habitat loss, degradation, and fragmentation, as well as predation. Loss of caribou habitat, which is permanent, occurs when forest is cleared for agriculture, for example.

Habitat degradation means a reduction in the amount or quality of caribou habitat, as happens following such events as wildfires or timber harvesting, or through human disturbance. Habitat fragmentation is the breaking up of habitat areas by roads, timber harvest cut-blocks, pipelines, oil and gas well sites, geophysical exploration lines, and other developments. Caribou in the boreal forest require large tracts of relatively undisturbed, older forest habitat in order to spread out so they are harder for predators and hunters to find, and to avoid the linear corridors that predators and hunters use to gain easier access to their prey.

Older forests tend to be richer than younger forests in the lichens caribou depend on. They are also less favoured by moose and deer, which as prey species of the wolf, attract this primary predator of caribou. Please enable JavaScript to improve your experience. Caribou prefer mostly barren land during the summer months, moving to areas of mixed forests during the colder months.

The caribous range extends from the boreal forests of Newfoundland to British Columbia. This is the largest herd in Canada, numbering at approximately , caribou. Caribou are herbivores.