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These cookies do not store any personal information. Non-necessary Non-necessary. For example, the Porcupine caribou herd, which contains about , animals, migrates between summer and winter ranges that are about miles apart.
The Central Arctic herd, which contains about 30, animals, migrates between summer and winter ranges that are about miles apart.
Biologists have discovered, by using satellites to track caribou, that the herds actually travel much farther than the straight-line distance between summer and winter ranges would indicate. They move to and fro over a wide area, adding many miles to their journeys. Porcupine Caribou herd animals, for example, have been observed to travel over miles per year.
It is quite common to find situations where caribou are reluctant to cross roads, berms, pipelines and other related obstacles.
Being terrestrial migrators, caribou must deal with what ever is placed on the land by human development birds are able to fly over most human structures and continue their migratory habits. Caribou need to move freely over vast areas to forage, avoid predators, escape from harassing insects, and reach favorable summer and winter ranges.
Structures such as highways may deflect caribou movements, and reduce their chances for survival. A single road within a caribou herd's range usually is not as serious as a system of many roads.
In some instances, roads and pipelines can be constructed in ways that reduce problems for caribou. For example, a ramp may be built to direct caribou over a road, and a pipeline may have buried sections for caribou to pass over.
These modifications can help, but do not always work. Pank, K. Whitten, and W. Seasonal movements of caribou in arctic Alaska as determined by satellite. Canadian Journal of Zoology The effect that oil development may have on caribou migrations depends on many things, such as the location of the development in relation to critical habitats and migration paths, the density and design of the buildings, pipes, and roads, as well as the time of year that caribou are in the development area.
For example, caribou are most sensitive at calving time, and studies have shown that caribou may be displaced from their traditional calving grounds when oil development occurs there. Other factors, such as weather, may also influence how much development may affect caribou. Caribou may be able to tolerate higher levels of disturbance when the weather is good and caribou are in good shape, but they may be more vulnerable to disturbance when they are also stressed by bad weather or a scarce food supply.
Based on several years' observation of satellite-collared animals of the Porcupine Caribou herd, caribou do not migrate the same distance each year. This is because they often use different portions of their winter range from year to year. By using this strategy, caribou are able to eat winter food over a wide area, which reduces the possibility of eating up all the available food in any one area.
Although parts of the migration routes are used almost every year, there are variations in the specific routes that are taken, depending on weather, snow conditions, and where caribou spent the winter.
As a result, caribou migrate different distances each year. Migration probably helps caribou access the best type of food available during each season, and also helps the herd avoid predation because predators are generally less mobile, and thus only have access to the caribou for part of each year. Some weather conditions, such as the first severe storm in the fall, seem to stimulate caribou to begin migrating toward their winter ranges and spring migration is probably stimulated by the pregnant cows feeling the instinct to go to their preferred calving grounds.
For large herds such as the Porcupine Caribou herd in the Arctic National Wildlife Refuge, the caribou must keep moving so they don't eat all the available food. We can't tell you how many die while crossing rivers, although this undoubtedly does happen. We do know, however, that caribou have been encountering rivers for many thousands of years, and yet the herds survive. Caribou have many strategies that help them cross rivers. They including the calves are excellent swimmers, and their hollow winter hair helps them float high in the water.
Caribou do not always plunge blindly into rivers: sometimes they scout out safer crossing areas or wait for better crossing conditions.
We've observed migrating pregnant females decide not to cross a raging river, but instead, give birth before crossing. To biologists, a population is a group of animals that commonly interbreed among themselves, but do not interbreed with animals from neighboring populations.
In the case of caribou, breeding between neighboring herds does occur, but is usually much less common than breeding between caribou within a herd. Each herd maintains a unique calving range, separated from those of other herds. Most caribou herds are named after the area where they are found, or a prominent geographic feature of their range.
Do caribou stand around and let wolves eat them? It sometimes may look like caribou are ignoring predators such as wolves or bears. Unless they are incapacitated, however, caribou will run from a predator who gets too close to them.
There are three characteristics of caribou that may make them appear to show less than the expected amount of fear toward a predator:. They know what's a safe distance from a predator, and they can tell by watching how a wolf or bear is behaving whether the predator is a threat. So it is very possible to see a bear or wolf pass through a herd of caribou.
While the predator ambles along, the caribou do not run away, but continue to feed or walk. When the predator begins running toward a group or an individual animal, then those caribou run away. When caribou are not alarmed, they walk slowly, extending the head forward and downward. When alarmed, caribou perform a special behavior to warn other caribou of danger. They'll do this if a predator gets too close, but isn't about to catch them or after they figure out that you're a person sitting on a rock.
An alarmed caribou will trot with the head held high and parallel to the ground, and the short, normally floppy tail held up in the air. They gallop very quickly when being chased closely by a predator.
Caribou and reindeer are the same species Rangifer tarandus. Caribou are native to North America, while reindeer are found in Scandinavia and northern Asia, where some have been domesticated. Domestic reindeer are herded by humans and used for food and for pulling sleds. They generally are smaller and have shorter legs than caribou. Caribou are found throughout Alaska and northern Canada, and along the west coast of Greenland. Unlike many other members of the deer family, bull caribou do not control a harem of cows.
Instead, they control a space around themselves, and prevent other bulls from breeding females within their space. The largest bulls shed their antlers in late October, but small bulls and non-pregnant cows do not shed their antlers until April. Pregnant females usually retain their antlers until calves are born in late May or early June. In Alaska, caribou prefer treeless tundra and mountains during all seasons, but many herds winter in the boreal forest taiga. Calving areas are usually located in mountains or on open, coastal tundra.
Caribou tend to calve in the same general areas year after year, but migration routes used for many years may suddenly be abandoned in favor of movements to new areas with more food. Changing movements can create problems for the Native people in Alaska and Canada who depend upon caribou for food. Caribou movements are probably triggered by changing weather conditions, such as the onset of cold weather or snowstorms. Once they decide to migrate, caribou can travel up to 50 miles a day.
Caribou apparently have a built in compass, like migratory birds, and can travel through areas that are unfamiliar to them to reach their calving grounds. To see herd ranges in greater detail, see the map of the 32 caribou herds in Alaska. These animated maps show the movement of caribou herds over the course of a year. The Porcupine herd ranges into western Canada. Note that the caribou bunch up or aggregate in June on the calving grounds.
Caribou herds are counted shortly after these aggregations begin to occur, typically in early July. Data were collected from about — The Network is an international group of scientists, managers and community people who have a common interest in caribou. There are approximately , wild caribou in Alaska including some herds that are shared by Alaska and Canada's Yukon Territory. Caribou are somewhat cyclic in number, and the timing of declines and increases, and the size to which herds grow is not very predictable.
Although overhunting caused some herds to remain low in the past, today, varying weather patterns climate , population density, predation by wolves and grizzly bears, and disease outbreaks determine whether most herds increase or decrease. Willow is a favorite summer food type for caribou as it is highly digestible and packed with beneficial nutrients and proteins.
Female caribou are unique in that they are the only members of the deer family to grow antlers bonus question: why? As we can see in this video, another female companion shows off her beautiful velvet antlers while eating willow. Bear flower Boykinia richardsonii is a favorite of bears, but also of caribou! This video shows an adult female caribou, in addition others in the herd, foraging on a beautiful patch of bear flower leaves.
You can see the flowers have already bloomed and dropped, but the leaves are still a favorite food when it is available.
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