Why do caribou migrate

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.

Caribou used to live in Maine and the northern Great Lakes states, but they are no longer found in those areas. A small, endangered woodland caribou herd exists along the Canadian border with northern Idaho and northwest Montana. An unusual situation exists at South Georgia, an island near Antarctica, where reindeer from Norway were introduced in the early 's. Because of the opposite seasons in the southern hemisphere, these animals had to change the timing of breeding and calving by a half year.

The woodland caribou in that region live in old growth forests. They do not migrate very far between their summer and winter ranges less than 40 miles, in some cases , but they are very sensitive to human disturbance and to forest loss.

Woodland caribou do poorly when forests are fragmented into small areas by roads or by logging operations. As human activities increase, woodland caribou, and other animals sensitive to disturbance, have disappeared. Only a few areas in the United States still support woodland caribou, and the animals are endangered in these areas. There are currently four very large herds of caribou and wild reindeer: the Porcupine Herd, the Western Arctic herd in northwest Alaska, the Qamanirjuag Herd in Nunavut, Canada, and the Taimyr Peninsula herd in northern Siberia.

Each herd is currently estimated at over , individuals. Due to different census techniques and schedules, as well as annual fluctuations in populations, it is not possible to say for certain which of these three herds is currently the largest.

Several caribou herds in northern and northeastern Canada that used to be quite large have recently declined to very low numbers, causing concern about the future of these herds. Adult caribou range in size from 3 to 4 feet tall. Their size and weight varies by sex and region. For example, caribou are fairly small in northern Alaska.

Males average about to pounds, females about pounds. In southern Alaska, caribou are considerably larger -- males average to pounds and females average to pounds. Caribou are the only deer in which both sexes have antlers. Males shed their antlers in late fall, just after the breeding season young males retain their antlers longer that mature males.

Pregnant females keep their antlers all winter and shed them soon after the calves are born in the spring. Non-pregnant females shed their antlers during the winter. Caribou do not store much of their fat in muscle tissue, so their meat is leaner than beef which often is "marbled" with fat. Caribou meat is considered more healthy than beef, and is quite tasty. Caribou commonly gather in large herds about three weeks after the calves are born. At this time the great herds increase their rate of movement, and caribou tend to be less wary when they are in very large groups.

Caribou will generally not let you approach them, but if you sit quietly in the path of a group that is moving in your direction, you might be fortunate enough to see them up close as they pass by. Caribou populations are rarely stable for very long. Under natural conditions, the size of a particular herd will tend to increase slowly for years, then decline, sometimes rapidly, before again beginning to increase.

Many things can influence whether a herd is increasing or declining. 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.

Caribou are native to North America, whereas reindeer are native to northern Europe and Asia. Alaska does have some reindeer, however, imported from Siberia in the late 19th and early 20th centuries.

Some people use the term "reindeer" to refer to domesticated work animals, such as those pulling Santa's sleigh, but there are both wild and domestic herds of reindeer. Caribou, on the other hand, are wild-living and long-migrating.

Indigenous groups, including the Sami in northern Scandinavia and the Nenet in Russia's Arctic , herd reindeer and use them for their meat. That's also likely why reindeer evolved to be stockier than caribou.

Caribou make one of the world's great large-animal migrations. As summer approaches, they head north along well-trod annual routes. Some herds may travel more than miles to get to their summer grazing grounds.

They'll spend the summer months feeding on the abundant grasses and plants of the tundra. An adult caribou can eat 12 pounds of food each day. This is also when they give birth. When the first snows fall each year, the caribou turn back south. Herds of female caribou, called cows, leave several weeks before the males, which follow with yearling calves from the previous birthing season.

The herds spend the winter in more sheltered climes and survive by feeding on lichens. Caribou are taller and lankier than reindeer, likely because they evolved to make these long migrations.

Caribou, as part of the deer family, have large hooves that are useful tools for life in the harsh northlands. They are big enough to support the animal's bulk on snow and to paddle it efficiently through the water. The hoof's underside is hollowed out like a scoop and used for digging through the snow in search of food. Its sharp edges give the animal good purchase on rocks or ice. Caribou are the only deer in which male and females both have antlers—though only some females have them.

Cows have one calf each year, which can stand after only a few minutes and move on with its mother by the next day. The fall migration starts at a more leisurely pace that will be dictated by the weather as the animals progress. They speed up if triggered by a sudden temperature drop or substantial snowfall, but if it warms up, migrating caribou will slow their pace or even reverse course.

Along the way, bulls become increasingly aggressive and sparring becomes more frequent, culminating in a brief breeding period before the herd arrives at its winter range. Winter is the only season of the year when caribou herds remain stationary. Jennifer Mueller began writing and editing professionally in , when she became sports editor of her university's newspaper while also writing a bi-monthly general interest column for an independent tourist publication. By using the site, you agree to the uses of cookies and other technology as outlined in our Policy, and to our Terms of Use.

History The ancient caribou once shared grazing grounds with prehistoric mammals such as mastodons and woolly mammoths. Spring Migration The spring melt of arctic snow triggers pregnant females to begin the annual caribou migration to calving grounds, where the herd will pause briefly while calves are born.

Summer Scatter As spring turns to summer, mosquitos and flies proliferate in caribou calving grounds, which are frequently close to the Arctic Ocean or other large bodies of water. Fall Migration As temperatures decrease in the fall, caribou herds gather and slowly head southward.