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   Porcupine Caribou Herd


Porcupine Caribou Herd

 


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THE PORCUPINE CARIBOU HERD

 

Caribou are large, wild, elk-like animals, which can be found above the tree-line in arctic North America and Greenland. The earliest caribou are believed to date back 1.5 million year!


Caribou are truly what we call “chionophiles,” a word that means snow-loving animals!


Living on lichen in the wintertime, they are very well adapted for the harsh Arctic tundra with their compact bodies, short tail, small ears and double layered coat. Caribou migrate great distances every year – to feed and give birth (calve). Large and wide (concave) hooves make works like snowshoes, making it easy for them to move on snow or muskeg. In the wintertime they grow a longer nails with sharp edges, which they use to dig through the snow to uncover their food, the lichen.


Caribou are the only members of the deer family whose females as well as the males (bulls) grow antlers. Bull antlers can reach 4 feet in width! A Caribou calf can run within 90 minutes of its birth! Caribou have unique hairs which trap air providing them with excellent insulation. These hairs also help keep them buoyant in the water. They are very strong swimmers and can move across wide rushing rivers and even the frozen ice of the Arctic Ocean!


The Arctic National Wildlife Refuge is home to some of the most diverse and spectacular wildlife in the Arctic. The Refuge's rich pageant of wildlife includes 36 fish species, 36 land mammals, nine marine mammals, and more than 160 migratory and resident bird species.

The Arctic National Wildlife Refuge is also home to the 129,000 member Porcupine caribou herd.

Named for the major river within its range, the Porcupine herd uses an area the size of Wyoming in the Refuge, Yukon, and Northwest Territories. The herd winters in the southern portion of its range, including the Refuge, where they are an important resource for the native Gwiich’n people, supplying them with 80 % of their resources!

Twice a year the herd migrates more than 700 miles to and from its traditional calving grounds on the arctic coastal plain. Sometime in April, the caribou head north. The route they take depends on snow and weather conditions. By early June, the pregnant females reach the calving areas and give birth. Shortly thereafter, most, and often all, of the herd joins the cows and calves on the coastal plain of the Refuge. In late June and early July, when hordes of mosquitoes hatch, the caribou gather in huge groups numbering in the tens of thousands. Seeking relief from the insects, they move along the coast, onto ice fields, and to uplands in the Brooks Range. The herd leaves the coastal plain by mid-July, heading back east and south toward its fall and wintering areas. Just as no one knows in advance precisely where most of the caribou will drop their calves in the spring, no one knows until it happens whether the majority of the herd will winter on the south side of the Refuge or in Canada.

Hunted by local residents, chased by predators, harassed by insects, challenged by river crossings, and faced with difficult terrain and weather, the Porcupine herd confronts many hardships. Yet it thrives, every summer staging a magnificent wildlife spectacle on the Arctic coastal plain. 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 National Wildlife Refuge.

This section of PolarHusky.com will continue to grow…So, make sure to check back often!

In the mean time here are answers to some common caribou questions!

Porcupine Caribou Questions

Why do caribou migrate?

Some animals stay in one area their entire life. Others, like caribou, migrate on long journeys. Caribou migrate between summer and winter ranges. Their summer range provides nutritious food that helps the new calves and the other caribou grow healthy and fat before winter. But the summer range is a harsh and windy place during winter, so the caribou move to a winter range where conditions (weather, food, snow cover) are more agreeable.

What happens to the young when caribou migrate?

Soon after birth, the caribou calf and its mother develop a strong bond. They try to stay close to each other, and they can recognize each other by smell and by the sounds they make. This is important because the caribou calves are fast runners within hours of their birth. When caribou migrate, the calves run with their mothers. If they become separated, the mother searches for many hours to find her calf.

How far do caribou migrate?

Caribou herds migrate different distances. Large herds are more apt to migrate long distances, while smaller herds often migrate shorter distances. For example, the Porcupine caribou herd, which contains about 129,000 animals, migrates between summer and winter ranges that are about 400 miles apart. The Central Arctic herd, which contains about 20,000 animals, migrates between summer and winter ranges that are about 120 miles apart. Biologists have discovered, by using satellites to track caribou, that the herds actually travel much farther than the straight-line distance would indicate. They move to and fro over a wide area, adding many miles to their journeys.

Will caribou cross barriers when they migrate?

It is quite common to find situations where caribou are reluctant to cross roads, berms 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). Researchers have learned there are many factors (traffic levels, time of year, degree of visual obstruction, etc.) which can influence caribou reactions to roads and thus their chances of crossing successfully. 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 build 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.

Do caribou migrate for weather or food?

Certain weather conditions, such as the first severe storm in the fall, stimulate caribou to migrate toward their winter ranges. After the calves are born in the spring, all the caribou in the herd come together on the summer range. 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. When these large herds form, their rate of movement naturally increases.

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, they will run from a predator who gets too close to them (actually, they will run from anything that "spooks" them.)

There are two characteristics of caribou that may make them appear to show less than the proper amount of fear toward a predator:

1) Caribou may come up and investigate something they aren't sure about. Such as a dog team or the sleds while our team members are sitting next to it eating lunch! As soon as they figure out, what is going on they are gone. You can also lure them in by acting strangely. A ploy is to lie on the ground on your back, slowly waving one of your legs in the air. Again, they'll come quite close to see what's what, before running away.

2) Caribou do not want to spend any more energy than they have to. 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 quite 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 is not about to catch them (or after they figure out that you're a person sitting). 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.

Where are Caribou found?

Caribou and reindeer are the same species (Rangifer tarandus). Reindeer are a domesticated variety of caribou that are herded by humans and used for pulling sleds. Most reindeer occur in Scandinavia and Siberia. They generally are smaller and have shorter legs than their wild relatives. In Siberia, caribou are referred to as "wild" reindeer.

Caribou are found in Alaska and Canada. Caribou used to live in Maine and the northern Great Lakes states, but they are now extinct in those areas. A small, endangered caribou herd exists in 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 1900'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. (A population of 8 reindeer are believed to live at the North Pole. These unusual animals, guided by one with a red nose, are reported to have the capability of flight!)

What is the largest herd of caribou?

There are currently three very large herds of caribou, the Western Arctic herd in northwest Alaska, the George River herd in northern Quebec, and the Taimyr Peninsula herd in Siberia. Each herd is currently estimated at 500,000 or more individuals. Due to different census techniques and schedules, as well as annual fluctuations in populations, it is not possible to say which of these three herds is currently the largest.

What is the size of caribou?

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 275 to 375 pounds, females about 200 pounds. In southern Alaska, caribou are considerably larger -- males average 400 to 600 pounds and females average 200 to 300 pounds.

How long do caribou keep their antlers?

Caribou are the only deer in which both sexes have antlers. Males shed their antlers following the fall breeding season (young males retain their antlers longer that mature males). Pregnant females shed their antlers soon after the calves are born in the spring. Non-pregnant females shed their antlers during the winter.

How does caribou meat compare with beef?

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.

Will caribou trample humans?

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. If you sit on the tundra in the path of the herd, and make no rapid movements to frighten the animals, they will walk around you at quite close range.

What keeps caribou populations in equilibrium?

When factors having negative effects on caribou productivity and survival occur more frequently (more bad years than good years), populations decline. Caribou populations increase when the opposite occurs. If positive and negative effects are balanced, caribou populations remain stable.

Usually a combination of factors causes 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 often 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.

How long do caribou live?

Male caribou live about seven to eight years. Females live slightly longer, to 10 or more 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 (getting smaller over the years), 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, and never reach adult age.

What are caribous' natural predators?

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.

Do female caribou pick males with large antlers to breed with?

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.

What do Wildlife Refuges protect caribou from?

In the U.S., the National Wildlife Refuge System preserves a national network of lands and waters for the conservation and management of fish, wildlife and plants for the benefit of present and future generations. There are currently over 500 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.

Do mosquitoes play a role in caribou behavior?

Mosquitoes do play an important role in caribou behavior. Mosquitoes appear in early summer, just as the caribou are shedding their long winter hair. The insects can easily draw blood from the caribou at this time, and seriously torment the animals. The problem is worst when the weather is warm, winds are calm, and the caribou are in damp tundra areas where the mosquitoes breed. Caribou try to avoid mosquitoes by a variety of strategies, depending on where they live: they run; move to higher areas that may be windy and dry; move to snow or ice patches that are too cool for the insects to be active; move out into large lakes or shallow salt water; and/or bunch up into very dense groups.

The running, blood loss, and inability to spend time eating causes caribou to lose weight during a time of year when they need to be getting fat for the coming winter. Mosquitoes are therefore a major influence in the lives of caribou.

Are calving grounds essential for caribou survival?

Yes. Each spring, pregnant female caribou begin long migrations towards their traditional calving grounds. Their instinct to reach these areas is very strong, and enables them to travel through deep snow and storms, and to cross rivers flooding with icebergs to reach the calving grounds at just the right time. Soon after they arrive on the calving grounds, the calves are born. Studies have shown that predators are less abundant on the calving grounds, so the young calves are safer at a time when they are too weak to escape from wolves and bears. The calving grounds also have an abundance of highly nutritious new plant growth which enables the mother caribou to produce rich milk for their calves. This is very important as it allows the calves to grow rapidly so that they can escape from predators and harassing insects, and keep up with the herd as it migrates to the winter range. In summary, it is the special conditions of the calving grounds which improve the survival of calves and ultimately the entire herd.

Source: U.S. Fish & Wildlife Service. 2004.