Caribou (Rangifer tarandus) belong to the deer family and have sustained the indigenous peoples of the North for 20,000 years. They are the most numerous large mammals in the Arctic National Wildlife Refuge, an area comparable to the size of Wisconsin, located in the northeast corner of Alaska. In this area of North America lives the Porcupine caribou herd.
The Porcupine Herd, Though Large, is Dwindling
There are more than 50 caribou herds worldwide, and of the 34 herds that scientists monitor in North America, the Porcupine herd—named after the Porcupine River, which runs through part of its migratory route—is among the ten largest on the continent.
In recent years the herd was reported to consist of over 150,000 animals, but has recently diminished to about 100,000, according to an October 8, 2009, article for the Christian Science Monitor entitled “Mighty caribou herds dwindle, warming blamed,” by Charles J. Hanley.
The herd uses more than one route in its overall movement to reach the North Slope, the northernmost plain between the tree line and the sea, where the caribou and their new calves will subsist on grasses, mosses and lichen in the summer months. To get there, pregnant females, yearlings and other cows depart first each May, traveling separately from the male caribou.
An excellent swimmer with broad, paddle-like hooves, a caribou is able to cross rivers such as the Porcupine, Chandler and Coleen, that are along the routes northward. The caribou’s hollow winter hair enables the animal to float more easily because of the air trapped inside, as well as keep it warm.
Caribou Endure Pests During Their Summer Rest
After the herd comes together in the summer range, and cows have delivered their calves by mid-June, the herd must endure pesty insects while foraging during the remainder of June into July. Since the caribou is also shedding its winter coat at this time, its skin is quite vulnerable to the swarming mosquitoes.
A caribou can lose up to a quart of blood in a week from mosquitoes, so the animals congregate together to reduce the number of insects that can access each animal. The caribou will also move closer to the shore, where cool wind off the water keeps mosquitoes away. Other means of escape include going into the water or moving to snowy areas too cold for the insects to survive.
As the mosquitoes decline and the caribou start moving toward the foothills and mountains, they then deal with warble flies and nose-bot flies, which torment the caribou in July in August, causing the animals to shake their heads, stomp and race around from the discomfort of these insects’ larvae in their bodies.
The time that a caribou spends in distress from insects like mosquitoes takes away from the precious hours available to rest and feed to prepare for winter. The plants in the arctic plain help make a nursing caribou’s milk the most nutritious of all land mammals, which helps its calf grow fast and strong in the short time it has before the migrating herd starts moving back to winter grounds.
Caribou Use a Strategy to Protect the Winter Food Supply
The Porcupine herd will sense when it is time to start migrating southward in the fall, toward its winter range. Often this will coincide with the first big storm of the season. The herd will not always travel the same distance every year, using a strategy to make the best use of the land.
By varying movements within its winter range from year to year, the herd protects the plants it eats from decimation. Not only does the herd change where it feeds, it also keeps moving within its feeding range so that any one area is not overeaten.
For eight winter months, the Porcupine caribou herd spends its time pawing through the snowy lands south of Alaska’s Brooks Range and in the Yukon Territory of Canada to find lichen to eat. It is this behavior that led to the animal’s name. The word caribou is derived from the Micmac Indian word galipu, which means “snow shoveler.”
Board Helps Manage Porcupine Herd
Because caribou are culturally important to the Gwich’in, a First Nation/Native Alaskan people who live in the Porcupine herd’s range, and because the herd’s migration takes it across the U.S. border into Canadian territory, a board was formed to ensure the herd’s protection.
In 1987 an international agreement mandated the formation of the Porcupine Caribou Management Board, which makes guidelines surrounding issues related to land development, hunting, predators, climate change and more.
Developing plans about the herd’s population, health and habitat requires careful management when the board has to take into consideration respect for the needs of the natives, who depend on caribou to live, and compromises with those who want progress in the oil-rich arctic areas.
Note: Specific migratory route information is available on the UConn Arctic Circle web site (use the site's search function to find the "Caribou in the Arctic Refuge" page). A migration map is also available at www.mapcruzin.com/arctic_refuge/images/move87.jpg.
Sources:
- “About the herd.” Porcupine Caribou Management Board (web page). 25 January 2010.
- “Caribou in the Arctic Refuge.” Arctic Circle. 25 January 2010.
- “Caribou Migration.” Arctic National Wildlife Refuge (web page). 26 January 2010.
- Hanley, Charles J. “Mighty caribou herds dwindle, warming blamed.” The Christian Science Monitor, 08 October 20009.
- Miller, Debbie S. A Caribou Journey. New York: Little, Brown and Company, 1994.
Cheryl Kraynak - Cheryl Kraynak has worked in publications and communications for 20 years and has expertise in the natural world and creative arts.
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