Caribou Migration Update: February 6, 1997

Robert Mulders

After reading today's caribou data (posted below) and locating the caribou, see if you can answer this Challenge Question:

Challenge Question #1

"What is the temperature today for caribou # 6977?
(And for extra credit: What is the photoperiod?)"

To respond to this question please follow the instructions at the end of this report.

In future updates, we will provide sunrise/sunset data so you can watch how dramatically photoperiod changes in the arctic, and see how this affects the lives of the caribou. (Remember: "Photoperiod" refers to the length of time there is sunlight. You can figure the photoperiod by counting the amount of time between sunrise and sunset.)

Click Here for Caribou Data

For 8 months of the year, caribou habitat is covered with snow. Snow conditions influence where caribou are able to travel, and the availability of their food. With their keen sense of smell, they can find food even when its buried under layers of snow. The caribou's challenge is not only to survive the winter, but to have the energy and strength they will need for the spring migration. Ironically, when the snow finally begins to melt, conditions can be worst of all. Snow that melts on warm spring days can re-freeze when temperatures drop, making it impossible to dig for food.

The caribou's winter diet is predominantly lichens. Lichens grow very, very slowly. Because the growing season is so short, it can take several decades for a lichen to grow a few inches. Then, in one bite, it's gone! This helps explain why caribou need so much room to roam. After all, the food they eat today will not grow back for many years. In the arctic, life is strong and fragile at the same time.

Robert Mulders describes the caribou's winter food:
"There are several hundred species of lichens in this region. Caribou are one of the few animals that can eat this abundant plant because of the acid it contains. Lichens are high in carbohydrates and have the most food value of any plant available to the caribou. Lichens are very, very slow growing. As a rule of thumb, it can take 50-100 years for lichens to grow back. The growing season in the arctic is short--in some places as few as 40 days a year--and lichens grow only around 1/16 of an inch per year. So if an area is overgrazed or burned the caribou won't be able to use that habitat for many years. In fact, there have been fires in northern Manitoba within this herd's winter range and we're concerned how this might affect their use of the area.

"In the wintertime, caribou obtain the lichens by 'cratering' through the snow. When we go out for field studies in late March we've seen instances where they've cratered through snow as much as 2 feet deep. In most winters they can forage without difficulty but some years starving can occur if an icy cover forms and prevents them from obtaining food easily."

Many lichens are very sensitive to pollution in the air. When there are too many harmful things in the air, lichens die. This is why they are sometimes called "indicator" species. They can tell us if the air is clear and clean. Even in the remote arctic, pollution has contaminated lichens. Pollutants have drifted through the atmosphere, appeared in the lichens, then in the flesh of the caribou--and then in the humans who eat the caribou. Through studies of arctic women who are nursing their babies, these contaminants are known to even reach babies when they drink their mother's milk.

How to Respond to Challenge Question #1:

1. Address an E-mail message to: jn-challenge-caribou@learner.org

2. In the Subject Line of your message write: Challenge Question #1

3.In the body of the message, answer this question:

"What is the temperature today for caribou # 6977? (And for extra credit: What is the photoperiod?)"

Try this!
Write a vacation postcard from a manatee to a caribou. Using today's weather information, compare and contrast the places these two creatures inhabit. Be as descriptive as you can. What does each animal experience in the course of a day? In what ways are your habitats different? Are there any ways in which they're the same?

The Next Caribou Migration Update Will be Posted on February 20, 1997.