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Winters’s Dining Selection: Lichens

Caribou are herbivores, or plant-eating animals. You might think this poses a problem in the winter months. Most Porcupine caribou spend the winter below treeline, in the forested Richardson and Ogilvie Mountains. November to March, they move slowly through their wintering range in these boreal forests.

Lichen-Winter caribou food
Photo courtesy USGS

Snow craters where caribou dig for lichens.

Likin' Lichens
Caribou eat different kinds of plants throughout the year, but they have one main menu during the cold winter months. Lichens. For simplicity we will call lichens a kind of plant, but they are really more complicated than that. Lichens are a combination of a plant (algae) and a fungi growing together in a symbiotic relationship. Lichens look different from most plants. They come in many colors. They have many different shapes, too. They can grow on trees, rocks, rotting wood and the forest floor. Within the the Porcupine caribou range the lichens are mostly found growing on the ground under the snow in winter.

Tough but Nutritious
Caribou are some of the few animals that can eat this abundant plant. Daily they eat an average of about 3 kilograms of lichens. This is the equivalent of eating 2 garbage bags full of lichens a day.Compared to most plants lichens are very tough and contain acid which might keep other animals away. Also high in carbohydrates lichens have the most food value of any plant available to the caribou. Fortunately the caribou have an efficient digestive system that can utilize all the nutrients available in lichens.Learn more about the caribou's digestive system and their unique four-chambered stomach.

Lichens are very, very slow growing. In general, it can take 50-100 years for lichens to grow back once they have been eaten. 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.

Finding the Tasty Lichens
Porcupine caribou have a very keen sense of smell. In the wintertime, they can smell the lichens through the snow. They find them by 'cratering' through the snow. Even temperatures as low as minus 50 degrees Celsius have little effect on this activity. Hungry caribou will crater through as much as 2 feet of snow to get at the lichens. 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.

Lichens as Indicator Plants
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. Remember that lichens can live for a very long time- long enough for pollutants to accumulate in them. 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.
Read more about contaminants and research that has been done with this important food supply:

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