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.
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Lichen-Winter
caribou food Photo courtesy USGS |
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| 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:
There is
a Reading Writing Connection
for this selection.
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