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Barren-ground
Caribou
Annual Cycle
The
major barren-ground caribou herds in the Northwest Territories spend the
winter in forested areas below the treeline.
The exceptions are the Ahiak herd and Cape Bathurst herd which
spend much of the winter on the tundra.
In March and April, barren-ground caribou begin to move in a great
northward  migration. Individuals
band together, each small group joining another, until long lines of
caribou are moving steadily to their calving grounds, which may be as far
as 700 km away. By the time
the herds pass the last stunted trees of the northern forests and spread
out over the still frozen barren-lands, they may number in the thousands. Pregnant cows lead the way and their urgency to reach the
traditional calving ground is so great that nothing can hold them back.
Even if calves are born along the way, they may be left behind as
the cows continue on with the herd.
Bulls
and immature caribou lag behind the cows and do not go all the way to the
calving grounds. They leisurely graze their way northward following the
retreating snow line, eating the nutritious new leaves sprouting on the
sedges and willows, and waiting for the cows to return with the new
calves. Many do not leave the forest until early June.
Calving
grounds are often located in high, rocky areas, where there is little
shelter from wind and driving snow. These conditions are favourable as
they provide patches of bare ground that allow the cows to feed. If the
spring snow melt is late and plants have not yet begun to grow, cows can
continue to feed on lichens on the rocky slopes. If spring arrives early
or on time, cows can feed on cotton-grass flower buds and green sedge
leaves.
 Most
calves are born within a few days of each other during the first two weeks
of June and temperatures are usually near the freezing point. Calves can
stand and suckle within a few minutes of birth. In an hour, a calf can
follow its mother, and within a few days it can outrun a man. Maturing
quickly helps newborn calves survive against predation from wolves and
grizzly bears that are in the calving grounds. Most wolves remain within
the treeline to den and are a reduced threat to cows and newborns at this
time. As well, the high, rocky areas of the calving grounds are beyond the
reach of most wolves that may pursue the hunt. These rocky slopes however,
are home to grizzly bears that are quick to prey on newborn calves.
As soon as calving is over, cows and calves slowly begin
their long trek back toward the winter range.
As spring
 turns into summer, the cows meet up with the bulls that
have continued to drift north. In an attempt to reduce the intense
disturbance caused by mosquitoes,
warble flies and
nose-bot
flies, caribou form dense groups or "post-calving
aggregations" that can number in the tens of thousands.
They try to hide their faces, snort, stamp their legs, crowd
together or gallop away to avoid the flies.
Cooler temperatures and windy conditions can keep the flies
grounded and provide some relief for the caribou. Because caribou are
unable to feed when they are tightly packed together and they are shedding
their winter coats, they look thin and ragged as they cross the summer
tundra.
In
August and September, insect disturbance decreases allowing caribou to
focus on feeding. They break
into smaller bands and slowly move across the tundra toward the treeline.
They rapidly gain weight as they feed on mushrooms, lichens, shrubs
and grasses. The cows,
in particular, have to gain enough weight to be able to breed in the fall.
The rut occurs in October and is spectacular in its intensity.
The bulls are in their prime with glossy new
coats. Their antlers are polished and smooth from being scraped against
shrubs and small trees.
Their
flowing white manes swing back and forth as they threaten and challenge
each other.
The rut may last for two or
three weeks, however most cows bred within a few days of each other. By
the time the rut is finished, winter has settled on the north.
The
distribution of barren-ground caribou changes constantly during the winter
as they search for places where the food is abundant and the snow is the
shallowest. Caribou use their
excellent sense of smell to lead them to lichens under the snow and their
broad hooves are designed for digging feeding craters through snow and
ice. Lichens are the mainstay
of their winter diet, but sedges, and evergreen leaves are also eaten.
When spring arrives the caribou once again begin their migration to
the calving grounds.
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