mother polar bear and cub on tundra mother polar bear
For my entire life, I’ve wanted
to see polar bears in the wild. Our trip
to Churchill, postponed last year because of Covid, finally happened, and was
all I could have wished for. Over 3 days
in this remote area of northern Canada, we enjoyed 19 polar bear sightings,
with 17 different bears. What a thrill!
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| mother with her 2 cubs |
Polar bears live on pack ice during the winter, hunting their primary food, seals, through breathing holes the seals scratch through the layer of ice. Because the seals know the habits of the bears and the bears know those of the seals, this is a deadly cat and mouse game, with the seal becoming bear food if it isn’t alert and the bear starving if it can’t catch seals.
Seals must come up for air, so they use their claws to pull off chunks of ice to create a hole wide enough for their bodies to poke up for a breath of air. The ice is a good conductor of sound, which the polar bear knows, so the bear has to be very patient and quiet in order to snag the seal coming up for air. It will sit for hours without moving, watching the air hole, hoping for a seal to pop up. Since seals can swim much faster than bears, surprise provides the only opportunity for the polar bear to be quicker than the seal.
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| male bear by the willows |
Polar bears look a bit like giant
white torpedoes, with smallish heads compared to their huge bodies, billowing
into very large hind quarters. This must
help them when they dive into the air hole after a seal because their heavy
butts on the ice help them stay on the ice as they pull the struggling seal out
of its air hole. When a seal pops up
through the hole, the bear pounces, splashing its head with jaws wide open into
the hole to grab the seal. Then it pulls
the seal back onto the ice to have its meal.
Polar bears feast while they’re
out on the ice. They can put on 60% of
their body weight during the winter months of seal hunting, much needed during
their 6 or 7 months of fasting when the ice melts and they must survive on
land, using up their winter fat. A large
seal will last a polar bear 6 to 7 days.
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| young bear sniffing at our tundra buggy |
Polar bears don’t hibernate, but a pregnant female will scoop out a den under the snow, often with a separate chamber for her cubs, where she gives birth. The den will have an air hole for each chamber, quite an ingenious design. She will stay in her den with her cubs until they are 8 weeks old and can go out onto the ice with her. Usually, she will stay with her cubs for 18 months to 2 years, teaching them to hunt seals and survive the lean times. When her cubs start to wander off to check out their surroundings, she will begin to search for a male to breed again.
We watched a female polar bear and her cub lolling on the tundra, enjoying a rest. Suddenly, their noses pointed straight up and they leaped off the ground and took off running, not something they usually do. Soon, we saw a large male bear following their scent. He was a threat to the cub, so the mother and baby did not stop until they were far off on the opposite shore of the bay.
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| curious cub |
Male polar bears will kill a cub
in order to get the female to produce eggs again. Polar bears are cannibals, so a male that
kills a cub will probably eat it, another addition to its diet. Females don’t produce eggs on a regular
cycle, but will ovulate when they begin to mate. The eggs will only attach to her uterus if
she is fat enough to survive and incubate the embryos. Given the polar bears’ shorter time on the
pack ice for hunting now, the inability to become pregnant due to insufficient
body fat is another big threat to polar bears.
Our guide told us that most sows are producing 1 or 2 cubs today while a
few decades ago, they routinely produced 3.
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| mother bear and tundra buggies |
When the pack ice begins to break up, the bears may be a hundred miles from land. They must swim to land, sometimes scrambling up on an ice floe, then heading back into the water. The longest recorded swim was a female who swam 9 days to reach land. Bears do drown if they become too exhausted while swimming to land, so it is always a judgment call on the part of the bear as to when to give up hunting and head for land, and the inevitable summer without food. Mothers must escort their cubs during these swims, so may start for land earlier to reduce the swimming distance for their cubs. But, the consequences of leaving the ice before they have eaten enough to last them for the summer are dire.
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| male bear sleeping by water |
Polar bears are considered aquatic animals because of their lives in and dependence on the water. Their huge front paws are well-adapted to swimming with strong strokes. Until they get close to land, they do not use their hind feet to propel themselves forward. As they near land, they paddle their rear feet much like humans do for the extra acceleration. Reserving that action until the end of their swim saves much-needed energy.
The polar bears do everything they can to conserve energy so their fat lasts throughout the fasting months. They move slowly and carefully. They don’t swim until they’re ready to move to feeding grounds or back to land. This is an essential survival method during their months of fasting. Occasionally, bears will find food, carrion or a bird’s egg or a bird, during the summer months, but this is not common. There is a lot of thinking about how bears could adapt to changing ice conditions, but there aren’t enough birds or small animals to sustain the bear population even if the bears decided to alter their diet and eat something besides seals.
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| mother and cub resting at twilight |
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| cub playing with driftwood |
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