6/23/2014 3:59:19 PM
Why Do Polar Bears Do What They Do?
It's close to that time of year again when the polar bears of Hudson Bay move ashore for the summer, which means it's also time to look back on a very interesting year of tracking our collared bears. This year, each polar bear that we followed chose to do something very different, teaching us a lot about the variety of individuals that we track.
A few polar bears stayed close to Manitoba all year while others chose to travel almost right across Hudson Bay, getting close to Quebec and Ontario. One polar bear even traveled far north to Nunavut with her cubs and back. That's a long round trip!
Each polar bear is different, just like each human is different, so we expect there will be a variety of choices made within a population. Where a bear chooses to travel can depend on age, if the bear is male or female, or if it is a mother with cubs (and, if so, what is the age of those cubs). Some choices may even depend on what the polar bear was taught by its mother when it was a cub.
We don't always know why polar bears choose to do what they do. This is an area of polar bear science that we are trying to learn more about. We do know that the choice of where to travel in Hudson Bay is related to the time of year. There are a couple of critical times during a polar bear's year where we may see some common choices made even among very different bears. One example is during the season when seals are giving birth, or pupping season.
Seals in Hudson Bay have their pups in the spring. One of the main pupping regions is near the west coast of Hudson Bay, north of Manitoba. This year, many polar bears returned to this region during the spring for better hunting opportunities, even those bears that went far out into the middle of the bay in early winter.
When seal pups are young and naÌøve, they are easy meals for a hungry bear and pack a punch of fatty goodness. In areas where there are many seals pupping, a polar bear can expend little energy but get a lot of food—it's equivalent to fast food for humans. This yummy situation draws polar bears in from all over Hudson Bay. It's the main time of year when polar bears build up the body fat that will last them through their summer on land.
Another critical time of year for polar bears is during the sea ice break-up. We don't know when the ice break-up will happen in Hudson Bay this year, but we can see that it's starting now, based on satellite images. We hope the ice stays into July, because if it breaks up a week or two earlier than normal, hunting time is reduced and so is bear body fat.
By now most of our bears have made their way back to the west coast, perhaps preparing to get back on land as soon as the ice concentration gets too low. However, our tracking shows that there is still one bear pretty far north and another off the coast of Ontario. Will these bears return to land in Manitoba before the ice break-up? Will they stay the summer in Ontario or Nunavut (which has happened before)? Or will they just get off the ice in these provinces then walk back to Manitoba? It is a pretty neat thing to be able to track polar bears and their choices, but it will be a long time before we will understand why they make these choices.
One reason we are interested in how polar bears make choices is that we are seeing some shifting conditions in Hudson Bay over the long term, and we don't know how polar bears will respond. Will they stick to past preferences or become flexible as conditions change? Will they follow what their mom taught them or realize they have to do things differently? The answers to these questions could help us prepare for conserving polar bears in the future.
So while many of us look forward to the warm summer months with happy anticipation, polar bears are about to have their favorite time of year draw to a close. Hopefully, they had enough to eat this winter and have enough body fat to live off of this summer. So far we think our collared bears are doing well and hope to spot them and their cubs again this fall. We wish them a cool and short summer and cross our fingers that the ice comes back soon!