A new study is out saying that polar bears can likely withstand a longer fasting period on land. An overview of the paper can be found at polarbearscience.com.
I agree with this to an extent. Even though Churchill’s polar bears are out on the ice, they are in fact still losing weight right now. They will hit their lowest weights by spring, just in time to feast on seal pups and young seals that just don’t know any better. When you look at it, the polar bears of western Hudson Bay essentially go with little to no food for about eight months each year – with or without a change in ice patterns.
Right now, denning females with one month old cubs are about six to seven months into their ‘fast’. These bears come off the ice as ultra fat bears and emerge from the den looking skinny and ragged. After that, they will clean themselves, play with the cubs a bit, then walk east towards the sea ice and, hopefully, quickly find some seal birthing dens.
While the fast for pregnant females is not all that different from the conditions encountered by every other bear, it is simply amazing that she can accomplish this while providing the nutritional demands related to raising two fast-growing cubs.
The polar bears’ feast seems to peak in April and May but carries on into July. An early break-up (early June) can have major consequences to the polar bear annual cycle and, therefore, the population.
Basically, an early break-up means less critical hunting time for bears on Hudson Bay but a late freeze-up has a relatively small impact. However, taking into account that a warming climate would likely alter seal birthing patterns (and I believe polar bears would adapt to this quickly), the bears could likely survive in Hudson Bay with only five or six months months of ice, albeit with a reduced population.
Of course, this is based on a gradual change and any extreme changes kind of throw this idea out the window, but it is an interesting thought… regardless, I remain very very skeptical of researchers’ claims of looming extinction in western Hudson Bay.
One month until Watchee Lodge opens and that means one month until mothers and cubs start emerging from the dens! It has been a relatively normal winter with good snow cover. Combine that with a reasonable break-up in late July and there should be a decent ‘crop’ of cubs this year…!
It is time we stopped being complacent about the demise of a species, whether it be gradual or fast. The fact is that polar bears ARE having difficulty reproducing and when they do it is one cub instead of the previous two or three. And as their fasting period extends their ability to reproduce will continue to decrease. Now is the time for the town of Churchill to control the cowboy antics of the Bear Patrol who are armed with rifles which they regularly use to panic the bears as they come ashore. This supposedly is to ensure that there is no interaction between them and humans, but given the fact that Churchill is built across the traditional migration path of the pola bears and the town has done nothing to keep enticing rubbish sealed from behind restaurants and residences, a more sensitive approach would be to build a fence to keep the town isolated. Fences are built along highways and successfully keep the wildlife off. While I was in Churchill a mother bear and her two cubs drowned as a result of the Bear Patrol forcing them with rifle shots back into the raging surf during the blizzard caused by Hurricane Sandy. The time to act is now rather than quoting anecdotal evidence.
Awesome insight. I love reading your blog from the USA and look forward to more. I cannot wait to make it up to Churchill.
Your claim of continued weight loss until the spring harvest of seal pups would put the survival rate of second year cubs close to zero…a bit extreme don’t you think.
Well, its what the studies say… I will find the paper.
Found it… ‘Polar bears reach their lightest weights of the year in late March, just before the birth of the next cohort of ringed seal pups. This fact suggests it is the success of their hunting in spring and early summer that enables them to maximize the body reserves necessary for survival, reproduction, and nursing of cubs through the rest of the year.’ from Stirling, Lunn and Iacozza, 1999