From threatening humans to eating their own, polar bears struggle with climate change
The Canadian Press |
Dec 17, 2011
They're etched onto Canada's coins, are part of the country's national identity and lure tourists to the Arctic every year, but the majestic Canadian polar bear could pose a significant risk to northern communities if climate change continues to wreak havoc on its natural habitat.
"It's potentially quite serious in terms of human-bear interactions," says Ian Stirling, an Edmonton-based scientist with the Canadian Wildlife Service who has studied polar bears for 41 years.
"It's a big problem in northern communities, it already is. They're killing 30, 40, 50 problem bears a year in the Canadian Arctic because they're threatening human life or property."
The adjunct professor at the University of Alberta wants to drive home the point that action is needed to combat the climate change which has the potential to turn the typically mild-mannered mammals into a risk.
As Stirling details in his new book -- "Polar Bears: The Natural History of a Threatened Species" -- the biggest threat to the bears is an increasingly warming climate which is causing earlier and more wide-spread melting of northern sea ice.
The ice is crucial to the bears because it serves as a hunting platform to access their primary food sources -- particularly ringed seal pups. With the ice breaking up earlier over time, bears lose precious opportunities to gather food.
"If they can't eat, they're not going to survive," says Stirling.
Polar bear cannibalism?
In startling new research, scientists are now also suggesting bears are turning on their own young in some cases to satiate their hunger as climate change hampers their feeding patterns.
"We are seeing a great deal more cannibalism and infanticide in the last 10 years more than we've seen in the last 25 or 30 all put together," says Stirling, who recently co-authored a paper documenting the issue in four cases.
While starving adult males have been known to prey on younger polar bears on occasion, what's new is the killing of small bears when the older predator is still fairly healthy.
While more study is needed, Stirling says the issue could be a case of young cubs being one of the few accessible sources of sustenance after the early break up of sea-ice.
Meanwhile, Canadian polar bears — which make up two-thirds of the global population — are being affected by climate change at such a fast rate that those living on the shores of lower Hudson Bay could disappear in just a few decades.
"The situation in Manitoba and Ontario is really pretty serious," says Stirling, who adds that sea ice is now breaking up three weeks earlier than it was 30 or 35 years ago, which leads to leaner bears and lower birth rates.
"Thirty, 40 years from now, there probably won't be many bears left in Hudson Bay."
Polar bears: The canary in the mine
From a wider perspective, Stirling argues that attention should be paid to the plight of the polar bears because the animals are a very real marker of effects of climate change.
"Polar bears are very representative of the kinds of things we're seeing in climate change," says the 70-year-old. "What they're also telling us is that we're not going to have the Arctic the way that we're familiar with it."
To preserve the species and the country they live in, Stirling urges the average Canuck to take any small step to can protect the environment and pressure politicians to force a reduction of greenhouse gas emissions.
"The longer we hold off and don't do something about these things, the greater the negative effects and costs are going to be for our children and our grandchildren."
Stirling's words seem to strike a chord with those who hear him speak.
"We are on the verge of losing Canada's greatest heritage," said Robert Buchanan, chief executive of Polar Bears International, which hosted a lecture by Stirling in Toronto.
"If Canada doesn't care about the Arctic and it's polar bears, why should the rest of the world care?"
A long time ago I took a course on bear behavior and I remember being told then that the single largest threat to a bear cub of any species is a male bear of that same species. Seems pretty well documented that the male bears kill the cubs so that the female will go into heat sooner. This is also why females are protective of their cubs.
In the fourth paragraph, Stirling characterizes polar bears as "typically mild mannered mammals". I've heard many descriptions of polar bears, but I've never before heard them referred to as "typically mild mannered mammals". It makes Stirling's conclusions suspect.
What is the population of polar bears in the Canadian arctic? A quick website search shows several articles about a growing polar bear population in Canada. Wouldn't a high population of hungry polar bears also be a cause for cannibalism?
You might read the piece more carefully. There are no quotes around that paragraph is there are for the one before it where Stirling says humans are “killing 30, 40, 50 problem bears a year in the Canadian Arctic because they're threatening human life or property." The “typically mild-mannered” description is from the unidentified writer for the Canadian Press, a news agency like AP or Reuters.
While you’re at it, you might check the accuracy of your sources. The Polar Bear Specialist Group, charged with monitoring the bears under the treaty signed the early ‘70s by the 5 countries with coasts on the Arctic Ocean would be a good place to start. They report numbers for 19 sub-populations (sort of like herds but looser). In there last report in 2009 they estimate, for the sub-populations that range all or party in Canadian territory: declines numbers for 7 groups totaling ~3,800 animals, stability for 3 (~3,500), increases in 1 (~300), and insufficient data on 3 (~2,200).
Recent anecdotal reports of greater bear sightings are do to bears spending more time on land, where they are more easily seen, as they try to cope with the longer periods of no ice, not an increase in the number of bears.
The net is full of cherry picked claims of greater bear numbers based on population growth from a total of ~5,000 in the early ’70s to 20,000 -25,000 at the turn of the last century. That growth was due to the end of almost all sport hunting. More recently, the overall numbers appear to be declining due the strain caused by reduction in habitat and by poaching.
Gee I wonder if they will adapt? Darwin thought that's what happens. Or is it divine intervention? That's the theory the Christians adhere to. Me I'm gonna bet Darwin is right. Of course that would tend to disprove the global warming "End of the World Theory" Won't it?
A huge amount of species are going extinct, as climate change for instance, far outpaces their ability to adapt, their habitat is being destroyed or radically changed, or the arrival of non-native species, especially predators, are wiping them out. We are the most effecient of those predators, so are wiping out land and sea species. In the paper you quoted below it explains the extinction of various fauna, especially megafauna in the Americas, due to human predation and habitat change. Hence the disappearance of horses and larger, less adapted bison from the North Slope and the proliferation of caribou as habitat chnaged from steppes to tundra-tussocks.
Since you know this, one would presume you are merely being argumentative.
Our concern is not the "end of the world 'theory'," but the "end of the world as we know it due to human influence."
The American Bison didn’t seem to adapt rapidly enough to survive in anything like there former numbers (~30,000 “wild” and 500,000 “stock”) of 60 to 100 million circa the mid-19th century. Current numbers are up many, many times the animals around in the 1890s and have a lack of genetic diversity since so few survived into the 20th Century. The Passenger Pigeon didn’t survive at all despite once numbering 3 billion to 5 billion. On flock, a mile wide and 300 hundred long, seen the year after the civil ended, was estimated in the billions. A $3,000, "real money" for the tine, was offered during the period 1909 to 1912 for a living specimen. It went uncollected. The last known bird died in 2nd Month of WW 1.
Evolution is a lengthy process for animals with low birth rates. Loss of habitat due to human’s wasteful ways, or humans just directly killing them faster than they can reproduce, doesn’t make much difference.
Strange how your posts are so free of the important facts of an issue, but sometimes have a few that are true in themselves. Sort of like bricks of pork lard with packaging advertising no sugar added.
And of course the most important part of your argument is that Humans are not part of the environment right? And of course there is no chance that this generation of those bears are going to adapt to the changes in their environment. They are not going to change their feeding habits and start looking for food inland? Never mind that one was killed at Ft Yukon a couple of years ago.
Your post is confusing. The fact that humans are an important part of the environment is part of Oldhat's arguments. Your second sentence is very correct because polar bears are slow reproducers (in comparison to muskrats) and one generation of bears is not going to adapt to the lack of ringed seals. While one or some polar bears will remain on land, most will swim toward where ringed seals and the pack ice used to be...and quietly drown.
An odd argument to make since we are talking about a bunch of bears that have remained ashore feeding on whale carcasses left by human hunters rather than swim off and commit suicide looking for ringed seals. That Behavior looks an awful lot like an adaptation to me. Whether or not it is successful is something that time will certainly tell. But remember, these white bears have not always existed, they and the brown bears on Admiralty Island share a common ancestor that has been long extinct and both are strikingly different adaptations to changes in their environment that more than likely had a big part in the rapid extinction of their ancestor.
The features that the polar bears have developed through evolution may not and probably will not serve them well if they had to move inland. Warming is far outpacing the ability of the species to adapt.
I knew of a hunter who killed a polar bear inland near Atqasuk about 15-18 years ago. That's about 50 miles from the Arctic Ocean. The one that showed up in Ft. Yukon was five times as far from the sea. I suspect that both bears were damaged somehow, disoriented, through age of disease and just kept plodding south instead of north.
You're missing the point. Oldhat said, "Evolution is a lengthy process for animals with low birth rates." The changes in the environment when the common ancestor of polar and brown bears lived, took place over hundreds of thousands of years. The shrinking of the polar icepack in a few decades does not allow enough time for polar bears, with low birth rates, to evolve or adapt genetically. When they cease to exist, their gene pool will be gone forever.
Feeding on a whale carcass will not lead to polar bear populations surviving and reproducing by hunting whale carcasses.
Many people think that oldhat is incorrect in his assessment of evolution. there is a lot of evidence that it is a process that can occur swiftly in some cases even when birth rates are very low. let me refer you to PAGE 46 of a scientific study called;
..............................................................
The Mesa Site:
Paleoindians above the Arctic Circle
Michael Kunz, Michael Bever, Constance Adkins
"It would be difficult to find a time period
containing more radical shifts in climate,
vegetation, and biota than the several millennia
spanning the Pleistocene to Holocene
transition. Most intense was the period ca.
11,000 to 10,000 years BP, referred to as the
Younger Dryas, a time when global climate
jumped from interglacial conditions to glacial
conditions, then back to interglacial conditions
with decadal rapidity (Alley et al.
1993; Mayewski et al. 1993; Isarin and
Bohncke 1999; Alley 2000). Widespread extinctions
affected the world’s megafauna
during this interval (Martin and Klein 1984;
Guthrie 1990). The flooding of Alaska’s continental
shelves, particulary after ca. 10,000
years BP, had significant impacts on climate,
and vegetation changes repeatedly swept
through arctic Alaska."
...............................................................
As you can see the climate has had prior period of very dramatic shifts on other occasions and as noted, many species became extinct. More interesting, MANY DID NOT some how they managed to either evolve or adapt.
Then “many people” are wrong in their thinking, but that's hardly surprising. Nothing in the paper you cite speaks to biological evolution, a subject - along with several others, it is becoming evident that you have only a faint grasp. What it does speak to is ecological change. Individual species: moved-in, moved-out, coped, or went extinct.
You continue to use evolution as a plausible argument, it being the one you started with. That isn’t in the cards on the relevant time scales. What’s left is the bears adapting their behavior; their genetically inherited capacity for behavior adaptation is large. They are quite good at finding something to eat, like most bears. Trouble is, there’s precious little to eat on the land in the Arctic. Hand waving that they will adapt to other food sources is just that - hand waving.
Food for Eskimos, Inuit and polar bears comes from the sea. Polar bears, a bit more specialized than Arctic dwelling humans who can take whales and, much more easily take a walrus than the bears, use the ice to get at seals that make-up the great bulk of their food.
The general consensus of those with way more knowledge of the subject than both of us, gained from actually studying the critters, is the bears will exist into the next century as a remnant population, probably of a few hundred animals in the northern Canadian Arctic Archipelago and very northern Greenland, and in zoos. That’s not a good situation for them to be in. The examples of Binky and Nuka at the Alaska Zoo having no issue with more then 10 years of opportunity and then dying of a parasite, or the bear ranging to Fort Yukon (you mention he didn’t survive) are cautionary.
On the Younger Dryas. Ya, big and rapid changes in climate, but the effects were greater on the land, and for the bears, there was rather little change in the area of sea ice where they feed. The devil’s in the details. The extinctions that occurred at that time are attributed to various causes, with changing climate a large factor in all of them. See:
Notice there’s no mention of marine species. Polar Bears are identified as Ursus maritimus (sea bear) in the Latin of formal species naming for a reason.
Really? The effects of the climate changes were greater on land? Why are we being told that this time that the climate changes there will result giant changes in shorelines massive flooding and significant ice cover changes? You fail to show why this time should be significantly different than the previous examples. (Damn those devilish details)
Oh by the way many scientists believe that the Ursus maritimus is not even a ditinct species of bear rather a phase of the common north american brown bear Ursus arctos horribilis.
Thanks for the citation. I read the whole thing, about 80 pages, and found it very interesting.
However, you've misread it. There were weather fluctuations that changed the environment enough that the dominant species diminished or disappeared or were replaced by others, i.e., Mammoths and bison by caribou. The animals disappeared thanks to loss of habitat, or simply moved to where the pickings were better. You've misread the study to assume that this happened far more rapidly than it and that it was all part of a rapid evolutionary process.
If you look what happened to mammoths that were isolated by rising seas 12,000 years ago on Wrangell Island, or even Catalina Island off Los Angeles, they evolved over a period of many thousands of years when their massive size was no longer needed to resist predation or was a liability due to a diminishing food resource. There was a similar process in Indonesia with a close relative.
Perhaps I did misread it. Can you explain the following excerpt:
(The Caps are mine)
"a time when global climate
jumped from interglacial conditions to glacial
conditions, then back to interglacial conditions
with DECADAL rapidity"
(this indicates to me that very significant ten year cycles were happening then. In fact, by description they were far more extreme than what we see now.)
I am also suspicious that the same thing will happen in the arctic as happened then, As the climate changes and warms, the arctic supports far more life ashore and many more larger mammals exist inland than in cooler times. That was why the people who lived there then did live there and when it cooled and the food source died out they were force to move or die out as well.
In both cases this is a nearly perfect example of evolution in action if you look at evolution as a systemic thing that can also sometimes be observed in individual species.
This is not my science, It belongs to these good fellows. It does present a very interesting read when looked at in light of climate change and it's net effects. Please note that Human Activity is clearly not to blame in this instance. I do not attempt to argue whether or not the climate is rapidly changing, I do believe that there is not one thing that mankind can do that would even slow the change and further am very skeptical that our involvement has had anything to do with causing the change to occur.
You should read the entire study even though it may take a bit of time. I warn you it is a difficult read, it does have some "big" words but those that give trouble can be deciphered using any decent reference.
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