Hi Gordy – that is a good question. I am looking for a mammal book that describes the senses of a seal. I would imagine sight and sound are pretty important, but I hope to figure it out soon.

Thanks for the question. It is true that some non-profit environmental organizations put out advertisements that are quite dramatic. In the interest of full disclosure, our project is principally funded by the National Science Foundation, but we have received limited support from World Wildlife Fund (WWF), an organization that has a focus on polar bear conservation.

The main threat to polar bears is loss of sea ice due to climate change. Polar bears rely on sea ice for traveling, hunting, and in some places, digging dens and giving birth. Arctic sea ice is declining in extent. Every year the ice melts during the summer and refreezes during the winter – this is a normal pattern. However, currently, every summer the melt is becoming greater. This means that polar bears can spend less time on the ice, and the ice may not be found in areas where it once was. This can prevent bears from traveling, hunting, and in some places, digging dens.

It is impossible to be sure how bears will be affected by the loss of sea ice. However, there is a high probability that polar bears will be strongly negatively affected, and some effects are already occurring. For example, a recent study found that the population of polar bears in western Hudson Bay, Canada, declined by 22% from 1984 to 2004, and that the decline was closely associated with earlier breakup of sea ice in the spring (Regehr et al. 2007; see citations below). Similarly, a recent US Geological Survey study concluded that climate change and reduced sea ice could lead to the loss of 2/3 of the world’s polar bears in the next 50 years (USGS 2007).

It does not seem to be that the food sources of polar bears are dying off, but rather that the distribution of the bears and the food sources are changing, making it harder for polar bears to find their food items.

As the summer ice melt becomes more dramatic, polar bears in some places may be forced to spend more time on shore. Their main prey are seals, which generally aren’t found on shore, thus, the bears may eventually starve. We are not sure how long polar bears can go without food (this is one question we are studying). Some polar bears follow the ice north during the summer, but if the ice melts too far to the north over deep water, seals may not follow the ice. Thus, bears on the ice may face a similar situation as those on land. A recent study in northwestern Canada found that polar bears captured in 2005-06 were more likely to be fasting (going without food) than those that were captured in 1985-86 (Cherry et al. 2009).

Currently, it is not clear whether polar bears are drowning more frequently because of the loss of sea ice. There have been some well-publicized cases of bears seen drowning in open water, but there is not enough data to draw strong conclusions. It is probable that reduced sea ice will cause bears to swim more often and for longer distances. However, polar bears often walk and swim over huge distances, and it is difficult to ascertain whether they are swimming more and if this presents a danger.

It is also probable that as polar bears have more difficulty finding food items, they will look for food around human habitats more often. A recent study concluded that increases in bear encounters in some parts of Canada were likely related to food-stressed bears seeking items to eat (Stirling and Parkinson 2006).

Overall, although many questions remain it is clear that climate change and the loss of sea ice present a serious danger to polar bears, and it is likely that polar bear populations will continue to decline. A summary of how bears will likely be affected by loss of sea ice is presented by Derocher et al. (2004).

Because I am in a scientific position, it is difficult to recommend any specific conservation action, such as supporting a particular environmental group or practice. However, I will say that climate change is a very real problem, and it has very serious implications. To me, the heart of the issue seems to be how we generate the power that runs everything from cars to toasters, and how we use or abuse that power. Internationally-coordinated efforts are needed, but so are individual actions. Climate change is a human problem that is affecting the world, and every individual that recognizes the problem and addresses it in their life will make a difference.

Take care,
John

Citations:

Regehr, Lunn, Amstrup, Stirling. 2007. Effects of earlier sea ice breakup on survival and population size of polar bears in western Hudson Bay. Journal of Wildlife Management 71:2673-2683.

USGS (US Geological Survey). 2007. USGS Science to Inform U.S. Fish & Wildlife Service Decision Making on Polar Bears, Executive Summary.

Cherry, Derocher, Stirling, Richardson. 2009. Fasting physiology of polar bears in relation to environmental change and breeding behavior in the Beaufort Sea. Polar Biology 32:383-391.

Stirling, Parkinson. 2006. Possible effects of climate warming on selected populations of Polar Bears (Ursus maritimus) in the Canadian Arctic. Arctic 59:261-275.

Derocher, Lunn, Stirling. 2004. Polar bears in a warming climate. Integrative and Comparative Biology 44:163-176.

On Cable TV, BRAVO channel I see these dramatic commercials put out by the Natural Resources Defense Council about the bears starving and drowning and wonder if they’re merely motivated to profit from the plight of the bears or are their alleged efforts to fight the US Government to “give the polar bear and its Arctic habitat full-fledged protection” a worthy cause?

Are these bears starving? Is it because they can no longer find food? Has their food source died off or migrated too far away from them? Are they drowning?

Is there an increase in bears looking for food around human habitats? I read a story of a researcher in Svalbard, Sweden just recently had to kill a polar bear whom had nothing in his stomach. http://www.adn.com/life/alaskana/story/845908.html

I find this all very sad and disturbing and would like to help any way I can–what can someone like me do? Thanks for your time.