6/6/2016 2:18:42 PM
How Do Polar Bears Choose Where to Roam?
As humans, our homes are very important to us. We might choose to live in homes that are close to schools or grocery stores, or those built high on a hill or down in a valley. Most of us have different ideas about what our ideal home would be-views often influenced by childhood experiences.
Similarly, polar bears have certain preference or needs in their habitats, likely influenced by what they experienced as cubs. If we can better understand how polar bears choose where to spend their time, it may be possible to get a better idea of the most important types of habitat to conserve for them. However, like humans, polar bears are unique individuals with their own preferences. It can be hard to generalize for the entire population.
My MSc project examined polar bear GPS locations collected for decades in Hudson Bay. Along with colleagues from the University of Alberta and Environment and Climate Change Canada, I used these data to look at female polar bear habitat selection across western Hudson Bay (WHB). When I started this project, I knew very little about polar bears, let alone habitat selection analyses. I ended up learning a lot over those few years!
To understand individual habitat selection in this polar bear population, we took the GPS locations for each bear and looked at their habitat characteristics. For example, what was the ice concentration? How deep was the water below? How far was the bear from the coast? We assume that the bear selected for those habitat characteristics.
Then, we took locations available to the bear, but not chosen, and asked the same questions. By finding differences in the selected versus available habitats, we built a better understanding of polar bear preferences or needs, called a habitat selection model.
We recently published our results in Population Ecology. Our study was the first-ever habitat selection model done for Hudson Bay polar bears and the first one for polar bears with the built-in ability to look at individual preferences within the population.
Our findings were not very surprising. Throughout the study, almost all the bears chose the same denning region (most were born there). In addition, they avoided areas with open water or 100% ice (both bad conditions for hunting seals). Individuals were most likely to make dissimilar choices during the dynamic seasons of sea ice freeze-up (fall) and break-up (summer), but made similar choices during the stable, ice-covered winter seasons. Individual bears differed in how far from the coast they preferred to be, the depth of water they preferred to hunt or travel over, and the concentrations of sea ice they chose to travel over.
Recognizing that females within the WHB population select for different habitat features in different ways could help lead us to better conservation plans. In an environment shifting quickly due to climate change, it may be more effective to conserve critical habitats instead of simply average habitats; this could lead to more successful efforts to protect the species long-term.
At the end of the day, polar bears need ice conditions that allow them to hunt seals, but it is important to acknowledge that no two bears are exactly alike. Conservation plans may get complicated in a changing environment, but for polar bears it's all about saving sea ice, something that is very simple. We must lower our carbon emissions and switch to clean energy and that's something we think every polar bear can agree on.