9/24/2013 1:14:28 PM
The Northern Giants
Although it may seem like an exaggeration, when getting up close and personal to polar bears they really do seem to be massive giants, and I can't help but feel so small and helpless next to them. I was again reminded of their sheer size when out in the field today searching for bears in Wapusk National Park with fellow researchers Dr. Nick Lunn (Environment Canada) and Michelle Viengkone (University of Alberta). We often weigh the bears using a strong metal tripod and scale - although this time the strength of the metal seemed to be no match for our large adult male polar bear. Lifting its weight (approximately 500 kilograms) caused the metal to warp and our scale to break! Needless to say we did not weigh any more bears that day but luckily had a backup for the remainder of our fieldwork (thank goodness!).
Although females can be quite large as well, an obvious size dimorphism is evident where males can reach up to 800 kilograms while the largest females are around 500. Even though we've encountered many heavy bears during our fieldwork here in Churchill so far, we most definitely still encounter bears that are quite thin, with little fat left on their bodies.
Most polar bears here likely had their last splurge of seal prey around April and May when seal pups are born and very easy to catch (the pups just haven't quite come to understand that they make a delicious meal for a hungry bear!). This high fat diet is used by polar bears to store reserves to sustain them during the long stretch of time they spend on shore. During years when the sea ice melts earlier (by several weeks), bears don't have as much time on ice to feed and may therefore be coming ashore hungrier and with less body fat. Collecting a small biopsy from the rump of each bear, as we've been doing for several years, will not only tell us specifics about the polar bear's diet but can even help us determine if overall body condition (or "fatness") in the same individual and across the entire population has been declining over time and how this may coincide with environmental change.
No matter how tired and sore we may be at the end of our working day from trekking across the rugged tundra or lifting heavy field equipment, it all feels worth it when I realize how unique these animals truly are. Their behavior and life history is completely adapted to an arctic environment and although polar bears are known as the largest of all bear species on Earth, a warming climate is a major threat to their survival. We hope to learn more about how this may be happening and what it could mean for polar bears across the Arctic to better determine ways to mitigate these effects and hopefully allow for the persistence of this magnificent animal!