Frozen Toes, Wet Sock, and Icy Boots - Studying Bats in the Canadian Winter


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Bats

Published

2015-02-26

As the pouring rain changed almost instantly to snowfall, I wrung out my mitts and watched the water dent the snow.

I was soaked to the bone but had to keep moving to stay warm. The bats didn't seem to mind the hideous weather. My nets inside the mine complex were dry, but the bats that flew into them were soaking wet. Were they coming in from some other location, or circling in and out of the mine? The small bands that I apply to bats’ forearms to indicate a recaptured individual suggested the latter. But why fly around in such crazy weather? Why fly in winter at all? I have been studying winter bat activity now for more than 10 years, and though I've made much progress, it is hard to solve some of these mysteries.

Finding where bats hibernate is logistically challenging -- small transmitters that can’t be detected very far away means the animals can ‘disappear’ very easily after the transmitter is attached. When we do find places that bats hibernate, accessing these sites in winter almost always involves use of a snowmobile, snowshoes or both. Monitoring such sites has revealed surprising levels of bat flight at cold temperatures outside of their roosts. When I first began examining winter bat activity, it was assumed that bats left their roosts only when facing starvation and in desperate attempts to find food. Now, however, we know that bat flights are common in some species and a temperature of minus eight degrees Celsius or warmer is all it takes for bats to find it warm enough to start flying on a mid-winter night. And while you’d think that the mild winter nights would be when bats are most active, it seems the opposite is true. So if you want to study the bats, you need to brave the worst that winter has to offer. If the temperatures are warmer than -8, and I want to learn something about bats in winter, I don my warm boots, toque and down jacket, and head into the field.

Late last year, as November came to a close in western British Columbia, my muddy boots turned icy. As rain turned to snow, I started to think about how to get the equipment safely out of the site. Luckily we had packed our cramp-ons to get up and down the steep slopes that were now slick with ice, but our four-wheeler slipped around as though it had a mind of its own. Without a doubt, our next field mission to this site would be by snowmobile. As we release our last bat for the night and watch it fly deep into the mine, we all let out a sigh of relief that the night has been a success: 20 bats, three species. We now have more bats banded to determine the total population of bats at this mine hibernaculum. The importance of banding these bats is threefold, and ultimately will help our response to White-Nose Syndrome, an introduced pathogen that is headed our way, killing bats in its wake. By establishing that this is, in fact, the largest bat hibernation site in British Columbia, we can use this site as a sentinel to gauge the impact that WNS will have in this region of Canada. In addition, by developing baseline data on the bat population during healthy times, we will be able to monitor the impacts of WNS and to accurately measure how many bats will die from the disease. Finally, the bands on the bats will allow us to know if certain individuals (sex, age class, and/or species) are particularly affected by the disease.

If this is our most populous bat hibernation site in all of British Columbia, it will be of increasing importance to work with the landowners to secure this habitat for future generations of bats that will undoubtedly face the battle against WNS. Because it is currently our most south-western bat hibernaculum known in the province, we may also first discover the presence of the invasive fungus at this site, making regular surveillance here critical. We have baseline fungal samples to ensure this site is still free of the WNS fungus and we have valuable information about the bats themselves, including their amount of stored fat heading into hibernation, an important piece of the puzzle in predicting whether these bats will be as susceptible to death from WNS. Since bats infected with the fungus that causes WNS use their stored fat reserves far more quickly than uninfected bats, the more fat a hibernating bat has, the longer it could potentially fight off the fungus without starving.

One of our most common and widespread species of bats, the Little Brown Myotis, was listed under Canada’s Species at Risk Act at the end of 2014 and is now considered Endangered in Canada. This listing is a wake-up call that we may have precious little time to learn the most critical pieces of information we will need in order to help save the 15 species of bats that hibernate in western Canada. How will our forests, crops and gardens fare if the natural pest control services by bats are drastically reduced?

As I reach for another toe warmer pack to stuff into my boots, and unload my gear from my truck at the end of the night, preparing to defrost and then dry everything, I think that the road to understanding winter bat ecology is a long one, but I am determined to keep moving forward before the deadly WNS arrives. It is this hope that keeps me moving forward with my research each day, in spite of the frozen toes, wet socks and icy boots. We need our bats, and now, more than ever before, they need us.

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