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Updated: November 28, 2011
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| Understanding Prairie Bat Hibernation: Why do bats fly in the winter? |
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By Dr. Cori Lausen, Ph.D. (Biology)  Dr. Cori Lausen, Ph.D. Dinosaur Provincial Park is home to seven species of bats in spring, summer and fall seasons. As part of my doctorate research in the park in 2002-2006, I determined that at least three species of bats over-winter in deep rock crevices in the badlands. Dinosaur Provincial Park was the first natural bat hibernation area discovered in Alberta’s grasslands natural region, some 300 km east of well documented sites in the Rocky Mountains. The rugged badlands landscape provides numerous access points to underground habitat well below the frost line, making the park a strategically important hibernation site for bats. Using acoustic ultrasound recording, I discovered that bats take flight in Dinosaur Park during the winter, at temperatures as cold as -8oC. If you’d like to know more about this research, read the scientific journal publication or BATS Magazine article; or hear the CBC interview about this research (select ‘Hibernating Bats’). Bats have a unique challenge every year. Unlike other hibernators such as ground squirrels that ‘bulk up’ as much as physically possible, bats can’t build up too much fat or they’d be unable to fly! They need just enough fat reserves to make it through winter when there are no insects to eat. 
Big Brown Bat (Eptesicus fuscus) During hibernation bats allow their bodies to cool to a few degrees above freezing, which saves energy and uses very little fat until spring when insects return. Throughout the winter, however, all small hibernating mammals hibernate for a few weeks and then periodically arouse for a short period of time before going back into hibernation. Bats, especially in the prairies, go one step further, flying during these breaks in hibernation. Given that flight uses up a great deal of stored fat, there must be a good reason for these flights. So why are bats coming out of hibernation in mid-winter to fly in freezing cold temperatures in southern Alberta? That is the question that I am now trying to answer. This winter, thanks to a great deal of volunteer work and donations from family and the local community, I resumed research at Dinosaur Provincial Park to test the hypothesis: ‘Do bats need to drink during hibernation?’ Tucked deep into cracks in the semi-desert badlands for the winter, prairie bats might have to venture out occasionally to drink, and may search for a source of open water. Their alpine-based neighbours, roosting in moist mountain caves have an easier time, as cave streams, puddles or condensation provide ready sources of water. A heated water trough (see photo) was installed in the park this winter to test if bats drink during winter. Preliminary evidence suggests this is the case, but stay tuned for more details as the study progresses!  Heated water trough system is to provide an open source of drinking water for bats flying during winter months. Why do we want to know about bat hibernation behaviour? Little is known about small mammal hibernation in general, and even less about bat hibernation. Unfortunately, in eastern North America, bats are dying in very large numbers while they hibernate. Some locations have reported 80% or higher mortality rates. Research on White Nose Syndrome (WNS), a fungal infection associated with the deaths of hundreds of thousands of hibernating bats, is still in its infancy. Understanding WNS, predicting its impact, and developing potential ways of preventing its spread requires that we understand bat hibernation behaviour and physiology. It is my hope that research on natural hibernation of bats will contribute to a better understanding of WNS and small mammal hibernation in general. It may also shed light on potential climate change impacts to prairie bats over-wintering in dry conditions.
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