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GRENFELL MATTERS: Revealing the secret lives of bats — Flying south for the winter?

Dr. Erin Fraser
Dr. Erin Fraser - Contributed

Summer is finally here, and we’re all enjoying these warmer temperatures. It probably won’t surprise you to learn that many animals also favour these temperatures, and travel long distances across latitudes each winter.

You have likely heard about birds migrating south for the winter, but did you know that some bats also migrate long distances each year? There are 18 different species of bats in Canada, and while many hibernate during the colder months, a few species are thought to fly to warmer climates during winter. Bats are small animals and also nocturnal, which means that they are active at night and sleep during the day. As a result, it’s really difficult to observe them in the wild, and we know surprisingly little about when and how they are migrating. It’s important to learn about bats, as many North American species are facing threats and several are endangered. In addition to being beautiful and fascinating animals, many North American bats eat insects and play a really important role hunting agricultural insect pests.

I am a vertebrate biologist who studies bat biology and am particularly interested in learning about how bats move across the landscape. I have worked with Darin Brooks (College of the North Atlantic) and Dr. Fred Longstaffe (University of Western Ontario) to investigate the migratory movements of silver-haired bats in eastern North America. Silver-haired bats are found across much of mainland North America (but probably not on Newfoundland), and are usually thought to be long-distance migrants, who make twice-yearly travels across latitudes. The details of the annual movements of this species are not well known. Many silver-haired bats are killed each year during the fall migration season when they collide with turbines at wind energy facilities at locations across North America. As wind energy becomes more and more common, this kind of bat mortality is increasingly of conservation concern.

In my research, my collaborators and I used a technique called stable hydrogen isotope analysis, which is a type of chemical analysis that uncovers information stored in the fur of animals even after they have died. Tiny fur samples were obtained from bats that died and were stored in various museum collections, including the Royal Ontario Museum (Toronto), the Smithsonian National Museum of Natural History (Washington, DC), and the Field Museum of Natural History (Chicago). Some of these specimens were collected over a hundred years ago. We found evidence that some bats had migrated really far, travelling more than 2,000-km south of the location where they likely spent the summer, while many bats did not migrate nearly as far and some of them may not have migrated at all. One of the most exciting findings was that some of the female bats (but none of the males) who spent the summer in the most northern locations, then spent the winter at the most southern locations, and in doing so, were likely “leaping” over many mid-latitude populations during their migration. For example, several bats that were collected in Florida and Texas likely spent the previous summer in southern Canada. This type of migration is referred to as “leapfrog migration” and is common in songbirds, but this was the first evidence of bats engaging in leapfrog migration. Overall, these findings suggest that silver-haired bats do not have one simple type of migratory pattern, but may vary in their annual movements depending on the population, latitude, and sex of the bat. Understanding the ways that this species moves across the landscape is important for managing and conserving it.

Dr. Erin Fraser is an assistant professor of environmental science (biology) at Grenfell Campus.

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