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Ballet in the Night Sky

By April 13, 2021 April 15th, 2021 No Comments

After sunset, when the light falls so you can just barely make out the silhouette of trees against the sky, the countryside air may be alive with winged predator and prey. In the TIWLT region, stars of the show are 7 of the 8 species of bats of Ontario. This is a note about one sky dancer, the little brown bat – Myotis lucifugus.

Tiny, a little brown bat weighs in at about the same as 5 or 6 dimes. It looks like a mouse with wings, flies at the pace of a brisk walk, can see ultra-violet light, and hunts by sound too high pitched for humans to hear. Many people first meet these bats if their homes, sheds or barns happen to be a good place to roost during the day. These are colonial critters, and during winter months, colonies would often have thousands, even tens of thousands clustering together. In summer, they are often solitary, hanging out by day in hollow trees, in fractured rocks of cliffs, or caves. 

Photo: Chris Wooding

It’s a myth that bats can eat a thousand mosquitoes in an hour, but the real numbers of several hundred are still pretty impressive. In that night sky, during their hour or two foraging flights, prey might be anything from moths and beetles, to flies and even ants. They’ll patrol an area the size of a small farm, and cruise over hedgerows, swamps and shorelines – any place where there’s good habitat for an abundance of insects. Their calls are about 20 times a second, in millisecond bursts at around 45 kHz.

But it’s not the dance it used to be. The little brown bat was once a most common, widely distributed bat in North America. Today, the population is barely 10% of what it was just 15 years ago. It is now a highly endangered species. A fungus originating in Europe that causes ‘white-nose syndrome’ affects hibernating bats, causing both severe weight loss and elevated carbon dioxide levels in their blood, is taking a horrible toll. 

A couple of summers ago, TIWLT began to investigate bats here, first to see what species are here – more species than previously thought – and now to locate especially important habitat and roosts. TIWLT borrowed sound monitoring and recording equipment for the past tow summer, but now – thanks to a grant from the McNeil Foundation and individual donors, we’re buying our own gear. In past years, we invited people along on evening walks to share the experience. One of the devices translates to ultra-high sounds to what we can hear. Our fingers are crossed that at some point this summer, we can again invite you to come along, and experience that spectacle of the ballet of the bats on TIWLT properties.

Photo: Marnie Ross