Bat-box owners wanted: Researchers launch 3-year survey to study health of bat populations

·5 min read
A maternity colony of little brown bats huddles in a bat box found in the Maritimes. (Jordi Segers - image credit)
A maternity colony of little brown bats huddles in a bat box found in the Maritimes. (Jordi Segers - image credit)

If you have a bat box or two on your property, or are thinking of installing one, a group of researchers would like to get a little help from you.

Canada's bat populations have been in decline for years, and researchers believe the lack of good places to roost in summer may be at least part of the problem.

Female bats seek out warm places each summer to pup, typically large old trees with hollows, attics and barn lofts.

They like it hot and humid, but those places are harder to find these days. Decades of commercial logging and urban sprawl has led to a dramatic decline in the number of large trees.

The attics of modern homes are hard for the bats to get into. And, there are fewer old barns in rural areas.

So bat boxes have often been touted as a possible solution.

Bat researcher Karen Vanderwolf is part of a study to survey bat boxes across Canada to try to learn more about their effectiveness.
Bat researcher Karen Vanderwolf is part of a study to survey bat boxes across Canada to try to learn more about their effectiveness.(Karen Vanderwolf/Canadian Wildlife Federation)

They have the added benefit of keeping bats out of the attics of older homes, and can introduce an effective insect eater to your backyard.

But Karen Vanderwolf, a bat researcher at Trent University in Ontario, says little is really known about the effectiveness of bat boxes.

She's part of a three-year study to try to change that.

Partnered with the Canadian Wildlife Federation and the Wildlife Conservation Society, Vanderwolf is looking for citizen scientists from across Canada to provide that information.

"If they already have or are putting one up, we want to know if they have bats in them," she said.

The process is pretty simple. Between May and October, Vanderwolf is hoping bat-box owners could do something called an "emergence survey" at least four times through the summer.

"Just before dusk, take a lawn chair out to where you can see your bat box," she said.

This little brown bat was caught in New Brunswick in June 2019, when researchers did a survey of maternity colonies. Her pup is clinging to her abdomen. Finding healthy mothers and pups in the province is encouraging for a species almost wiped out by white nose syndrome.
This little brown bat was caught in New Brunswick in June 2019, when researchers did a survey of maternity colonies. Her pup is clinging to her abdomen. Finding healthy mothers and pups in the province is encouraging for a species almost wiped out by white nose syndrome.(Karen Vanderwolf/Trent University)

All you do then is wait to see if any bats emerge, and keep as close a count as possible.

If nothing emerges, that's important information too, Vanderwolf said.

If it seems this will take up more time than you're willing to give, Vanderwolf said even a daytime visit to the box to shine a flashlight up into it can at least confirm if there are bats inside.

She's hoping if enough people take part in the survey, the researchers will get an idea of what makes a bat box appealing to a maternity colony.

What we do know is female bats like temperatures between 25 C and 35 C to raise pups, and Vanderwolf said it seems larger boxes with multiple chambers are preferred to small, single chamber boxes.

There have been some reports of bat boxes getting too hot, sometimes reaching as high as 50 C inside, leading to the death of pups.

A bat box on the side of a home in New Brunswick.
A bat box on the side of a home in New Brunswick. (Karen Vanderwolf/submitted)

Some of the people participating in the survey could be asked to place a micro-climate logger inside, which will measure temperature and humidity levels every hour.

Vanderwolf hopes to discover why some boxes get too hot. She said it may have something to do with placement, or the construction of the box, or a combination of factors.

"It's kind of shocking how little information we have here in Canada about bat boxes," she said.

Vanderwolf said they are somewhat controversial in the scientific community, but her personal opinion is that bat boxes can be a useful conservation tool when used appropriately.

And that's especially important, given the state of bat populations.

This bat has White Nose Syndrome, a fungal infection that has killed millions of bats across North America.
This bat has White Nose Syndrome, a fungal infection that has killed millions of bats across North America.(U.S. Fish and Wildlife Service)

Here in New Brunswick, some species have been almost wiped out by a fungal infection known as white nose syndrome, which appeared in the province a decade ago.

So the third part of the bat-box study will seek to find out which species are using them.

People who take part in the survey will be asked to gather bat guano samples using kits sent by mail.

Researchers can identify species from the genetic material extracted from the samples.

It could give scientists an idea of the health of specific bat populations.

COVID-19 pandemic delays research

Vanderwolf said, anecdotally, bats seem to have made a bit of a comeback in the province.

"This past summer, I got lots of emails from New Brunswick about bat sightings," she said, something that had been unusual in previous years.

But scientists won't know more until they are able to do another hibernation survey in caves where bats are known to spend the winter.

Vanderwolf said one was supposed to be done in New Brunswick last year, the first since 2015, but the COVID-19 pandemic put a stop to the field work.

Researchers aren't sure when that survey can be completed. One concern is, given COVID-19 is believed to have evolved in bats, whether North American bats can catch the virus from humans.

Vanderwolf said that possibility has been ruled out in the big brown bat species, but it's still unknown in other species.

If you want to take part in the bat-box survey, there is a short application you can fill out.