Building a better home for bats

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To find the perfect hang, bats will seek out cliffs, caves and abandoned buildings. Some may also roost in human-built structures designed just for them.

But not all bat houses are up to chiroptera code.

In hot weather, some structures can get too hot for bats to survive. As climate change increases the frequency and intensity of heat waves, there’s added urgency to make sure bat houses are safe for their tiny tenants.

Now, a new guide has set out best management practices for bat houses in Canada and the United States. The 178-page document, developed by Wildlife Conservation Society Canada with the U.S. Fish and Wildlife Service and the Canadian Wildlife Health Cooperative, was released in November. It offers tips on how to prevent heat-related deaths, discourage predators like cats and owls and mitigate the threat of White-nose syndrome, a deadly fungus that has spread rapidly across Canada and the U.S. since it was confirmed in New York State in 2006.

The report recommends giving bats the option to switch roosts safely as temperatures climb.

“If you put out two boxes, but they’re both facing south, they’re both going to get nice and hot, full sun – which would be great in the spring when the bats really need that heat to go through gestation,” said Cori Lausen, director of bat conservation at WCS Canada and one of the authors of the report. “But those boxes can become little death traps by midsummer when it starts to get too hot.”

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The new report focuses on three species known to commonly use human-built structures: little brown myotis, Yuma myotis and big brown bats.

Once common across Canada, little brown myotis weigh between seven to nine grams and have a wingspan from 22 to 27 centimetres. The species has been listed as endangered since 2014 as a result of White-nose syndrome.

Bats are important for insect control and pollination; one 2011 study estimated the loss of bats in North America could amount to a US$3.7-billion cost to U.S. agriculture.

White-nose syndrome, so named because infected bats look like they have white fuzz on their muzzles, has torn through bat colonies with mortality rates of up to 90 per cent in some locations. This past April, the B.C. government announced the fungus that causes white-nose syndrome had been detected in bat guano in the Grand Forks area, putting bat watchers on high alert for the disease in B.C.

So far, though, it hasn’t materialized, leading researchers to wonder if bats in the West might be affected differently than their eastern counterparts because of variations in genetics, habitat or hibernation strategies.

Bats with white-nose syndrome have been confirmed in 40 states and eight Canadian provinces, according to the website of the White Nose Syndrome Response Team, a U.S.-based group that monitors the disease.

B.C. and Alberta have community bat programs that focus on awareness and education, including appeals for the public to report sick or dead bats.

Such groups also work to buff bats’ image, which tends to be linked with vampires, rabies and coronavirus.

There are more than 1,400 species of bats in the world, but of those, only three are hematophagous, or blood-feeding, and those species are found in Mexico and Central and South America – although research indicates they may move north over time with climate change.

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Bats can carry rabies, a viral disease that attacks the central nervous system of mammals, including humans. Once clinical signs appear, rabies is almost always fatal. Human rabies cases are relatively rare, but health officials urge people not to touch bats with their bare hands and to seek treatment immediately if they are scratched or bitten by a bat.

At a safe distance, bats can draw a crowd. This past April, on International Bat Appreciation Day, the Thompson Okanagan Tourism Association and the B.C. Community Bat Program announced a partnership to help tourism operators co-exist with, and perhaps even promote, their resident bats.

The Okanagan has the highest diversity of bats in B.C., with at least 14 species, TOTA said.

In Peachland, a restored schoolhouse is home to a maternity colony of little brown myotis, with nearly 2,000 female bats and their pups roosting in the attic of the visitor centre every summer. A community group co-ordinates bat-counting sessions as the bats come out to hunt in the evening.

Paula Rodriguez de la Vega, provincial co-ordinator for B.C.’s Community Bat Program, expects more tourism operators to follow suit.

“You can get your glass of wine, or whatever your drink of choice is, and sit outside and watch the bats,” Ms. Rodriguez de la Vega said.

“So instead of being a birder … you’re now becoming a batter.”