Nova Scotia's bat population showing signs of recovery after years of decline

After a decline of over 90 per cent in little brown bats and northern long-eared bats in Nova Scotia, researchers are hopeful the bat population is beginning to stabilize.

A disease called white-nose syndrome caused by a fungus native to Europe and Asia is attributed to the massive decline of hibernating bats in Nova Scotia and New Brunswick since 2011. 

Several bat species found in eastern North America, including little brown bats and northern long-eared bats, have been listed as endangered due to white-nose syndrome.

Karen Vanderwolf, a post-doctoral fellow at the University of Waterloo, told CBC Radio's Mainstreet that these bats have built up an immunity to the fungus. 

"At this point, we're not seeing major mortality anymore of these hibernating bats species," Vanderwolf said. "The ones that have survived seem to be able to tolerate the disease.

"The population has plateaued, and in fact, in some sites in Nova Scotia, in some of the caves, we are seeing a few more bats than we used to see a few years ago." 

She says the fungus was first noticed in New York state in 2006 and spread across the continent. White-nose syndrome only impacts certain types of bats that hibernate in caves and mines during the winter. 

Vanderwolf says the bats are acquiring this fungus on the walls of the caves where they are hibernating. But the fungus has been appearing less frequently. 

"We don't think the fungus is a very good competitor," she said. "There's a lot of other microbes and also invertebrates in these cave sites that probably outcompete and eat the fungus."

She says that despite the signs of stabilization, the bat population could take decades to recover.

"The population can't immediately rebound from this type of mortality because the female bats only have one pup per year, so they can't have large litters to compensate," said Vanderwolf.

How bats help the ecosystem

Bats are a necessity in the ecosystem as they consume hundreds of different insects, including insects that eat crops and human food sources.

Vanderwolf said recent research in the U.S. has found the decrease in the North American bat population has caused a disruption in the ecosystem.

"They found out that this huge reduction in bat populations across eastern North America has resulted in farmers and other workers having to put more pesticides on their crops in order to deal with the insect populations that the bats formerly used to eat," she said.