After years of a brutal killer fungus, bats in N.B. are showing signs of resilience
White-nose syndrome resulted in the loss of 99 per cent of hibernating bats across the province
Nearly 14 years after white-nose syndrome began devastating bat populations in New Brunswick, researchers see signs the fungus is receding and bats are becoming more resilient against the disease.
Karen Vanderwolf, a postdoctoral fellow at the University of Waterloo, was a conservation specialist with the Canadian Wildlife Federation and the New Brunswick Museum when the fungus was discovered in New Brunswick in 2011.
"We were very concerned," Vanderwolf told Shift. "We had heard about the disease and what it was doing in the northeastern United States."
Vanderwolf said the fungus — Pseudogymnoascus destructans — that causes white-nose syndrome spread to the Maritimes faster than expected and resulted in the loss of 99 per cent of hibernating bats across New Brunswick.
"When we were approaching a cave in March of 2011, and we saw all of these dead bats in the snow we knew exactly what we were facing and how devastating it was going to be," she said.
In 2012 and 2015 researchers swabbed bats and walls in caves around the province to collect samples of the fungus, Vanderwolf said.
"It was very easy to detect the fungus and grow the fungus in the lab," she said.
That study was done again in 2022, but this time, the fungus was much more difficult to find in caves.
"We only found two cultures of the fungus … so a very big decrease in pathogen prevalence in these sites, which is really great news," she said.
In 2012, more than 40 per cent of swabs collected contained the fungus. That number dropped to 35 per cent in 2015.
In 2022, only two of the 120 swabs collected contained cultures of the fungus, representing a 1.7 per cent prevalence rate.
"These bats are the survivors who have gone through this bottleneck with the disease, and they seem to be able to tolerate it at this point," she said.
Vanderwolf said the fungus targets bats and doesn't compete well with other microbes in caves.
"it seems to be just out-competed by other microbes, and with the bat population decreasing so much, it doesn't have much of its preferred food source."
While bats are still dying, Vanderwolf said the deaths are now happening at normal rates, and researchers consider the population to have "plateaued."
The study shows a decrease in the fungus that causes white-nose syndrome in both New Brunswick and Nova Scotia.
Vanderwolf is now working to see if the fungus is decreasing elsewhere in eastern North America. It was first spotted in the state of New York in 2006 and spread from there.
Why were bats vulnerable?
Vanderwolf said bats don't eat all winter while they hibernate. To prepare their bodies for many months without food, they drop their temperature and reduce their energy expenditure by down-regulating some of their systems, including their immune system.
"So they are kind of vulnerable hibernating in these caves to a pathogen that can also survive in these caves like the fungus that causes white-nose syndrome," she said. "So we had this naive population who have never encountered this pathogen and it just devastated those populations."
As of 2011, there were three bat species in New Brunswick that hibernated in caves — tricolored bats, little brown bats and northern long-eared bats.
Vanderwolf said white-nose syndrome hurt all three species, but especially the northern long-eared bat and the tricolored bat.
"In fact, in New Brunswick, we haven't seen a tricolored bat since 2013."
She said the big brown bat population has continued growing over the last 10 years, and now that species will spend time in caves, which it didn't do before.
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With files from Shift
