When scientist Hugh Broders spoke with The Telegram in 2011, a fungal disease deadly to bat populations known as white-nose syndrome was described as inching its way from the United States toward Atlantic Canada each year.
At least two of three bats in a cave in Nova Scotia show white-nose syndrome. — Photo courtesy of Hugh Broders
“Here in Nova Scotia and New Brunswick, actually, bat populations have been decimated,” Broders, an associate professor with Saint Mary’s University, now says.
Study populations have been wiped out entirely, and others have been reduced by between 90 and 99 per cent.
“So I think the mainland of Nova Scotia has a few bats left but very few. And they probably exist in small pockets here and there,” he says.
A recent article from New Brunswick said a group of 7,000 bats in that province had been reduced to 20. Prince Edward Island populations have also been crushed. Anybody who is creeped out by the flying mammals and thinks a world without them might be less sinister may want to keep in mind that such creatures prey on large numbers of insects.
Canada isn’t the only country experiencing these massive declines. The population plunges are caused by a non-native fungus. Since its arrival at least eight species have been dramatically affected. Those species paying the price are non-migratory species that overwinter in the north. Broders explains that in late summer and early fall bats put on a few grams of fat reserves. Those two to three grams of fat are meant to allow them to get through eight months or so of hibernation. By the end of September, the bats have found a cave or abandoned mine where they spend the winter. Their body temperature drops from about 37 C down to just five degrees or so.
“Then they’re just this cold ball of organic matter, basically,” says Broders.
After two to three weeks, the bats come out of torpor for just a few hours. They start up their immune systems again and drink and/or urinate, and after just a couple of hours, go back into torpor.
A few weeks later, this cycle repeats.
“So there’s this rhythm of about three weeks of down in torpor and briefly coming out; down in torpor and briefly coming out,” Broders says.
The foreign fungus is a cold-loving species and only grows in temperatures of three to 15 C or so. The cool, stable environments of caves and old mines are perfect for them. As the bats hibernate, the fungus grows on the nose, ears and forearms of the animals, causing scarring and necrosis. More devastating, the fungus wakes them up. So instead of coming out of hibernation every few weeks, the bats wake up every few days and are up for hours longer than they normally would be, grooming themselves and trying to remove the fungal growths.
“Because they spend less time in torpor and more time out of torpor, they burn through that 2.5 grams really quickly,” Broders says. “And instead of that fat lasting all the way through to May, it only lasts till January, February, March. Then the animals are in a situation where they’re out of fat reserves. It’s January and minus 10 or 20 outside with a bank of snow, but what do they do?”
If they could eat, they might find a way to survive. But being insectivorous, there’s not a lot being offered up to them in the winter months.
“Then we get all these records of day-flying bats in the winter. We get all these records of hundreds of dead bats at the entrance of caves and abandoned mines. And that’s simply because they’re starving. They’re dehydrated. They’re in a desperate situation,” says Broders.
It’s not entirely known where the fungus came from or how it got here, but scientists believe it likely arrived in New York from Europe prior to the 2005-06 winter when its effects started to be seen. It has since been found in a wide area of Europe where it appears to have originated. There are bats in those areas, too, but the bats there aren’t being affected in any kind of significant way.
“I think the most likely scenario is that this fungus perhaps mutated before there were many scientists around. Ten thousand, 20,000, 100,000 years ago — who knows? And perhaps it became devastating to the bat populations (then), but maybe some of them survived. And then natural selection worked on them then, and then the ones that survived passed on their offspring and then many, many, many generations later the populations were large again.”
That’s speculation. Broders says right now there are a lot of bright people working on the issue, but as of yet there’s no solution and a lot of questions about what will happen next.
That includes what white-nose syndrome has in store for Newfoundland and Labrador. So far there is no record of the disease in the province. The oceanic barrier between the island portion of the province and the mainland isn’t really providing much confidence. Broders says a bat could cross the length of the Strait of Belle Isle in a couple of hours or even from the island to other parts of the mainland. All it really takes is for one bat to bring the fungus over, he says.
So is this province going to experience the same batless fate as its neighbours?
“Hard to say. We don’t know,” says Broders.
As for the places that have already had their bat numbers driven underground, Broders says the best chance might be that ones still alive might have some resistance to the fungus and could be the origins of new populations that will again flourish — just like may have happened in Europe tens of thousands of years ago.
“But not in our lifetime, because these animals are very long lived and have very low reproductive rates,” he says.
In the meantime, people can help with the observation of this province’s bat populations. If anybody knows of a cave or abandoned mine in Newfoundland and Labrador where bats overwinter, they can contact Broders at firstname.lastname@example.org.
Also, if people see bats out flying around between November and March, Broders says they should report it to local wildlife.