The discovery of a large colony of healthy little brown bats is a "glimmer of hope" for the Nova Scotia bat population that has been devastated by white-nose syndrome, said a provincial biologist.

Mark Elderkin, the provincial species at risk biologist with the Nova Scotia Department of Natural Resources, said over the past five years, the disease has killed an estimated 98 per cent of bats from major winter hibernation sites on mainland Nova Scotia.

"In the wake of a 98 per cent projected decline, I think it was totally counterintuitive and surprising that in the last week of June this year we located a site where there are hundreds of female bats and young still present," Elderkin said.

Endangered species

The colony of more than 350 bats was found in an area in the southwestern part of the province that was historically known to have bats, but given the dwindling population numbers, Elderkin said it was was presumed the area's bats had been wiped out.

White-nose syndrome is fatal to most of the bats exposed to it. (Ryan von Linden/New York Department of Environmental Conservation/AP)

"This discovery is really quite unprecedented in terms of the state of white-nose syndrome's progress," he said. "Wherever it has been, usually it's a total wipeout."

White-nose syndrome is a fungal disease that causes bats to develop white patches on their muzzles and other parts of their bodies during winter hibernation. Affected bats wake up early from hibernation and can die from dehydration, starvation and exposure.

Healthy females needed for recovery

Because of the rapid decline in bat populations, Nova Scotia's three species of bats — little brown bats, northern long-eared bats and tri-coloured bats — were added to the provincial list of protected species in 2013.

Elderkin said the discovery, which is the largest known maternity colony in the province, is a sign of hope for the struggling bat population.

"Any future recovery that would come forward in the wake of the disease will always be about how many females are there to reproduce, so every female is more important than ever before now with so few bats remaining," he said.

Importance of bat reporting

​For the last three years, the province has been maintaining a website and toll-free hotline that encourages the public to report bat sightings across the province. Elderkin said they're continuing to collect data that proves there are still bats all across the broad landscape of the province, despite the sharp decline in number.

Bat guano at the site is evidence of a large colony, the Department of Natural Resources says. (Communications Nova Scotia)

"I encourage people to never diminish the importance of every sighting because sometimes people will see a bat on their property once and then a week later they will see it again and they'll think, 'oh I've already reported that,' but now, given the times with so few bats, those repeat observations are even more important," he said.

Elderkin said the next summer, the department plans to use the information collected by the public-generated sighting reports to revisit old sites to see if other colonies are surviving.

To report a bat sighting visit the Nova Scotia Bat Conservation website or call 1-866-727-3447.