Nicolai Haugsted
Deadly bat disease surges north – and scientists fear the worst is yet to come.
Scientists tracking one of North America’s most destructive wildlife diseases have received the confirmation they had long feared.
White-nose syndrome has reached bat colonies in Canada’s Northwest Territories, extending a two-decade advance across the continent into some of its most northerly known wintering grounds. Researchers expected the disease to arrive eventually, but its speed has raised concerns about whether vulnerable populations will have enough time to adapt.
According to The Guardian, laboratory testing confirmed the disease after researchers discovered infected bats near Fort Smith, approximately 725 kilometres south of the Arctic Circle. Scientists had expected another year or two before encountering it so far north.
Millions of bats already lost
White-nose syndrome is caused by the fungus Pseudogymnoascus destructans, commonly abbreviated as Pd. The disease has spread across North America since appearing in New York state in 2007 and has killed millions of bats.
Cold months provide the fungus with an opportunity to attack hibernating animals. Infection damages areas including the face, wings and forearms, disturbing the bats sufficiently to make them repeatedly wake and groom themselves.
Repeated interruptions gradually consume the limited fat reserves needed to survive winter. Dehydration and starvation can eventually follow, with smaller species particularly vulnerable because they carry fewer energy reserves.
Researchers working around Fort Smith have already observed worrying physical damage. Some infected bats showed dying tissue across their wings, while another dehydrated animal discovered near a lake was unable to fly and had wings described as extremely brittle. Unusual daytime activity has also been recorded, which researchers say can indicate illness or attempts at recovery.
Previous outbreaks illustrate the potential scale of the threat.
Caves affected elsewhere have lost around 90 percent of their little brown bats and as much as 99 percent of northern long-eared myotis populations. Some surviving little brown bat populations are showing signs of genetic adaptation that may allow them to conserve energy more effectively during infection.
Prospects appear considerably worse for the northern long-eared myotis. Weighing only about six to nine grams, the species has relatively little stored energy available to withstand repeated disturbances during hibernation.
Researchers warn that the species could disappear entirely from affected ecosystems if mortality in northern Canada resembles losses recorded elsewhere across its range.
Fort Smith carries particular importance because nearby caves include an estimated 3,000 bats. The largest site is considered western Canada’s biggest known hibernaculum and provides winter shelter for several species.
Scientists have not yet recorded the enormous mass deaths previously documented farther south, leaving open the possibility that northern conditions could alter the course of the outbreak.
Temperature could prove important. The fungus thrives at approximately 10C, while parts of the Fort Smith cave system fall below freezing during winter. Pd can survive colder conditions, but researchers believe its growth could be slower there.
Such differences have provided cautious optimism, although researchers cannot yet determine whether the relatively limited mortality reflects the climate or simply the disease’s recent arrival.
Wildfires add another complication. Major fires in 2023 destroyed trees surrounding the caves, forcing bats to travel farther for food, breeding opportunities and suitable summer roosts. Researchers are investigating whether those movements could also have accelerated the fungus’s journey north.
Scientists test possible treatment
Researchers are simultaneously experimenting with an unusual method of helping infected populations survive.
A probiotic treatment developed at McMaster University in Ontario uses beneficial microbes taken from bat-wing microbiomes. Scientists apply the mixture to summer roosts, allowing the microbes to spread naturally between animals.
Early trials in British Columbia and Washington have produced encouraging results. Infected bats carrying greater quantities of the beneficial microbes were found to have lower levels of the destructive fungus, suggesting the treatment could slow its growth and improve survival prospects.
Researchers will return to the caves next spring to assess how the populations survived their first confirmed season with white-nose syndrome. Their findings could determine whether northern conditions have offered the animals some protection – or whether one of North America’s most devastating wildlife diseases is beginning another severe wave of population losses.
