The northern long-eared bat became the latest Minnesota animal named to the endangered species list this week after their stunning and dramatic collapse across the continent over the past two decades.
Two other hibernating bat species — little browns and tricoloreds both — are likely not far behind.
The bats have been almost entirely killed off by white-nose syndrome, a phenomenon caused by a non-native fungus that disrupts them when they're trying to hibernate. The fungus can sprout when the bats slow their immune systems to save energy during the winter. It grows into a fuzzy white moss-like substance that spreads to the tips of their wings and across their faces. The animals wake up to try to lick themselves clean, like a dog or cat. In the effort, they burn through the energy and fat needed to survive winter.
The fungal growth also blocks the release of carbon dioxide, which is done through the bat's wings during hibernation. That again forces bats to wake up in order to exhale, expending precious energy. Sometimes bats die in the cave; other times, they fly off in a hopeless search for bugs to eat in the dead of winter.
The bats are some of the best allies people have ever had. They devour mosquitoes, including at least nine species that carry West Nile virus. A U.S. Fish and Wildlife Service study found that they save American farmers at least $3 billion a year by pollinating crops and eating moths, beetles and other pests.
The fungus has killed millions of northern long-eared bats, wiping out some populations and destroying an estimated 97% in many of their biggest hibernating grounds, such as the Soudan Underground Mine near Ely, Minn. The bat is found in 37 states and much of Canada.
The fungus has killed similar numbers of little brown and tricolored bats. The Biden administration is expected to announce a decision on whether to list those two species in the next few months.
Wildlife managers across the country are shifting strategies in hopes of saving the bats. States have largely given up trying to the keep the fungus out of the caves where they hibernate. They're now focusing on making sure the few animals that have survived can reproduce.
Melissa Boman, mammal specialist for the Minnesota Biological Survey, can hardly hide her excitement when talking about what makes northern long-eared bats special.
They are not the bats that hibernate in houses. Those are typically big brown bats, which haven't been hit as hard by the fungus. Northerns hibernate underground — deep enough to insulate them from a Minnesota winter. They mate in the fall, just as they gather around their caves gorging on mosquitoes and moths to build up fat reserves. The females pause their pregnancy, waiting until spring to have their pups. That's an ideal trait for an animal in Minnesota, where spring weather is so unpredictable, Boman said.
"So if it's a particularly cold spring, they shut things down and put the fetal development on hold until it warms up and there are more insects around," she said.
They need old trees that have deep cracks and crevices to have their pups. Those trees get exposed to a lot of sunlight and keep them warm.
"Aspens and elms are really what they like to use in Minnesota," she said.
The state Department of Natural Resources has been focusing efforts on saving old trees near hibernating grounds. The hope is that the 2% to 3% that survive the fungus can reproduce and that their pups will carry whatever genetic traits may have helped their parents beat white-nose.
Under the Endangered Species Act, landowners and foresters in bat habitat will need federal permits for logging or other actions that could cause unintentional kills. The Fish and Wildlife Service said it will also work with wind energy companies to reduce turbine kills.
The fungus was first documented in the U.S. in 2006 in New York
The fungus was discovered in 2006 in New York, the spores likely carried from Europe or Asia on the clothes or boots of a traveler. It takes about three years for the fungus to devastate an entire state's northern long-eared, little brown and tricolored bats.