White-Nose Syndrome in Great Lakes Parks: Three Bat Species Decline, Big Brown Bats Hold

Some bats hibernate through the winter, living off fat they stored up beforehand. The balance is delicate: a bat without enough fat may starve or leave hibernation too early. That is when white-nose syndrome (WNS), a fungal disease, does its damage — sometimes killing the bat.

The disease

WNS is caused by the fungus Pseudogymnoascus destructans (Pd), which thrives in the cool, humid places where many bats hibernate, and can grow as a white substance on a bat's muzzle and wing membranes.

White-nose syndrome affects many bat species across the United States. NPS Photo / von Linden.

The fungus irritates the skin and wakes the bat, which then burns energy moving and flying — or leaves hibernation altogether before there is food. Since its discovery in New York in 2006, WNS has spread across the country and killed millions of bats.

In the Great Lakes region, five hibernating species are vulnerable: big brown, little brown, Indiana, northern long-eared and tri-colored bats.

The study

Scientists from the National Park Service, North Dakota State University and the University of Illinois Urbana-Champaign published a study of four of those species — all but the Indiana bat — in nine parks from 2016 to 2020: Apostle Islands, Pictured Rocks and Sleeping Bear Dunes national lakeshores; Grand Portage National Monument; Indiana Dunes, Isle Royale and Voyageurs national parks; the Mississippi National River and Recreation Area; and the Saint Croix National Scenic Riverway.

They measured bat populations from recordings of echolocation calls, in two ways:

• occupancy — whether a species was detected at a site at all;
• activity — how often it was recorded.

A Song Meter, used to record bat activity in the parks. NPS Photo.

What they found

Occupancy and activity fell for every species studied except the big brown bat. That suggests WNS is harming little brown, northern long-eared and tri-colored bats, while big brown bats have been hit less hard.

Why is not yet clear. The team looked at factors such as nearby water and tree cover, said co-author Al Kirschbaum, a Park Service GIS and remote sensing specialist, but none of them explained the trends. Even so, knowing which species WNS is hurting will guide further research.

Why bats matter

Indiana bats are listed as endangered, partly because of white-nose syndrome. NPS Photo.

Bats are prey for hawks and owls, eat insects including agricultural pests, and help pollinate many flowers and crops — services that, as Kirschbaum put it, help keep the natural world in order.

People rarely meet bats, beyond the odd one in the attic or a superhero, so they get little attention — and, co-author and biologist Katy Goodwin noted, they are understudied. The Great Lakes parks lacked full information on which bats they had, how their populations were doing, and how WNS was affecting them. This study gives a first baseline for bat conservation there, and adds to research on bats and WNS nationwide.

Sources

Based on "NPS study provides crucial information on White-Nose Syndrome effect on bats," by Clara Deforest Colvig (Conservation Legacy placement with the Park Service's Natural Resource Stewardship and Science Directorate), January 2025, National Park Service; rewritten in hubnx's own words. The author's portrait is not reproduced.