NPS study provides crucial information on White-Nose Syndrome effect on bats.

By Clara Deforest Colvig, January 2025

Like many mammals, some species of bats assume an inactive state of hibernation each winter. Beforehand, they eat as much as possible to build up fat and provide themselves with enough energy, then slowly burn through it over the course of the winter. This is a delicate process; if a bat does not have enough fat stored, it risks starvation or emerging from hibernation too early. It is during this crucial biological function that White-Nose Syndrome (WNS), a fungal disease, can cause extreme harm or even death in a variety of bat species.

To combat this disease and help save our vulnerable flying friends, it is important to understand the extent to which WNS is affecting bats and what bat populations look like right now in terms of species and numbers.

National Park Service (NPS), North Dakota State University, and University of Illinois Urbana-Champaign scientists, recently published a study on the status of four bat species in nine Great Lakes region parks. Keeping an eye on vulnerable species is important for making smart decisions about resource management and conservation.

What is White-Nose Syndrome?

WNS is caused by Pseudogymnoascus destructans (Pd), a fungus that thrives in cool, humid environments, the same environments where many bat species prefer to hibernate. Pd can infect a bat and grow a white substance on its muzzle and wing membrane.

WNS affects many different bat species all across the United States.

NPS Photo / von Linden

The fungus irritates the bat’s skin, awakening the bat from hibernation. This can cause it to warm up and waste energy by moving around and flying or cause the bat to fully emerge from hibernation before food is available for it.

Since being discovered in 2006 in New York, the disease has spread across the United States, killing millions of bats.

In the Great Lakes region, there are five bat species that hibernate and therefore are susceptible to WNS: big brown, little brown, Indiana, northern long-eared, and tri-colored bats.

The Study Detects Declines

The study assessed population trends of four of those species – all but the Indiana bat – in nine national parks from 2016 to 2020. The parks were: Apostle Islands National Lakeshore, Grand Portage National Monument, Indiana Dunes National Park, Isle Royale National Park, Mississippi National River and Recreation Area, Pictured Rocks National Lakeshore, Saint Croix National Scenic Riverway, Sleeping Bear Dunes National Lakeshore, and Voyageurs National Park.

Scientists used two ways to measure bat populations based on recordings of the bats’ echolocation sounds: occupancy and activity. Occupancy refers to the physical space the bats use. Activity refers to how often bats make sounds or use echolocation.

Scientists used a device called a Song Meter to detect bat activity in parks.

NPS Photo

Biologist Katy Goodwin, a co-author of the study, said when measuring occupancy they asked, was a certain bat species detected or not? When measuring activity they asked, how frequently were they recording a certain bat species?

Results showed declines in occupancy and activity for all species studied except the big brown bat. This suggests that WNS is harming little brown, northern long-eared, and tri-colored bats, but big brown bats have not been as strongly impacted.

Scientists are not sure what is causing this variance. “What could possibly explain the decline or increase in bat populations? We must ask, how much water was nearby? What was the tree landscape? But none of the trends we saw were explained by these variations,” said Al Kirschbaum, an NPS GIS and remote sensing specialist, and co-author of the study.

Even without an explanation of the cause, understanding the effects of WNS on certain bat species will help guide future research.

Bats are Important

Bats are essential for the role they play in food webs. For example, bats are prey for raptors such as hawks and owls, they consume insects such as agricultural pests, and they are vital to the pollination of many flowers and crops.

Indiana bats are listed as an endangered species, partly because of the effects of WNS.

NPS Photo

“Bats provide ecosystem services. They help with anything from pollination to maintaining healthy insect populations,” said Kirschbaum. Pollination and insect control help keep the natural world in order.

Goodwin noted that because humans typically do not have many personal encounters with bats, besides the occasional bat in the attic or superhero reference, people may not be curious to learn about them. As a result, she said, bats are an understudied species.

Because bats are understudied, the Great Lakes parks had incomplete information about the bat species living in the parks, the status of their populations, and how WNS was affecting various species. The study provided crucial, initial insight for how humans can better understand bat conservation.

“The wealth of knowledge we have learned will contribute to the larger science community of research on bats and WNS around the country,” Kirschbaum said.

Clara Deforest Colvig
Clara Deforest Colvig is a recent graduate from Colorado State University. She works in the National Park Service’s Natural Resource Stewardship & Science Directorate through a Conservation Legacy individual placement.