Threats to Lake Superior’s “Invisible Mammal”
- NPLSF
- 19 hours ago
- 5 min read
Updated: 4 hours ago
Learning about bats from scientist Dr. Winifred Frick
For residents of the Lake Superior region, bats have long been familiar summer companions—swooping through twilight skies and occasionally taking shelter in barns and attics. But over the past two decades, these nocturnal mammals have faced catastrophic population declines, raising concerns about both ecological balance and agricultural sustainability.
Dr. Winifred Frick, Chief Scientist at Bat Conservation International and Adjunct Professor of Ecology and Evolutionary Biology at the University of California, Santa Cruz, has spent 25 years studying these remarkable creatures. Her research has revealed the scope of challenges facing bat populations and offered glimpses of potential solutions. She has also shared her research in a fascinating new film, The Invisible Mammal.
Listen to the full episode and read more below.
The Ecological Value of Bats
Before understanding what threatens the Lake Superior Region’s bats, it's essential to recognize their critical role in local ecosystems. All North American bat species are insectivorous, consuming vast quantities of insects nightly. This dietary preference provides significant benefits to agriculture and the environment.
Research conducted in Midwestern cornfields has demonstrated this impact dramatically. Scientists constructed large nets over corn crops and measured pest damage with and without bat foraging. The results were clear: fields protected from bats experienced substantially more crop damage from agricultural pests.
"Bats provide billions of dollars to the U.S. agricultural economy in terms of the number of crop pests that they eat," Dr. Frick explains. "And if they're not eating those crop pests, then farmers have to put on more pesticides. It not only costs them money, but also does other kinds of damage to our environment."
Similar studies conducted globally—examining cotton in Australia and rice in Spain and Thailand—have reinforced these findings, demonstrating that bat conservation has direct economic implications for farming communities.
Lake Superior Bat Species and Their Behaviors
Approximately 47 different bat species call the United States and Canada home, with several species inhabiting the Lake Superior region across Michigan, Wisconsin, and Minnesota. These small mammals possess remarkable characteristics that distinguish them from other wildlife. Despite their diminutive size, bats can live extraordinarily long lives—some Siberian species have been documented living over 40 years.
The region's bats exhibit fascinating seasonal migration patterns. During summer months, they roost in trees, barns, and under bridges, where female bats gather to give birth and raise their single annual pup. When winter approaches and insect populations disappear, bats move underground into caves and abandoned mines throughout the Upper Peninsula and surrounding areas.
There, they enter hibernation, utilizing a unique mammalian ability to dramatically slow their metabolism. "They literally chill out in the winter and they go cold to save energy," Dr. Frick notes. Bats remain in this torpid state until May or June, when warming temperatures and returning insect populations signal the time to emerge.
The White-Nose Syndrome Crisis
The most devastating threat facing our area’s bats emerged in upstate New York during the winter of 2006-2007. White-nose syndrome, caused by the fungal pathogen Pseudogymnoascus destructans (abbreviated as Pd), has since killed millions of bats across eastern North America.
The fungus grows on bats' skin tissues—their wings, tail membranes, ears, and muzzles—creating the characteristic white fuzz that gives the disease its name. Historical photographs of hibernating bats never showed this white growth until that fateful winter, just before populations began crashing.
The fungus spreads both through direct contact between bats and from contaminated cave and mine surfaces. Once infected, bats experience a disrupted hibernation cycle.
"The fungus causes them to burn up their energy reserves during the long winter," Dr. Frick explains. "That infection causes them to arouse too frequently from that torpor state that is really energy saving. And then they burn up their fat reserves trying to fight off the fungus and then they starve to death before spring."
The disease reached the Lake Superior region approximately a decade ago, with catastrophic results. The little brown bat, once one of the region's most common species, has seen dramatic population declines. The northern long-eared bat has fared even worse, experiencing a 99% population decline that resulted in federal endangered species protection. The tricolored bat, another regional species, has also been severely impacted.
Conservation Efforts and Innovation
Researchers have spent nearly two decades developing strategies to combat white-nose syndrome. Scientists at the USGS National Wildlife Health Center in Madison are working on a vaccine showing promising results. Other efforts focus on neutralizing or eliminating the fungus from caves and mines, though this approach requires extreme caution to avoid harming other cave-dwelling organisms.
Dr. Frick and her colleagues have pioneered an innovative approach they call the "fat bat project."
The concept emerged from observations that surviving bats in white-nose-affected areas tended to enter hibernation with higher fat reserves. Working near the Delaware Mine and other abandoned mines near Houghton, Michigan, researchers installed UV lights that attract insects bats prefer to eat.
The results were encouraging. Bats increased their foraging at these illuminated areas both in fall before hibernation and in spring after emergence.
"Our hope is that it's a simple action that we can take that can basically give the bats the best chance of surviving, hopefully until we can either figure out how to get the fungus out of those caves or the vaccine starts to work," Dr. Frick says.
The Michigan Department of Natural Resources, particularly through the work of John DePue in Houghton, has played a crucial role in protecting remaining bat colonies in abandoned mines while facilitating ongoing research.
Researching Bats in the Apostle Islands
NPLSF has been supporting bat monitoring at Lake Superior National Parks. With equipment provided by NPLSF, for example, staff at Apostle Islands National Lakeshore have documented the presence of multiple bat species listed or proposed for listing as endangered, including the Little Brown, Big Brown, Northern Long-Eared, and Tricolor bats.
Data on these bats and their ranges helps park staff plan and implement measures to protect bats during park projects, from historic light station rehabilitations to trail work and hazard tree clearing. Read the full article on bat monitoring here.
How Individuals Can Help
People concerned about bat conservation have several options for positive action. Bat Conservation International promotes a bat gardens program that encourages planting native vegetation to support healthy moth and beetle populations. Advocating for habitat protection and supporting organizations working on riparian and forest restoration also benefits local bat populations.
Perhaps most importantly, increased public awareness and appreciation for bats can drive broader conservation efforts. As Lake Superior’s ecosystems continue facing unprecedented pressures, understanding the interconnected roles of species like bats becomes ever more critical. These small mammals, once taken for granted as summer companions, prove essential to maintaining ecological balance and agricultural productivity across the Great Lakes region.
Helpful Links
Bat Conservation International - batcon.org
The Invisible Mammal Film - doclands.com/film/the-invisible-mammal
Connect With Us:
Lake Superior Podcast Page – https://nplsf.org/podcast
Sign up for the NPLSF e-newsletter – https://www.nplsf.org/subscribe
Find us on Facebook – https://www.facebook.com/NationalParksOfLakeSuperiorFoundation
###
About The Lake Superior Podcast and NPLSF
The Lake Superior Podcast is produced by the National Parks of Lake Superior Foundation (NPLSF), the official nonprofit friends group for Lake Superior’s five national parks: Apostle Islands National Lakeshore, Grand Portage National Monument, Isle Royale National Park, Keweenaw National Historical Park, and Pictured Rocks National Lakeshore.
Funded by grants and private donations, NPLSF projects help preserve, interpret, and celebrate the parks and stories surrounding the Great Lakes’ greatest waters.
For more information or to support our work, contact us at info@nplsf.org.