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A deadly fungus is sending Iowa bats spiraling. Researchers are studying their downfall
Central College professor finds that in some cases, certain bat populations have declined 85 to 90 percent
Aug. 4, 2023 5:00 am, Updated: Jan. 26, 2024 3:35 pm
This is the fourth installment of Nature’s Alarm, a series about endangered and threatened species and research in Iowa.
Night had fallen hours ago over an oak hickory forest in the Big Hollow Recreation Area near Sperry in southeast Iowa. Dots of starlight peeked through the trees, branches and leaves silhouetted above.
Sound cocooned the forest — birds, frogs and insects calling out to each other in the night. Lightning bugs began to dot the underbrush. It was the peaceful normalcy of nature.
And then, from the darkness: “We’ve got one!” Headlamps bobbed in excitement in the distance. Their attention was on a tiny creature tangled in the net in front of them.
Russ Benedict, a biology professor at Central College, raced over to his summer research students to inspect the mess of delicate strings and wings. One glance was all it took to confirm the first mammalian catch of the night: an eastern red bat.
Short rust-colored fur coated its small, wiggling body complete with strong chest and shoulder muscles. Its stomach caved in, a sign that it hadn’t found food yet. Thin brown skin webbed across its wings. A series of high-pitched chirps — distress calls — flowed from its open mouth.
Like most bat species, populations of eastern red bats are declining across the state. Any data about them is important. But it wasn’t one of the target species Benedict hoped to catch that night.
Benedict is the only researcher in Iowa who catches bats to study them. Big Hollow Recreation Area is one of 10 locations he’s surveying for endangered or soon-to-be-listed species across southeast and north-central Iowa.
His results are quantifying some of the most dramatic population declines in the country — mostly due to one damaging invasive species.
Downfall by fungus
Bats are important predators of night-flying insects. They’re estimated to contribute $1 billion worth of pest control each year for cornfields alone. Worldwide, their annual impact is close to $50 billion, Benedict said.
The nocturnal creatures catch their prey using echolocation. They emit ultrasonic sound waves that surpass the bounds of human hearing, which bounce off the bat’s surroundings, return to their ears and tell them where their next meal is.
In the winter, many of Iowa’s bat populations hibernate in caves or mines. Some rest in attics or barns. Others migrate to other countries in search of warmth.
Nine species of bats currently roam Iowa skies. Two of them are federally endangered: the northern long-eared bat, listed this past November, and the Indiana bat, listed in the 1960s. About three years ago, both species started to vanish in Iowa, Benedict said.
The leading theory for decline of Indiana bats is its diet of insects that have been exposed to pesticides. Northern long-eared bats, on the other hand, have a clear and defined threat: an invasive species called white-nose fungus.
The fungus is native to Europe. Around the late 1990s, cave explorers likely brought fungus spores to the U.S. on their shoes or equipment.
“It's kind of your classic invasive species (story), where humans accidentally brought something causing disease to a new area, and then the new species it's encountering have no immunity to it,” Benedict said.
The fungus attacks any exposed skin on bats. As it grows, it itches — so much so that it repeatedly wakes up infected bats when they’re supposed to be hibernating. They burn through their energy and can starve or get dehydrated before spring comes. Mortality rates for infected bats of sensitive species can range from 80 percent to 100 percent.
White-nose syndrome was first documented in New York in 2006. It has since spread across the U.S., killing more than 90 percent of northern long-eared bats, little brown bats and tricolored bats in fewer than 10 years, according to a 2021 study.
The fungus was first confirmed in Iowa bats in 2015.
“We may ultimately end up with three or potentially four endangered species in Iowa all because of this fungus,” Benedict said. The U.S. Fish and Wildlife Service proposed to list the tricolored bat as federally endangered in September. The agency is currently reviewing the status of the little brown bat.
Mapping years of data
During the day, the trails at Big Hollow Recreation Area are used for walking. But on warm summer nights, the cleared pathways turn into flight corridors for bats. That’s where Benedict and his research students targeted their research.
They strung 18-foot-long nets across two pathways and hiked them up about 15 feet high. The black nylon mesh was almost invisible, especially at night. If a bat didn’t see it coming — or sense it with echolocation — it tumbled into excess netting that trapped it. Every 10 minutes, the team checked the nets.
This summer marks the second year in a row Benedict has surveyed Iowa bat populations. Each new data point helps him paint a picture of their decline. Although he’s specifically focused on list or soon-to-be-listed species, he also collects data on other bats captured in his nets — which all goes back to the Iowa Department of Natural Resources.
He crafted his survey schedule based on historic Iowa hot spots of the target species before white-nose syndrome rocked their populations. Benedict uncovered that through previous studies within the last 12 years. Now, he’s replicating the same methods at the same locations on similar dates to map population health throughout the years.
“The first time we netted those spots before white-nose fungus was out, we probably caught 70 or 80 northern long-eared bats in those 10 nights,” Benedict said. “We caught three or four last year.”
Once a bat is successfully untangled from the nets, Benedict measures its forearms to confirm their species. He checks its wings for scarring — which could indicate exposure to white-nose fungus. He also notes its gender and reproductive status. If it’s an endangered species, he photographs, weighs and bands it for the FWS.
Finally, he dabs a small dash of bright pink powder on them — a reminder they’ve already crossed paths that night. The bat is then released back into the wild.
“A lot of research, in a sense, has a little element of Christmas Day to it,” Benedict said. “What's going to be inside this package when we open it up? It's definitely exciting.”
Dire and depressing decline
Benedict’s original surveys of the Big Hollow Recreation Area occurred in July 2011, after a nearby dam was constructed. He caught 25 bats, including three Indiana bats and three northern long-eared bats.
This summer, he caught seven bats at the location. None of them were his target species.
“This is playing out exactly the way last year did,” Benedict said. “Just complete collapses in these populations.”
The 2023 summer surveys, which finished last week, were similar to last year’s results:
- Northern long-eared bats declined 94 percent compared to the original surveys.
- Indiana bats declined 88 percent.
- Little brown bats declined 86 percent.
There's always an element of variability from one night to the next, so capture data isn’t wholly representative of bat population `numbers, Benedict said. But the magnitude of the declines shows significance.
“If we only found they declined 5 percent, then we’d probably say that was variation,” he said. “But the fact that it was 80 to 90 percent … that's not just variation.”
There’s no easy cure for white-nose fungus. Even if there were, it would be hard to scale treatment up to all U.S. bat populations.
Emerging research has found cave bacteria that dramatically reduces the impact of the fungus at high populations. And some bats have survived white-nosed fungus and created babies that were immune to it.
Even so, bats reproduce really slowly. A female will have one baby per year.
“I will never see populations of these bats increase in my lifetime,” Benedict said. “It'll possibly be 100 to 300 years to get their numbers back to where they once were.”
Benedict has been catching bats for about 36 years. He loves the creatures — so much so that, when he caught his first northern long-eared bat of the year last year, he started crying.
“Here I am, at midnight out in the woods, and I'm choking back tears because I knew we should have caught 80 of these guys. And here's the first one,” he said.
“I've been working on bats for a long time now. To go out to places where you've caught lots of them before and then to not catch them — that wears on you. It hurts.”
What can you do?
Bat boxes are a popular yard item. But they only help big brown bats, Benedict said, which can adapt to a variety of habitats. Their populations are common and holding steady.
What can help declining bat species? Talking to local officials to increase funding for research, habitat conservation and species protection, Benedict said. You can also get involved with nonprofit organizations that support bat populations.
How we reported this series
Nature’s Alarm started as a question this spring: On the 50th anniversary of the Endangered Species Act, what do we know about threatened and endangered species in Iowa? Can we highlight some of these species and the researchers studying them?
Members of The Gazette’s newsroom have spent the last four months planning and reporting this series, which began July 16 and has been publishing weekly.
Reporter Brittney J. Miller started with background interviews in search of active research occurring for at-risk species in Iowa. Once she identified target species — each representing a different fauna group — she coordinated with researchers to accompany them into the field with photojournalist Jim Slosiarek and social video producer Bailey Cichon. Digital editor John McGlothlen built graphics to accompany the stories online.
The Gazette team clambered through vegetation in search of bumblebees, worked by the light of headlamps to spot bats, and floated along rivers to catch a glimpse of fish, amphibians and mussels to report this series.
Brittney J. Miller is the Energy & Environment Reporter for The Gazette and a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.
Comments: (319) 398-8370; brittney.miller@thegazette.com
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