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White-Nose Syndrome Continues to Kill Bat Populations Across North America

Efforts to get the most threatened bat species listed as endangered fail

Near the border of New Jersey and New York, a small bat tucked in its wings and hung from the eave of a forest cabin. The mammal was taking a well-deserved rest during the daylight hours, awaiting the sun’s dip below the horizon in order to hunt the plentiful insects that nighttime promises. These animals, sometimes instilling fear and reminders of Bram Stoker’s creation, are dying in record numbers across the United States. This little bat, barely the size of a baseball, was hanging upside down and simultaneously hanging on for its species’ survival.

close up of hands holding a bat with it's wing stretched outPhoto courtesy of Florida Fish and WildlifeA Florida Fish and Wildlife biologist inspects a bat for WNS. Recent research shows that the fungal disease has caused extensive local extinctions of bat populations.

The fungal disease known as white-nose syndrome (WNS) has been wreaking havoc in the United States for almost a decade, ever since it was “accidentally transported here by humans” from Eurasia, according to Bat Conservation International’s official website. Currently, WNS can be found in 26 states and five Canadian provinces. Three other states have confirmed evidence of the fungus, known as Pseudogymnoascus destructans. The exact number of dead bats is unknown, but thousands became millions some time ago.

“We’re still learning an awful lot about the fungus and the disease, and how it may manifest itself differently in different species,” said Katie Gillies, director of the U.S./Canada Imperiled Species Program for Bat Conservation International. “So we are seeing very significant declines in some species, particularly the northern long-eared bat, the little brown bat and the tri-colored bat. And we’re seeing more variable declines but differences in how the disease impacts species … like the Indiana bat and the big brown bat.”

Gillies called Pseudogymnoascus destructans a cave-loving fungus that needs cold, moist environments to grow. Caves in the Northeast are perfect locations; however, WNS is so pervasive that it has dipped as far south as Alabama and Mississippi and as far west as Oklahoma.

Bat Conservation International describes the fungus as being able to invade the skin of the bats. Both their hydration and hibernation cycles are disrupted, and eventually they produce the characteristic white marks on the face and wings that give the disease its namesake. When a bat wakes up from hibernation in winter, the animal uses up its stored fat reserves. They fly around and then “usually freeze or starve to death,” BCI reports on its website.

The efforts to stop WNS have brought together researchers and bat advocates in an unprecedented effort to figure out what’s going on and how to stop the fatalities. “You’d think it’d be very simple, but bats are cryptic, and small, and they move around a lot,” Gillies said. “We don’t really have a really good way of estimating bat populations. One of the best ways we have is to go into these hibernation sites and count the bats that are on the wall. So that’s a very imperfect system because bats move around a lot. There’s a lot of human error. Some are really difficult to see, but it’s frankly the best that we’ve got, right. … Maybe they go in after white-nose has been confirmed there, and one to three years afterward is when you generally see that giant population crash. So they go in, and maybe they see dead bats on the ground. But mostly they just don’t see any bats there at all.”

In 2012, when I last reported on WNS for Earth Island Journal, Justin Boyles, then a post-doctoral researcher at the University of Tennessee, said that the bats die, fall to the ground and turn into “this rotten goo.”

“The fungus actually like permeates into their dermal layer and essentially liquefies at the cellular level,” Gillies explained. “This is really problematic because bats use their wings and ears to help them thermo-regulate throughout the winter and to help them manage their hydration levels throughout hibernation. … Bats will wake up through the course of the winter anyway to void their system, to get a drink, to move to another part of the cave that’s more conducive to what they’re looking for. So they can wake up and then move around, but they only have so much fat and can only wake up so many times before it becomes very detrimental.”

The Bat Attack

Dr. Allen Kurta, chair of the North American Society for Bat Research’s Board of Directors, didn’t mince words when describing the WNS problem.

“Well, I mean we’re in the middle of an epidemic in North America,” he said. “So this thing started 2006-2007, and it’s still marching across the country. So, yes, it’s still a huge problem, but we’re never going to get rid of it. We’re just going to have to live with it. There’s no way that you can eliminate this fungus from the environment.”

Researchers have developed ideas on how to minimize the spread of the fungus, such as decontaminating clothes after visiting a cave, said Kurta, who is a professor at Eastern Michigan University. However, even if visitors to caves decontaminate their clothing, the chief mode of transmission is from bats to the environment to more bats. “The bats are the ones that are spreading most of this disease, so in terms of containing it, I don’t think that there is a way to contain per se,” he said.

Kurta, who studies the ecology, behavior and natural history of mammals with a particular interest in bats, said that the high number of fatalities is accurate. “Those are very real numbers from the Northeast and from the Mid-Atlantic states,” he said. “They’ve had the disease for the longest period of time, and so they’ve seen the greatest amount of decreases. I’m in Michigan, and we’re sort of on the leading edge here. We first found it in spring of ’14, I think. So last winter was the first full winter, so we’re just starting to get our mortality going here.”

In the early stages of the infection, when the white growth has not yet occurred, the fungus is present in low levels, so analysis is done by taking swabs of the skin, Kurta said. These swabs are then checked for DNA of the fungus.

To explain the depleted numbers, Kurta referenced recent industry research pointing to the fungus’s presence in Europe and the United States. “I think what we’re getting at is that they [Europe] experienced this epidemic hundreds, thousands of generations ago, and so their populations adjusted over time and are very, very small populations,” he said. “So we are not seeing mass mortality in Europe now, but there’s a good chance that that mass mortality occurred a long time ago.”

a little brown bat with white-nose syndromePhoto by Jonathan Mays, Wildlife Biologist, Maine Department of Inland Fisheries and WildlifeA little brown bat with visible symptoms of white-nose syndrome.

The research paper, published earlier this year in Global Ecology and Biogeography, found that WNS “has caused a 10-fold decrease in the abundance of bats at hibernacula in North America, eliminating large differences in species abundance patterns that existed between Europe and North America prior to disease emergence.” The fungal disease has also caused “extensive local extinctions.”

In the eastern US, there were populations that Kurta predicted had up to 300,000 of these flying mammals. “In Europe, 300 is a large number,” he said. “So we’re getting knocked down to what’s typical for Europe, and we probably will lose species along the way.”

Because WNS is a cold-loving fungus, there is no fear of it spreading to humans or birds. Kurta said it would also not affect nectar-feeding, blood-feeding, meat-eating, fish-eating or fruit-eating bats in countries with warmer climates in Central and South America. “It’s not going to grow on a typical mammal or a bird that is active all of the time because the skin of those animals is much too warm,” Kurta said. “But certain animals though are going to go into hibernation. And I’m curious as to whether or not [those] animals, mammals other than bats, are going to be susceptible to this fungus because when you go into hibernation, then you lower your body temperature down within the range that is desirable for the fungus.”

Because bats are long-lived mammals that typically produce one offspring per year, it will take generations to rebuild populations. “When you get a calamity like this occurring, it will take a population a very long period of time to recover when you’re only pumping out one offspring per year,” Kurta said.

A Species on the Brink

Mollie Matteson is a senior scientist for the Center for Biological Diversity, which advocates for greater protection of bats. WNS takes up much time in her schedule, and she focuses on those species — including the northern long-eared bat — that are facing difficult, uphill battles.

The Center for Biological Diversity has petitioned for the Endangered Species Act listing of the northern long-eared bat. Originally, the US Fish & Wildlife Service proposed listing the bat as endangered; however, the species is currently listed as only “threatened.”

Here’s how the USFWS explains the change in status on its website: “In simple terms, endangered species are at the brink of extinction now; threatened species are likely to be at the brink in the foreseeable future. Therefore, the definition of each term hinges on the time element, now versus the future. After we proposed listing the northern long-eared bat, we looked more critically at how the definitions of threatened and endangered fit within the context of the northern long-eared bat and the spread of WNS.  We determined that the bat is not endangered at this time because WNS has not yet spread throughout its range and will not likely affect its entire range [for] some years.”

Matteson alleges that politics were at play, with the USFWS receiving pressure to change its original plans. “There’s been a whole series of events that have happened since then [proposal for endangered status], a lot of pushback and political pressure from industries and from politicians that are not as much interested in environmental protection as they are in the continuing to support the interests of industry,” she said. “And so that led eventually to the Fish & Wildlife Service backpedaling on its recommendation to list as endangered, and they ended up listing the species this April as threatened, which is a less protected status.”

The USFWS also passed an interim rule that exempted activities such as forest management practices, maintenance and limited expansion of transportation and utilities rights-of-way, prairie habitat management, and limited tree removal projects, provided these activities didn’t harm known bat roosts and hibernacula.

The political struggle seemed to focus on the habitat of the northern long-eared bat, which is found in mature forests. “They seemed to be pretty keyed into using roost trees that are larger, older, and so as you can see that need of theirs for habitat could come up against forest management and logging essentially,” Matteson said. “So the timber industry in particular has been very vocal and very vehement.”

The Hardwood Federation, which represents thousands of hardwood businesses in the US, and according to its official website, acts “as the industry’s advocacy voice on Capitol Hill,” is one of the groups opposed to the ESA listing. At the time of the northern long-eared bats’ possible inclusion on the ESA list, the federation claimed on its website that: “If the restrictions currently included in the interim guidance become final and are enforced, they would have a devastating effect on forest management, forest landowners, and the entire forest products value chain.” It claimed that the best solution would be to “find a cure for WNS” to preserve both the bats and the communities that rely on the forest for their livelihood.

“Many of these big industries, they simply don’t want to feel any restriction in terms of carrying out their business,” Matteson said. “And if there are northern long-eared bats in their area, they might [have] some degree of limitation on what they could do in order to protect the bat.”

A common question Matteson receives is why should people care about the future of bats in North America. She points to their unique role as nighttime predators that keep insect populations in check. However, she was broader with her plea for understanding.

“As part of the web of life, they have a place,” she said. “If you value life, and if you value the natural world, then bats are part of that.”

As stakeholders debate the fragile future of bats in North America, the summer nighttime skies, once home to so many flying specks of black, have grown silent in many places. “It’s definitely much worse than it was five years ago,” Matteson said. “The projections are all that this disease will continue to spread throughout the continental US.”

John Soltes
John Soltes has written previously for Earth Island Journal on a number of species.

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