Biennial bat count shows continuing losses to WNS

This unfortunate Little Brown Bat is afflicted with WNS. The fungus can be seen growing on the bat's muzzle. The fungus irritates bats and causes them to become active in winter, when they should be hibernating. The activity and lack of food cause affected bats to die of starvation. Photo courtesy West Virginia DNR.
This unfortunate Little Brown Bat is afflicted with WNS. The fungus can be seen growing on the bat’s muzzle. The fungus irritates bats and causes them to become active in winter, when they should be hibernating. The activity and lack of food cause affected bats to die of starvation. Photo courtesy West Virginia DNR.

Due to their gnarly appearance, bats invoke a sense of horror in many people. But the small flying mammals are one of man’s best animal friends. By eating huge amounts of insects, bats are an enormous benefit to agriculture and also help us to enjoy the great outdoors.

In 2009, a deadly bat disease called white-nose syndrome (WNS), arrived in West Virginia. WNS is a disease affecting hibernating bats, named for the white fungus that appears on the muzzle and other parts of the bat. Bats with the fungus become active in winter, when they would normally be hibernating. The bats lose fat reserves and leave their hibernaculum in search of food, when none is present. Affected bats eventually die of starvation.

This winter, the West Virginia Division of Natural Resources (DNR) completed a biennial bat count in several caves in Randolph, Tucker, Pendleton, Grant, Monroe, Greenbrier, Mercer, and Pocahontas counties. The count revealed that five West Virginia bat species have been ravaged by WNS, while two species seem largely unaffected. A bat expert described the situation as “grim.”

DNR biologist Craig Stihler supervised the bat count.

A cluster of Indiana bats observed during this winter’s bat count. Prior to the arrival of White-nose syndrome, the greatly endangered species was making a strong comeback in West Virginia, thanks to the efforts of DNR biologist Craig Stihler. But the species is once again on the brink of survival due to the scourge of WNS. Photo courtesy West Virginia DNR.

“Typically, we do our surveys every other winter,” said Stihler. “We try to minimize disturbance to the bats. We know that when we go in a cave, we disturb them, they wake up and they use up fat that they would normally use for hibernation. So, we go in once every other year to minimize the disturbance.”

Stihler said the DNR has conducted bat counts since the 1980s, when two species were listed as endangered.

“In West Virginia, we’re fortunate to have a good history of bat surveys,” he said. “We have some baseline information from before white-nose syndrome showed up, so we know what’s going on.”

WNS was first observed in the United States in the winter of 2006-2007 in New York state.

“At that point, nobody realized how bad it was,” said Stihler. “The following year, they realized it was no fluke, it was there and it was back and it was devastating the bats.”

Three years later, WNS was first observed in West Virginia in a Pendleton County cave. Since then, the effects of the disease have been catastrophic.

“We have 20 caves that we counted this past winter,” said Stihler. “Little brown bats were probably our most common cave bat before white-nose. It was by far the most abundant bat we saw. In all of our caves combined, we’ve lost 97.4 percent of those.”

Prior to the arrival of WNS, Stihler led a successful program to restore populations of the endangered Indiana bat. As a result of that program, the population of Indiana bats in Hell Hole Cave in Pendleton County had increased from 3,300 to more than 18,000.

“We’ve lost 84.5 percent of the Indiana bats,” said Stihler. “Even though they were doing very well as a result of our protection efforts, up until that time, it was no match for the fungus that was coming in.”

A Virginia Big-eared bat.
A Virginia Big-eared bat.

The tri-colored bat got its name from the distinct tri-coloration of each hair, which is black at the base, yellow in the middle and brown at the tips. One of the smallest bats in North America, the tri-colored is suffering greatly from the ravages of WNS.

“Another species that was hit hard is the tri-colored bat, that used to be known as the Eastern Pipistrel,” said Stihler. “It’s one of our smallest bats and it’s really widespread. It’s a bat that’s probably found in more caves than any other species, although usually not in really large numbers. We’ve lost 94.5 percent of them.”

Big brown bats are very hardy and can survive where other bats cannot. They have brown to copper-colored fur on their back with the belly fur being lighter. They are found in almost all habitats from deserts, meadows, cities, to forests, mountains and chaparral. The recent count shows that big browns have declined by 39 percent.

The northern long-eared bat is a small bat associated with mature, interior forest environments. Unlike most other bats, the northern long-eared forages along wooded hillsides and ridgelines. This winter’s bat count showed a decline of 56 percent in the population of northern long-eared bats.

Two bat species – the Virginia big-eared and the Small-footed – seem to be resistant to WNS. The Virginia big-eared population has increased by 92 percent since 2005 and the Small-footed has increased by 10.5 percent. But those numbers do not come close to making up for losses of other species.

New York, the first location in North America to experience WNS, might have seen the worst of the bat disease. Recent surveys there showed slight increases in bat populations – that had been nearly annihilated by WNS.

Based on the reports from New York, Stihler was guardedly optimistic prior to this winter’s bat count.

“We were hoping that we had hit bottom and our populations would not decline further,” he said. “Folks in New York are saying that their populations stabilized at a really low level, but they did stabilize and now they’re seeing a slow increase in species like Little Brown bats. We were hoping to see an increase in bats.”

But the West Virginia bat count showed continuing losses.

“This past winter, the sites we looked at, compared to the last survey in 2013, we’re sill seeing a 26 percent decline in little browns, a 26 percent decline in Indiana bats and a 52 percent decline in tri-colored bats,” said Stihler. “So, the BatNumbersChartdecline is slowing down, but we’re not at the bottom yet. I’m optimistic that in 2017, the numbers might be the same or better. But at this point, we can’t say we’re at the bottom. We just don’t know. It’s a pretty grim situation out there.”

Amid the devastation, there is a glimmer of hope that vulnerable bat species can survive and overcome the WNS plague. Some signs indicate that surviving bats might have or be developing resistance to the disease.

“When we first saw white nose in the first couple of years it hit, we would go in a cave and see a lot of bats that were clustered near the entrance of the cave, which is where they normally should not be,” said Stihler. “They were basically staging to leave the cave because they were starving and going out to look for food. The bats had a lot of fungus on them. In some cases, their whole muzzle was covered with fungus and it would also be on their body and wings.

“The bats we’re seeing now tend to be in the spots where they had normally hibernated in the past and you see very little sign of fungus on them. We assisted some researchers by swabbing the body of the bats and sending it off for DNA testing. The bats still had fungus on them, but we’re not seeing the visible fungus like we used to. To the naked eye, they seem to be in better shape, but only time will tell. The question is – is the bat more resistant? It seems to be. It’s encouraging because we don’t see the fungus like we used to see it.”

Since its appearance in the U.S. in 2006, WNS has spread to 25 U.S. states and five eastern Canadian provinces. WNS is not a danger to humans.

Due to the tragic loss of millions of bats to WNS, it has become important to help conserve bats. Bats that mistakenly enter a home should not be killed.

Guidance for dealing with bats that mistakenly fly into your home.
1. Don’t panic. The bat is flying around to find a way out. It is not trying to attack anyone.
2. Turn on the lights so that both you and the bat can navigate around easily.
3. Close any doors that lead to adjoining rooms. Open all doors and windows that lead to the outside.
4. Be patient and, in most cases, the bat will fly back outside within a few minutes.

If the room does not have a direct exit to outside: use a mesh net or towel to gently catch the bat in flight while also wearing thick work gloves. If the bat has landed you may can place a container over the bat, slide a piece of cardboard along the surface, under the container to gently drop the bat into the container and cover the opening as well. Take the bat in the container/net outside. Open the container on its side, in the air or against a tree. Let the bat climb or fly out. Do not leave the container with the bat on the ground, it’s not a safe place for bats and it’s difficult for them to take flight.

Current decontamination protocols for cavers to prevent the spread of WNS can be found at:

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