The Detrimental Effects of White-Nose Syndrome on Native Texas Bats

Texas State researchers begin to study the effects of lethal white-nose syndrome on native bats, and how to combat it

It’s been over 10 years since a silent killer started taking down America’s bat population, but scientists are still stumped by the deaths. Today, the disease has finally made its way to Texas, where it threatens the iconic local bats.

Texas State researchers studying white-nose syndrome, a deadly threat to native bats in central Texas, share the potential devastating effects of the disease on local bat populations and their surrounding ecosystems.

White-nose syndrome (WNS) is a fungal disease that is responsible for large die-offs in several bat populations across North America.

The syndrome is caused by a fungus, Pseudogymnoascus destructans (Pd), that lives in the environments of many other continents such as Europe and Asia but hasn’t had any negative effects on bat populations there as it has had with bat populations here in the United States and North America in general.

The negative effects of this fungus on American bats was initially detected in 2007 in the northeastern United States when biologists began to notice whiteness around the noses, and mouths of bats in the area, thus the name white-nose syndrome.

They also began to note an abnormal increase in the number of dead bats with these white noses. The bats were being found during a time when there should have been a decreased amount of bat visibility as they would have usually been hibernating.

Since then, the fungus has traveled down and has made its way to Texas where researches have begun to study the effects that the syndrome has had on native bat populations but have been met with many difficulties.

“Bats are really hard to research. They fly, and they have really large home ranges.”said Sarah Fritts, a biology professor at Texas State University. Fritts has been researching bats with the syndrome and the different ways to combat the negative ecological effects.

“It just hit us in 2007 so there hasn’t been a lot of time for us to get a lot of research done about how it’s affecting bats, what the mechanisms are or what species it affects more.” Fritts said. “However, we do know that it’s not the actual fungus itself that kills them. What the fungus does is affect the bats’ hibernation. When bats hibernate, they really decrease all bodily functions. They don’t eat or drink as much because of this, and when they get white nose syndrome, it wakes them up consistently and it wakes them up during a time when there’s not much food to eat or water to drink, so they slowly deplete their fat reserves and basically starve to death.”

The fungus that causes WNS was detected in many caves that bats inhabit in Texas for the first time in 2017, causing the researchers to worry about the local bat populations.

“We knew then that it was probably going to start affecting our bats.” Fritts said. “There’s usually a lag time of a couple of years between the time we first see the fungus and when it starts affecting the bats so it’s really just a waiting game for us and after this winter, we think it might spread to other species.”

In terms of what species are at risk of contracting the fungus and WNS here in Texas, researchers have observed that any bat population that hibernates in a cave afflicted by the fungus or that comes into contact with another bat that already has the fungus is susceptible.

“We do know that it can travel bat to bat, and bats are very social animals. We have some caves here in central Texas with about 20 million bats in them.” Fritts said. “There are lots of different bat species here one of the most beloved being the Mexican freetail bat. These bats are big migrators and most of them migrate to Central and South America, but the Cave Myotis is one of the species that does hibernate here in central Texas and that’s the one that we’ve seen the worst effects on so far.”

White-nose syndrome can spell disaster for a bat population. However, complete decimation is not certain.

“There are some species and populations that have had 99% declines, just die-offs of complete species in some areas, whereas other species, we can swab them with a Q-tip and see they have the fungus on them but they’re not dying or at least not dying at the same rate as other species.” Fritts said.

Elijah Lee, a PhD student studying biology at Texas State that has also been working with bats and WNS for a number of years has observed a situation like this first-hand while working with populations in other states.

“Some species have higher rates of mortality. When I was working in Pennsylvania, we lost about 99% of our little brown bat population.” Lee said. “Whereas, the big brown bat population had a mortality rate of about 15%”

Originally, it was thought that WNS would not be a threat to bat populations in Texas because it was believed that the native bats hibernated differently than those in the north because of the state’s comparatively mild winters.

Nathan Fuller, statewide bat specialist with Texas Parks and Wildlife has been working with White Nose Syndrome for the past 13 years and witnessed a large die-off of bats.

“In Texas, a biological winter really only happens in, say like December to February so we thought that there wasn’t going to be much of an impact on our data, but it turns out we were wrong.” Fuller said. “We had a pretty big die off of animals last year, so almost 20 counties in Central Texas reported dead Cave Myotis bats. People were finding them in their front yards on their mailboxes and trees, things like that, during a time where there really aren’t that many out there.”

To combat this, and help conserve the bat populations, several projects are underway.

“We’re trying to do a lot here at Texas State to research the threats the bats are facing and how they interact so we can help the bats the best we can.” Fritts said. “One of the things we’re doing is monitoring it statewide, acoustically, by deploying acoustic detectors that pick up the bats’ echolocation calls.”

Because bats have the unique ability to sense their environment through echolocation calls and because each species has a slightly different call, scientists can use microphones and detectors to track their movements and distributions across the state.

“We’re just now deploying the acoustic detectors, so we don’t have data from this yet and we’re working on this project very closely with Texas Parks and Wildlife as they are the ones who are funding the project.” Fritts said. “When we do this for the next years, we can start getting accurate tracking and we will be able to finally see how white nose syndrome may be affecting the populations here.”

Along with this, there have been efforts to fight WNS through more direct ways.

“There have been a few attempts at cleaning the caves of the fungus while the bats aren’t hibernating as well as people trying to use fungi or other microbes that already exist in the caves, but one of the big challenges is that cave habitats are really delicate, so you don’t want to introduce something that’s going to take over the system.” Lee said. “The problem with that is, we know so little about where these hibernacula are. Some bats hibernate in places we don’t even know about so you may be able to scrub one cave clean or take care of one bat population, but they’re going to disperse over the landscape, interact with other bats and probably bring it right back.”

Because of this, Lee believes that acoustic monitoring is the better option for combating the syndrome.

“Efforts are better spent on monitoring and protecting what we have.” Lee said.

Despite the many efforts to help bats overcome WNS, because so little is known about the syndrome and the hibernation places of many bat populations, it becomes almost impossible to prevent the bats from succumbing to the syndrome.

“In some cases, you just have to sit back and let natural selection occur. This is called evolutionary rescue. You have some animals that are resistant to disease in some capacity, and those are the ones that will survive and go on to breed.” Fuller said. “The problem is that the population decline in bat populations that are hit by white-nose syndrome are so intense that evolution doesn’t always have the time to catch up. Evolutionary rescue doesn’t work if there are too many that are dead, which is why our goal is to create some breathing room and prevent massive declines from happening so that the natural processes of natural selection or evolutionary rescue can take place.”

The negative ecological impact that WNS has could have a lasting impact on the environment and on other species as well.

“Bats eat of a lot of things like insects and other pests, but a lot of animals also eat them.” Fritts said “Predator animals like owls snakes and hawks eat them, so if we lose bats, we could lose this really important part of the ecosystem for other vertebrates as well.”

Bats also play an extremely important role in humans’ day to day life as well, especially in the agricultural sphere.

“Bats are extremely beneficial in a number of ways. They eat insects and can be very useful for agriculture by reducing the amount of pesticides they have to use on crops. They are even estimated to have saved between $30 and $300 billion dollars for farmers.” Lee said.

Bats are also pollinating animals for many of the plants that we use to create things for human consumption.

“If you’ve ever had a bottle of Tequila, you should know that bats are very important pollinators for a lot of plants including the agave plant.” Fritts said.

White-nose syndrome is believed to have been introduced to the ecosystem by cavers who didn’t realize that their simple actions of not properly disinfecting themselves would accidentally introduce the fungus to the hibernating bats.

“We have to be careful as humans because the fungus that causes WNS can get on our shoes and it can get on our clothes and so if people go into one cave and want to go into another, they really have to disinfect themselves.” Said Fritts.

This is not the only problem that humans have caused for bats.

“Here in Texas, wind turbines are a great threat to bats.” Said Fritts “Bats are getting decimated by them, which has been causing a lot of issues in the past couple years. Add on top of that climate change, human population growth, and of course white-nose syndrome, it’s really starting to affect our bats”

The researchers believe that being informed about the situation at hand and donating money to conservation organizations such as the Wildlife Conservation Society and Bat Conservation International, are some of the best things the general public can do because those organizations fund research that can really have a positive impact on the bat populations.

“I ask people to be vigilant.” Fuller said. “Be aware of what’s around you and be willing to be a steward of your area so that we don’t lose our bats.”