IRNR researchers survey bat populations in Texas, anticipating white-nose syndrome

First documented in bats in New York state in 2006, white-nose syndrome (WNS) has steadily spread throughout the eastern half of the country and is expected to arrive in Texas in the near future.

WNS is a deadly fungal disease affecting hibernating bats and has been confirmed in 29 states, five Canadian provinces and, in one lone case, as far west as Washington state. Since January, researchers from the Texas A&M Institute of Renewable Natural Resources (IRNR) Bat and Hibernacula Project have been surveying sites across Texas to monitor winter bats and roosts and assess hibernacula, or hibernating environments, prior to the probable arrival of WNS. The project has received help from the Bat Conservation International (BCI) and is funded by the Texas Parks and Wildlife Department (TPWD).

“So far WNS has spread as close to Texas as Oklahoma, so we want to make sure we have baseline data,” said Melissa Meierhofer, IRNR research associate. “We want to know where the bats and hibernacula are prior to when the fungus comes here, so we can continuously monitor them.”

The disease is caused by the cold-loving fungus Pseudogymnoascus destructans, which covers the wings, muzzles and ear membranes of hibernating bat species. Bats with WNS become agitated and are frequently awakened during their critical hibernation period, thus burning fat reserves faster than during normal hibernation and eventually dying, she said.

“We’re worried that some of these bats that were once known everywhere in North America, such as the little brown bat, are going to go regionally extinct,” she said. “What was once the most common bat in the United States is getting wiped out on the east coast.”

Four of the 33 bat species found in Texas have been affected by WNS in other states, Meierhofer said. However, it is unknown if, and how many, other species could still contract or carry the disease.

Several bat species hibernate in dense clusters inside caves, creating an ideal environment for the fungal spores to travel from a single infected bat to the rest of the population, she said. In some sites, 90 to 100 percent of the bats have been wiped out by the disease.

Dr. George Veni, executive director of the National Cave and Karst Research Institute, said the spread of WNS appears to be following bat flight paths, which often go between caves but have also appeared going to mines. Caves are most commonly found in karst areas, or types of landscapes formed from water slowly dissolving bedrock.

“Major karst areas and caves are generally not present in the Great Plains, forming a barrier to the westward movement of many bat species,” Veni said. “However, Texas’ Edwards Plateau is one of the country’s largest karst areas. Located at the south end of the Great Plains, the Edwards Plateau and other Texas karst areas could provide a westward route for WNS.”

Meierhofer said while WNS can spread westward through Texas karst areas, the perspective that Texas could be the only natural bridge to the west was altered when the bat in Washington state was confirmed with WNS.

“The idea of working to slow down or stop the spread of WNS in Texas is critical, but it is also of interest for biologists to learn more about the WNS-positive site in Washington to understand how WNS made such a drastic jump,” she said.

In Texas, most caves and hibernacula sites are on private land, so establishing and maintaining good relationships with landowners is necessary to accessing sites and surveying bat populations, she said.

“To be able to have that relationship so we can continuously go out and monitor caves on private property not only shows that we respect and value landowners, but that we can bring people together around these issues,” she said.

Landowners who allow the researchers to monitor and survey bats and hibernacula on their land can benefit as well. TPWD requires landowners to meet certain major environmental requirements as part of their land management, and bat surveys are considered a strategy for managing wild animals, Meierhofer said. Meeting a specific number of environmental aspects qualifies landowners for tax reductions.

To help find potential sampling sites, the IRNR team uses a grid created by the North American Bat Monitoring Program (NABat) that selects possible locations for winter bat roosts. The team also finds caves through the Texas Speleological Survey, a nonprofit corporation where recreational and professional cavers document cave data, making note of whether or not they saw a presence of bats, bat skeletons or guano in caves they have accessed, and save the information in a database.

The team has surveyed 19 winter sites and visited a total of 34 sites, including caves, bridges, abandoned buildings and tunnels throughout the state, with help from TPWD, the Texas Cave Management Association, the Texas Department of Transportation and private landowners. The team swabbed and visually assessed more than 100 bats for signs of WNS, Meierhofer said, and all tested negative for fungal spores and appeared healthy.

Maintaining healthy bat populations is critical, particularly for the agriculture industry because certain bat species eat insects that can harm crops, Meierhofer said.

“The destruction of crops without these bats could be pretty big. Bats are worth more than $1 billion to the corn crop industry, for example,” she said. “You’re going to notice an increase in insects and with that could also come an increase in diseases.

“A lot of people are afraid of bats, but bats are really interesting being the only mammal that can fly. It’s terrible to say the fungus killing them is helping them, but the good aspect is it’s making people aware of bats and the importance of having them.”

Landowners who have a cave they want to volunteer for surveys can email Meierhofer. Citizens interested in reporting bat sightings in Texas to aid the NABat and help monitor potential population shifts can visit the Bats in Texas observation page.

For more information about the IRNR project, visit its Facebook page.  

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