Fredericksburg Standard-Radio Post

Bat populations are declining rapidly across North America from White Nose Syndrome (WNS). Although the Mexican free-tailed bats are not suffering from the disease, Cave myotis bats have decreased in population by 75% since the fungus was first detected in Texas Panhandle bat habitats in 2017, according to both Bat Conservation International (BCI) and the Texas Parks and Wildlife Department (TPWD).

Planting bat-friendly night gardens and taking precautions when caving can lessen the spread and help bats fight off the fungus.

Brought to the U.S. in 2006, the disease began to spread more rapidly in late 2019. The first large migration of the causative fungus — referred to as Pd — in North America was in 2018, from Appalachia to Washington State, indicating that humans may have acted as a vector. TPWD Bat Biologist Nathan Fuller stated WNS continues to spread about 200 kilometers per year.

This pathogen is “on record, one of the most devastating wildlife diseases,” he said.

The White Nose Syndrome Response Team has identified Cave myotis with both the fungus and infection in states including Texas, Arizona, California, New Mexico and Oklahoma.

In the Hill Country, the Cave myotis bats have tested positive for Pd and WNS and are at risk of endangerment.

“It was a bit surprising that the Cave myotis was hit so hard,” Amanda Adams, Ph.D., Director of Research Coordination at BCI, said. “We are really concerned that the population is declining so rapidly that the [Cave myotis] bats are going to need special protections.”

After visiting maternity roosts to count bats, researchers at TPWD found that the bat population declined from about 18,000 to between 1,500 and 1,200 in the past three years in Government Canyon State Natural Area, north of San Antonio. The TPWD team will soon survey more bat roosts outside of Killeen, and continue to surveil Old Tunnel State Park in Fredericksburg.

The three million Mexican free-tailed bats and between 1,000-3,000 Cave myotis bats at Old Tunnel have not tested positive for the infection but did first test positive for Pd a few years back. (As of May 7, the bats emerged at Old Tunnel State Park. According to the park, the bats were later in emerging because of recent heavy rains.)

White Nose Syndrome fungus thrives in dark, wet, cold environments, infesting bat habitats between 15 and 17° C. The fungus first infects the cave, then the bats as they come in contact with it. A multi-host disease, when various species of bats habit the same location, they are all susceptible.

When the fungus infects the bats, it kills their exposed skin cells, causing them to become dehydrated and wake from their hibernation. This causes them to use more fat stores, leaving them unable to survive winter.

Research studies done by BCI and TPWD have shown that Little brown bats have shown to have adapted to the fungus and are able to make it through the winter, Adams said. There is not yet a conclusion as to why Mexican free-tailed bats appear to not suffer with the disease, even when testing positive with the pathogen, per research by BCI and TPWD.

Intervention and treatment

While bats can recover from WNS, their lifespan is typically shortened, Fuller said. Although research and prevention efforts continue, sprays and vaccines have not yet successfully cured the animals from disease.

Fuller said, “Nothing has shown that it is not viable.” He continued, “our concern must be targeted.”

While spraying caves has shown some success, the process wipes out entire ecosystems. Adams noted that there is collaboration with the National Wildlife Health Center and TPWD to continue to work on different interventions and treatment.

“Even though you can’t see it, that doesn’t mean it’s not there,” Adams said of the fungus.

Both Adams and TPWD still urge taking protections when caving. This includes boiling caving gear, washing clothing and utilizing boot dip stations to kill fungus from the bottom of shoes. Although this may prevent some spread, Fuller stated that most of the contagion is from bat interaction and sharing caves with other infected colonies.

But, he said, “it would be a tragedy to wash our hands and say they have nothing to do with us … If something in the ecosystem is off, it sends a signal that something is wrong.”

Planting bat gardens

Bats eat an estimated $3.7 billion worth of pest control annually, according to the National Parks Service. The Old Tunnel colony, alone, devours over 25 tons of moths per night during nesting season, TPWD found.

Restoring habitats around the hibernacula with plants that support healthy insect populations, like night flowering plants that attract moths, helps the bats. Little brown bats are taking advantage of these artificial prey packages, but research is still being conducted concerning the Cave myotis response to this, Adams said.

To help the bats, Adams advised people plant bat gardens for insects to congregate in one area for bats to quickly eat, “so they’re spending less energy hunting and more energy can go toward building up their fat reserves.”

Native plants and white flowers, which are more likely to be night blooming, attract bats, she said. The Lady Bird Johnson Wildflower Center in Austin has a list of native plants to help bats and other threatened or endangered species in Texas.

“If you’re already planting a pollinator garden, think of the bats, too,” Adams said.