Central Texas bats take a hit from fatal white-nose syndrome

Central Texas is the battiest region in the country. The area is also one of the most recent threatened by white-nose syndrome, a newly emergent and devastating disease affecting hibernating bats — a disease that could cost the nation’s farmers billions of dollars in pesticides and crop losses. 

Texas is home to 32 of the 47 species of bats in the United States, including the world’s largest population, which lives in Bracken Cave near San Antonio, and the world’s largest urban population, found under the Congress Avenue Bridge in Austin. Those populations of Mexican free-tailed bats are not yet threatened by white-nose syndrome because they migrate, most wintering in Mexico, but they are spreaders of the disease.

White-nose syndrome is named after a white fungus that can be seen on a bat’s muzzle, ears, and wings. It was first found in the United States in upstate New York in 2006 and mostly affects hibernating bats, in particular, cave myotis. The disease causes bats to lose their fat reserves, waking them up and forcing them to leave hibernation in search of food. This usually occurs mid-winter, when food is scarce and conditions are extreme. The bats either die of starvation or from exposure to the elements.

The first bat known to have actually died from WNS in Texas was at Enchanted Rock State Natural Area in Fredericksburg in March 2020.

“Then, the world shut down (because of COVID-19) and hindered what we were able to do,” said Nathan Fuller, bat biologist for the Texas Parks and Wildlife Department. 

Fuller was eventually able to submit 50 more dead bats from 20 counties for testing. The largest portion of those were from Central Texas and most came back positive for the white-nose syndrome pathogen.

In the Highland Lakes, another bat that succumbed to WNS was found at Inks Lake State Park. Dead bats testing positive for the disease were then found at Bamberger Ranch Preserve in Johnson City. 

“Cave myotis populations have taken a big hit,” Fuller said. “There’s a site in Fort Hood that had 35,000 cave myotis. Now, there are actually zero bats there.” 

The cave myotis population at a cavern in Colorado Bend State Park near Lampasas is also in trouble. In the past, it was home to 18,000 to 20,000 bats. Fuller has seen a 70-80 percent decline in summer roosts over the past three to five years. He was afraid the bat population had dropped to zero when he visited the site in July 2023.

“There are about 450 bats left in there, which is excellent,” he said, “but also really heartbreaking to see so many bats are gone. That’s only around 10 percent of the historic population.”

Fuller recently detected white-nose syndrome on a live Mexican free-tailed bat in Bracken Cave. While WNS is not as deadly to migrating bats, the animals are carriers and the reason the disease spreads so rapidly. 

“It is spread by contact and almost exclusively by bats,” Fuller said. “An infected bat rubs up against a surface that has the disease and becomes a carrier. Bats cluster together. They fly 50 kilometers to the north, then 150 to the south. They move it around really well.”

However, the syndrome’s initial introduction to America could have been via people. Fungus spores can cling to clothes and spelunking gear and be moved from cave to cave if gear isn’t properly cleaned between visits. WNS is believed to have found its way to the northeastern United States via travelers from Europe, where the disease has been prevalent for years.

The TPWD and other experts worry about a declining population because of the economic impact of these insectivores. Bats can eat their weight in mosquitoes and crop-damaging moths and beetles every night. Texas bats save farmers more than $1.4 billion each year just in pest control, according to the Texas A&M AgriLife Extension Service.  

“They literally are billion-dollar bats,” said Janet Hurley, a pest management specialist for AgriLife in an online TAMU article. “We have resident bats that never leave, but many species migrate into Texas from Mexico, and some migrate from Mexico up to Wisconsin. Many times, their migration will coincide with the migration of the various moths. They can’t consume enough, but they try.”

Bats are a big draw for tourists, whether cave myotis, which are here year-round, or Mexican free-tailed, like those found under the Congress Avenue Bridge. The Austin bats generate about $10 million a year in tourism revenue, according to Bat Conservation International, which is based in the capital city. 

Bottom line: People love bats, Fuller said.

“Bats are cool,” he continued. “I’ve spent my entire life working on bats. I like to remind people there’s intrinsic value in organisms like bats. They are the only flying mammal. They have really cool behaviors and cute faces. They are wonderful little creatures. If we lose them, we lose a cool part of the ecosystem.”

Humans really can’t do much to save bats from white-nose syndrome except educate fellow Earthlings about their cool cousins with wings, Fuller said. You can also protect bat habitats and provide water.

“They like to drink right after they come out for flight,” he said. 

Installing bat boxes is not really helpful because the most common boxes are either too hot or too cold and the bats don’t like them.

“Email me if you want a plan for a really good bat box,” Fuller said. His email is nathan.fuller@tpwd.texas.gov. 

You can also report any large-scale bat mortalities to the Texas Parks and Wildlife Department, especially those that occur during the winter. If you see dead or dying bats, call the TPWD’s 24-hour Communication Center at 512-389-4848.

BATTY DATA

Most cave myotis bats hibernate over the winter, while Mexican free-tailed bats migrate. Here are some other differences, and similarities.

CAVE MYOTIS

• normally roosts in caves in the thousands
• most stay in caves year-round
• leaves each night after the Mexican free-tailed bats
• can fly about 60 miles round trip in a night
• are slower but stronger flyers than Mexican free-tailed bats

MEXICAN FREE-TAILED BATS 

• most common bat found in Texas
• was named the state flying mammal in 1995
• known to roost in the millions
• migrates to Texas from Mexico in February
• returns to Mexico with the first fall cold front
• can fly up to 100 miles round trip in a night
• can fly up to 60 mph with a tailwind

BOTH

• eat insects in flight, finding them through echolocation
• are known to share roosts in caves
• mate in late fall; give birth to one pup in April or May
• babies are nursed and raised in large maternity colonies
• baby bats learn to fly at 3 weeks old
• have a live span of about 15 years

suzanne@thepicayune.com