WILD THING

Wait Until Dark

CAVE MYOTIS stay behind to emerge after their Mexican freetail roommates.

by Russell Roe

At Old Tunnel State Park and other Hill Country caves, a second, lesser-known bat emergence occurs after the millions of Mexican free-tailed bats have taken flight and the bat-watching visitors start to leave.

Cave myotis (Myotis velifer) wait until dark, after the other bats have left the roost, to make their silent exit into the night. Even if you’re the kind of person who sticks around until all the credits have rolled after a movie, you might not notice the cave myotis. They’re hard to see in the dark, for one thing, and they fly closer to the ground in search of one of their favorite food: mosquitoes.

The cave myotis is a colonial, cave-dwelling bat that roosts in clusters numbering in the thousands rather than the millions (as seen with Mexican free-tailed bats, with whom they often share the same Hill Country caves). Colonies of 1,000 to 5,000 cave myotis are typical. In Texas, they can be found in the Edwards Plateau, Panhandle, Trans-Pecos and South Texas.

“At Old Tunnel, the cave myotis do come out separately,” says Superintendent Nyta Brown. “Inside the tunnel, they roost separately. It’s like that for myotis and freetails in many of the sites where they share a roost — the two species roost in separate areas rather than mixed in with one another.”

Cave myotis are about the same size as Mexican free-tailed bats, but their wingspan is shorter and broader. This means they can’t fly very fast or very high, but they’re maneuverable, able to fly through trees. In addition to mosquitoes, they eat moths, butterflies and beetles.

They have brown/black fur with paler undersides, and short, pointed ears.

Cave myotis typically mate in the fall, delaying ovulation and fertilization until spring and birthing one pup per year in late April and May.

Caves provide their preferred roost sites, although myotis also use buildings, bridges and culverts. They are crevice dwellers, seeking pockets and holes in the ceilings of their underground retreats.

In the winter, some hibernate in caves in Central Texas, and some migrate north to hibernate in the Panhandle.

As a hibernating species, cave myotis are susceptible to white-nose syndrome, a devastating disease that has killed millions of bats in the eastern parts of the United States. In 2019, biologists reported finding high levels of the fungus that causes the disease on cave myotis at several Central Texas locations. In 2020, an infected cave myotis — found dead in Gillespie County — became the first confirmed case of white-nose syndrome in Texas.