As night falls in the Big Thicket, look upward and you may spot a bat or two, swooping through the woods in search of insects. The only mammals capable of true flight, bats take to the skies in the evening during the warmer months.

a researcher raises a pole that contains a bat monitoring device
Researchers use microphones mounted on poles to record the sounds of nearby bats.

NPS Photo / Ian Kessler

Bat Monitoring

In 2021, the NPS conducted research about the variety of bat species that inhabit the Big Thicket. Using different kinds of equipment, researchers have been able to detect and confirm the presence of eight bat species so far (see list below). The research is ongoing and more species will be added here when they are confirmed.

To detect the bats, researchers use a special microphone that can record bats' echolocation calls. The microphone is either mounted to a 12-foot pole or attached to a tree trunk. After recording for a few nights, the recordings are analyzed using software that identifies the calls by species. (Each bat species has a unique call, similar to how birds have unique calls.)

The Big Thicket's dense woods make bat detection more challenging than in other locations, such as the desert. Researchers choose locations within the preserve that will give the microphones a better chance of recording bats, such as clearings, riverbanks, and pipeline right-of-ways.

Read more about bat research methods at the North American Bat Monitoring Program.

Confirmed Species

Eight bat species have been confirmed during bat surveys:

  • Big brown bat Eptesicus fuscus
  • Brazilian free-tailed bat Tadarida brasiliensis
  • Evening bat Nycticeius humeralis
  • Northern yellow bat Lasiurus intermedius
  • Rafinesque's big-eared bat Corynorhinus rafinesquii
  • Silver-haired bat Lasionycteris noctivagans
  • Southeastern myotis Myotis austroriparius
  • Tricolored bat Perimyotis subflavus

Unconfirmed—More Research Needed

The following bats' calls were detected but more research is needed to confidently confirm their presence:

  • Eastern red bat* Lasiurus borealis
  • Hoary bat Lasiurus cinereus
  • Seminole bat* Lasiurus seminolus
    *The eastern red bat and Seminole bat have very similar calls. More research is needed to determine which species is present (possibly both).
a big brown bat roosting on a wooden beam inside a building
This big brown bat was found roosting inside a building. (Photo from Pipestone National Monument, Minnesota)

NPS Photo / J. Borden

Bat Behavior

In contrast to the large bat colonies found in central and west Texas, bats in the Big Thicket tend to roost in smaller groups. Some bats, like the northern yellow bat, prefer to roost in Spanish moss, which is abundant in the bald cypress trees along Big Thicket's waterways. Other species roost in tree hollows, crevices behind tree bark, and in manmade structures such as bridges and buildings.

Big Thicket's bats feed on many kinds of insects, including moths, beetles, mosquitoes, ants, and even cockroaches.

Bats often forage along waterways, such as the southeastern myotis, which catches insects as it flies low over the water. According to the preliminary results of our bat study, the water's edge habitat had the most diversity of bat species. Others prefer to forage high up in the trees, like the big brown bat, which forages among the treetops.


Bat Research in the National Parks

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    Last updated: September 3, 2022

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