20 million secrets waiting to be revealed.
09.02.26
By Steph Dodson
A breeze breaks the 100-degree Texas summer heat, and as it does, the strong scent of corn tortillas drifts over me.
Hold on a second . . . that’s not corn tortillas . . . that is the undeniable smell of nearly 20 million Mexican free-tailed bats (Tadarida brasiliensis) at Bracken Cave Preserve in Texas.
We are waiting for the emergence with our butterfly nets in hand, as we’ve done most months for the nearly the last three years (barring the occasional weather‑related cancellation). Tonight we will surpass bat number 700.
Netting New Evidence
Under the guidance of lead researcher and University of Oklahoma PhD student, Kristin Dyer, tonight we are “sampling.” The data we collect helps Kristin understand climatic drivers of these bats’ migration and the interactions between migratory timing, parasitism, and bat health. This research is why she is a 2026 Bat Conservation International Student Scholar — part of an international group of Masters and PhD students focused on evidence-based research of threatened and data-deficient bat species and critical habitats.
As the emergence begins, we head down to the mouth of the cave. August sampling is, by far, one of the easiest months to catch our furry friends, because the new pups have already started to fly. We are able to lift up our small nets and, with almost no effort, bats (of all ages) find their way inside. It takes three of us less than 10 minutes to catch 30 bats and settle them into their individual canvas bags so we can bring them to the field house.
In months like December, it can take 45 minutes to catch just ten individuals. Most have already migrated to Mexico for the winter. Why some stay behind, and whether others migrate to Bracken from farther north, are two questions Kristin aims to answer. Understanding these patterns helps us anticipate how climate change may reshape bat movement across the continent.
Fur-ensic Work
At the field house, Kristin has our stations set up with the instruments needed to collect our samples. Among the various tools are: a scale for weight, calipers to measure the forearm length, swabs to collect saliva and fecal matter, scissors to collect a small amount of fur, PIT (passive integrated transponder) tags to understand bat movements across the landscape, and forceps to collect ectoparasites. August is one of my favorite times to sample because we can more easily determine the age of each bat. Each of the bats have one of their wings gently opened to examine their elbow joint. If the joint isn’t fully fused and we can see light passing through it, then we know it is a juvenile who was born just 6 to 10 weeks ago. Understanding the life cycle from pup to adult, and how quickly they develop to fully grown, is absolutely fascinating.
Each sample tells us something unique about these historically misunderstood creatures — fur, saliva, fecal matter, and especially ectoparasites — each one a clue to the bats’ health, movement, and resilience.
“Each sample tells us something unique about these historically misunderstood creatures — fur, saliva, fecal matter, and especially ectoparasites — each one a clue to the bats’ health, movement, and resilience.”
Collecting fur gives us clues as to where the bats spent their last summer and whether they’ve been exposed to pesticides or other contaminants. As bats eat and drink, tiny chemical signatures are shown in new fur growth, creating an isotopic “map” we can compare across known habitats.
Their saliva helps screen for viruses; both those we already know about and those that may be newly discovered. It’s a way to understand whether bats are healthy, fighting infections, or carrying viruses that shift as they migrate.
Fecal samples and guano collection tell us what the bats are eating and provide another opportunity for viral screening. Diet gives us clues about ecosystem health, insect populations, and how bats adapt to changing environmental conditions.
PIT tags are very similar to the microchips you put into your pet, and each time a tagged bat is scanned, we learn where it has traveled. These tiny tags help us track movement across seasons and regions.
And the main star of Kristin’s research: the ectoparasites! These include bat fleas and bat flies, each belonging to their own unique taxonomic families, and found only on bats. Very little is known about them: where they go, how they move, and if they migrate right along with their hosts. These tiny hitchhikers may hold clues to bat migration routes that we’ve never been able to access before.
How to Speak Bat
After we have documented all of the measurements and samples we’ve collected (on our very detailed data sheets) comes everyone’s favorite part — releasing them back into the wild. One-by-one, as each bat has finished being sampled, they are taken back outside. Each release is slightly different; some fly away immediately, a few seem to have forgotten in the last couple of hours that they could fly at all and need a bit of encouragement to leave. And every once in a while, a bat will use your fingers to flip over, hang upside-down for a moment, then launch themselves into the night (those are my favorite, as acroBATics are incredibly fun to watch.)
For the safety of not only us, but the bats themselves, we follow strict protocols while handling them; such as always wearing masks and gloves and having preventative vaccines (just in case.) However, that doesn’t take away from our genuine curiosity and love for these tiny fuzzballs. Pretty much everyone at the table talks directly to the bats at one time or another. From telling them how adorable they are, to thanking a bat for their cooperation when they make collecting certain samples very easy, and in my case, always asking each bat to share their secrets with me.
My own research with this colony focuses on what drives the start time of emergence each night. Weather patterns, moon illumination, drought conditions — something is influencing dramatic shifts in the start of going out to forage each night. Each month, while I hold them, I ask them to tell me why. They squeak up at me as if they’re spilling everything. I just haven’t cracked the code to understand what they’re saying yet.
Partnerships between BCI and researchers like Kristin deepen our understanding of bat ecology and beyond. Until we can speak fluent bat, we will continue to study these riveting mammals and do our best to answer all the mysteries that will help us make the best choices for their conservation and protection worldwide.
Learn more about Kristin’s research
Join Bat Conservation International’s mission to protect and conserve bats worldwide
Bracken Cave Preserve is host to many research projects, not only on bats. If you’re a researcher who would like to explore the possibility of a project at Bracken, contact Krystie Miner at [email protected]
Steph Dodson is a conservationist, field researcher, and lover of all wildlife. She earned her Associates of Applied Science in Conservation & Wildlife Management from Austin Community College in 2025, is finishing her Bachelor’s of Applied Science with a focus in Conservation & Wildlife Biology this year from Texas State University, and starts her TXST Master’s of Wildlife Ecology next year with a focus on bats. Find her on Instagram @wildlife.conservation.steph
Krystie Miner – Project Coordinator
Krystie began working with BCI in January 2023 as the Project Coordinator for Bracken Cave Preserve. She coordinates volunteers to lead tours of Bracken Cave and to help with numerous other research, conservation, education, and citizen science projects. She also aids in other BCI projects as needed, including White-Nose Syndrome surveys and swabbing agave plants for eDNA.
Krystie has a background in wildlife research and conservation and has been working with bats since 2014. She has a B.S. in Ecology from Boise State University and an M.S. in Conservation Biology from Texas State University. She resides in San Antonio, Texas, where she is within a half hour drive to Bracken Cave and spends her spare time exploring the hill country with her dog.
