When you think about Texas caves, do you imagine impressive karst caves, filled with intricate limestone features like soda straws and cave bacon? Or how about about Bracken bat cave, and the millions of free-tailed bats that live there? Those caves are deep in the heart of Texas, too far south to be used by most hibernating bats. On a recent survey for white-nose syndrome (WNS) we were in north Texas, in the panhandle, and it was cold! I was grateful for my coveralls, as they provided another layer against the biting wind.
This is the third year in a row that Bat Conservation International has done WNS surveillance surveys for the Texas Parks and Wildlife Department. Gypsum caves in the panhandle look nothing like karst caves in the south. Some reminded me of slot canyons in Utah, formed by the rushing water of flood events. Others, I cursed, as they required an hour of crawling on my hands and knees.
As much as I would have enjoyed spending more time there, we were on a mission. The nearest WNS-suspect county is in western Oklahoma, not far from where we were. Which is why we chose to monitor these caves; if WNS is going to arrive in Texas, we think it will come from the north. Previous surveys hadn’t detected WNS or the fungus that causes it. We hope this year will be no different.
We are working with researchers at the University of California, Santa Cruz on a national survey for the fungus that causes WNS. The researchers will look for more than just the fungus’s presence. They will examine fungal load and transmission on a continental scale. The data we collect will be a part of a large dataset. It will also be the only data from Texas, and some of the only samples from cave myotis.
On this day, we visited a site that is a hibernaculum for the cave myotis (Myotis velifer). The last visit had almost 3,000 bats. We hoped that this year would be the same. This cave has almost 3,500 feet of passageway, and the bats roost all the way in back. So we had quite a trek. We changed out of our hiking boots into our rubber wellies and loaded all our gear into cave bags, which are easy to decontaminate. We headed in.
After 20 minutes of walking underground, we finally saw our first bat. It was a big brown bat! A surprise, as that species hadn’t been recorded in this cave before. Not much further, and we saw our first cave myotis. Then we saw a few more. We started counting. Soon, there were too many to count with the naked eye. Cave myotis sometimes roost in large, dense clusters. To count them, we took high-resolution photos of the clusters, and then count individual noses back at our computers. It’s tedious, but we get a more reliable count that way.
We worked in two teams of two. One team counted – one person, head up, eyes on the ceiling, gave the count: “2, 4, 13, 7, 1, 1, 3, photo 6654, 4, 2, 1, photo 6655, 12…..” Another, wrote it all down so the observer never lost track of where she was on the ceiling. The other team took samples.
We used sterile swabs, which look like large Q-tips, and sampled individual bats as well as the cave walls where they roost. The swabs were safely stored and marked for identification. We were careful not to contaminate anything. We placed a data logger in a nearby crevice. It will record temperature and humidity for the next year, until we return to pick it up.
As we finished, the bats were waking up. It can’t be helped, as these surveys take time; but the data is worth the disturbance. We headed back out of the cave. It took us over two hours to do the survey and take our samples. We hiked back to our truck in the dark-which was of no concern, as we’d been hiking in the dark, underground, most of the day. We removed our gear and place it in bags to be decontaminated.
I organized the datasheets and samples. We had no idea how many bats were in there. The large clusters were too many to estimate, so we’ll have to wait until we review the photos. But I added up the partial counts anyway, because I was curious. Over 2,000! Surprised, I shared this with the team. We were excited, as the cluster counts will surely double that number.
None of the bats showed any sign of the fungus or the disease. We’ll wait to hear back from the lab to confirm this, but were content for the day. The wait for WNS in Texas will continue another year.