Click it for crickets
Why volunteers count bugs in caves at the Balcones Canyonlands Preserve
Thirty minutes. Nothing yet.
Sitting in the dark, a biologist and a volunteer hold flashlights that shine red light while they stare down into the opening of a small cave.
Finally: “There’s a cricket nymph,” says Travis Clark, a natural resources specialist with Travis County. “Those are sneaky dudes. He went right underneath this rock." Then, shortly, he points to that same minuscule critter with long antennae as it crawls out. “You see that?”
Now the number totals one lone cricket.
Then it’s back to waiting and chatting while scanning the area around a steel covering with wide slats atop the cave entrance, roughly 2 feet by 2 feet. So far, it seems like a slow start for cricket counting at Tooth Cave, part of the Balcones Canyonlands Preserve.
Turns out the number of crickets — and whether it's up or down — plays a role in monitoring the health of the caves on the preserve.
While waiting for crickets under a nearly full moon, volunteer Jordan Jones, 26, sits on a cushion, shooing away mosquitoes and looking at numerous daddy long legs bouncing along.
Jones, who has a degree in environmental studies, doesn’t mind. “They are just little bugs,” she says. “They’re really cool little guys.”
Prepared for the count on this recent May night, they wear stretchy headbands that hold red lights (to not affect the cricket exits). In the dark, these red lights over their foreheads offer a dim glow, like a campfire.
Jones hardly needs to use the palm-size clickers in her left and right hands to help keep track of crickets. For this two-hour session, which starts at sunset, she can usually keep a mental tally during each 10-minute increment, when the numbers of nymph, juvenile and adult crickets are logged on a data sheet.
Then more waiting.
“Usually you can at least see their little antennas poking over the edge,” says Jones, who is experienced and on her third cricket count.
During exit counts at various caves, Clark says, he uses a system, some variation of holding a clicker in one hand to count the juveniles (5 millimeters to 12 millimeters) and holding a clicker in the other hand to keep count of the nymphs, which are up to 5 millimeters, or “up to the size of a grain of rice.” Then in his head, he can keep track of the adults (more than 12 millimeters).
This particular night offers several false alarms, though. Was that a cricket? Nope. They see a moth, a beetle, a shadow.
No more crickets yet.
“Sometimes you come out here and your crickets are going crazy, and sometimes it’s like this,” Clark says.
Suddenly, an adult cricket appears. “I just looked down, and he was there,” Jones says.
So far, the tally is one adult, one nymph.
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Among the highest cricket exit counts for caves managed by Travis County on the preserve was about 2,500, Clark says; the lowest number has been zero. (However, a cave count elsewhere in Austin has had counts of more than 11,000, he says.) When that happens, he says, the clickers are constantly going “click, click, click.” If a cricket goes back into the cave, he says, “You have to subtract it, or you don’t count the next one.”
Caves with larger openings can be trickier. “You have to be constantly scanning,” Clark says.
The scientific names for these crickets on the preserve are Ceuthophilus cunicularis, which never leave the cave; however, Ceuthophilus secretus and Ceuthophilus “Species B” exit the cave at night to eat organic matter, such as fungus, Clark says.
These crickets don’t necessarily look or act like crickets that most people would know for jumping around or performing choruses of chirping at night.
“I’ve actually never heard them chirp,” says Clark, who has worked full time for Travis County since 2015.
“Most of the time, (the crickets) are normally adhered to the ceiling (of the cave),” he says. As far as jumping, “They’re walkers. They’re only going to jump if they need to escape something.”
Regarding their leggy looks, “They are not like the black field crickets. … They don’t look like that at all," Clark says. “They live in a very dark place and feed at night, so they have longer appendages, longer antennae”; some have backs with a pattern that “look like a Rorschach test,” too.
So, why count crickets?
Tooth Cave is one of many caves on the more than 32,000 acres at the Balcones Canyonlands Preserve in western Travis County. The preserve was created in 1996 “as part of the Balcones Canyonlands Conservation Plan to mitigate the development of endangered species habitat in Travis County. The (preserve) was created to protect eight endangered species,” according to an overview of the preserve by Travis County. Those species included two birds (one has since been taken off the federal list of endangered species, though its habitat is still protected at the preserve), according to the overview. The other six species are cave-dwelling invertebrates (“karst invertebrates”) found only in Travis and Williamson counties; these are the Tooth Cave spider, Tooth Cave ground beetle, Tooth Cave pseudoscorpion, Kretschmarr Cave mold beetle, Bee Creek Cave harvestman and Bone Cave harvestman (five are found in Tooth Cave).
The conservation plan was approved by the U.S. Fish and Wildlife Service to protect high-quality habitat for these species at the preserve, said Johanna Arendt, community liaison with Travis County Transportation and Natural Resources.
This conservation plan identified 62 caves — including Tooth Cave — to protect as part of the preserve, which is primarily managed by the city of Austin and Travis County, as well as other partners. These entities have protected 50 of those caves to date and are working to add more to that list, according to Arendt.
But what about those cute crickets? They have a different significance here. They play an important role in determining the health of the caves on the preserve, Clark says.
The county began with quarterly cricket exit counts around 2005, but with more caves acquired, the current biannual counts started around 2010, according to Arendt.
“Cricket counts are a good way to get a good look at the health of the cave without having to go down in there,” Arendt says.
“It is part of our cave monitoring program,” Clark says. “Crickets are major nutrient source to the cave system. ... Essentially, they are a biometric of nutrients put into the system.”
Arendt adds: “The invertebrates that we protect in the cave live their entire lives in the cave. … The crickets go out and they forage, and they eat. ... A lot of species in the cave will eat the cricket themselves; they will eat their eggs and their droppings. So all of those nutrients are essentially from the outside, because those crickets go outside and eat. … By other species eating that cricket, it is taking in the nutrients that the crickets went out and got while it was foraging.”
Admittedly, the counters likely are not going to see each cricket. “It’s more like catching trends,” she says. For example, she says, if 15 crickets emerge during a count, but the count a year previous totaled 1,500 crickets, “that’s an indication there has been some change,” so they would investigate what’s happening.
“It’s a way to check on the cave ecosystem … without disturbing the cave ecosystem by going into the cave,” she says.
In one study, done in Coryell County, crickets were marked with “UV bright paint,” so they could be seen more easily, to determine how far the crickets forage from the cave, Clark says. That study found the distance to be up to about 105 meters (close to 345 feet), Clark said.
Travis County conducts these biannual cricket counts at 11 caves; seven counts are in winter and summer; the others are on a spring/fall schedule, Clark says. In addition, the city of Austin does cricket counts at caves at the preserve, according to Arendt.
“Their program exactly mirrors ours,” Clark says.
Tooth Cave, he says, has five of the six endangered karst invertebrates that are protected on the preserve, as well as three species of concern.
While a cave is “a specific structure, an opening or a void,” Arendt says, a karst system is characterized by caves and sinkholes, and other formations, in limestone.
Setting up and waiting
Tooth Cave, near the intersection of RM 2222 and RM 620, is a short trek behind a tall, locked gate with a “no trespassing” sign. Getting up close requires walking a rough path, over branches and leaves, past wildflowers and cactuses. All this helps to dissuade trespassers, Clark says. That’s a reason for the steel barrier covering the cave opening, he says, and specific cave locations aren’t given out.
When they first get there, Clark sets up a red light on a tripod and another red light, also outside the cave. Before the count starts, he measures the air temperature (71 degrees) and the humidity and checks cloud cover.
Clark and Jones each choose a side of the opening to watch out for crickets. The time of sunset is 8:16 p.m., and the timer is set, with a phone alarm that goes off every 10 minutes.
Then they wait, listening to traffic in the distance, as well as the sounds of nature: Clark hears a common nighthawk, a cliff chirping frog and plenty more. They stare down into the cave, which is about 18 feet deep, and 60 feet wide by 166 feet long, Clark says. (“A lot of people expect them to be big caves. Tooth Cave is one of the bigger caves, but it’s pretty small,” Arendt says. “There are some that we have that you literally have to wriggle your body down into it.”)
Over the years, Clark says, he has been on “many dozen” cricket counts. “I can’t even think of a number.” During that time, he has seen plenty of other wildlife, such as salamanders, white-footed deer mice, sometimes raccoons and “your occasional snakes.” He’s also heard great horned owls “barking … almost like a scream.”
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Jones, who lives in South Austin, says she got involved in the past year because she had been working in an office, and “I really missed having biology, science and nature in my life.” She says this is a good outlet with a minimal time commitment. The training is brief, at the beginning of the count, and that's when she got information on the sizes of the crickets.
Volunteers are needed because the preserve has a small staff, Arendt says. “We literally need the help, and also it’s a really interesting way to connect people in the community with the preserve.” In addition, volunteers bring different perspectives and skills.
In the past three years, nine women and five men have volunteered with cricket counting, according to Arendt. This activity is not a large part of the preserve’s volunteer program, which also includes deer and bird surveys and more.
Crickets don’t like cold temperatures, so Clark says he would cancel a count if it was below 55 degrees. On the first warm day after a cold snap, though, “They’re going to come out after that, when they are real hungry,” he says.
During some counts, “They kind of come in waves,” Clark says. “You’ll get a surge of them, and then another.”
But sometimes, these exit counts take patience.
“A lot of the cricket count is small talk,” Clark says. And waiting. Maybe whistling a bit.
On this night, more action happens toward the end. Jones discovers a nymph on the back of her jeans.
“It’s picking up,” Clark says, as he spots another cricket. “It’s Clyde,” he says, nicknaming one of them.
“Here’s a little juvy coming up,” Clark says. “Now that looks like a Species B, for sure. He just charged over.” Species B is more orange and does not have a pattern on the back, he says.
“There’s another nymph,” he says. “They’re cranking them out now.”
One adult cricket stands just inside the cave, where Clark coaxes it to come on “over the line, dude.” The cricket has to cross outside the cave to be counted, he says.
Cave management at the preserve also has other components, Clark says, such as using boiling water on red imported fire ant mounds. Periodically, Clark goes into caves flipping over rocks to “perform a survey to see in detail what the invertebrate community looks like on the inside of the cave.”
At the two-hour mark, the final tally is 42 crickets: five juveniles, 16 adults and 21 nymphs. It might seem like a slow night, but Clark says the total is typical for this time of year at Tooth Cave. (Two years ago, though, the count was about 1,200; “I think that was the anomaly,” he says.)
Clark takes note of the temperature and humidity again. Then it’s time to pack up.
Jones plans to volunteer at the preserve in some capacity in the future. She seems well-suited to the task. “It’s nice to hang out in a natural area,” and after all, she says, “my dog’s name is Cricket.”
For more information or to volunteer at the preserve, go to www.traviscountytx.gov/tnr/bccp/hikes-vol.