It’s a neighborhood mystery that seems to roll around about this time every year. You’re enjoying a warm summer evening outside when you hear a loud, high-pitched chirp. Or maybe you’d describe it as the sound of rubber-soled shoes on a gym floor. Or is it the call of an unfamiliar insect?
GettyImages/Brett Hondow
Mystery solved: Let’s all welcome the Rio Grande Chirping Frog (RGCF) to the neighborhood.
For Lakewood Heights neighbor Brina Tignor, her search began in the house. “The first time I heard them, I thought the smoke alarm battery was dead, and the alarm was beeping.” She eventually traced the sound to her yard, posted a video on social media and got plenty of suggestions for what it could be, including the possibility she was hearing the Rio Grande Chirping Frog. She listened to a recording online and knew it was a match.
But finding the little guys was another matter. “I tried to see them with a flashlight, but they’re so elusive. Maybe they’re attracted to our fountain?” she wonders.
Perhaps Sam Kieschnick, Urban Wildlife Biologist with Texas Parks and Wildlife, can shed some light. “They’re quite small and secretive, despite that constant song,” he agrees. “They’re maybe around an inch in length, and I usually see them hiding under potted plants or in rocky cracks.”
He explains that these little brown frogs are native to the Lower Rio Grande Valley and northern Mexico, and have made their way to this area by hitchhiking on nursery plants.
They’re readily identified by their distinctive vocalization. “They have these little ‘chirps’ that sound sort of like birds or squeaky toys, but after a little bit of rain or some humidity, you’ll hear this chorus all around.”
He adds, “I also notice them singing in the nights (usually summer, or at least when it’s above about 70 degrees) after I give my plants a good watering. They’re little bug eaters, so I consider them beneficial, even though I really do love bugs in general.”
But Kieschnick adds this reminder: “As amphibians they’re likely quite susceptible to pesticides — either themselves getting the poison in their skin or by getting the poison by the insects that they eat. Reducing pesticide use is much better for the entire ecosystem, in my biased opinion.”
So what’s special about the Rio Grande Chirping Frog besides its unusual call? This fun/weird fact is offered by biologist and frequent Master Naturalist educator Carlos Hinojos: Unlike other frogs, the RGCF does not have a tadpole stage; the eggs hatch directly into small frogs. “Their evolutionary history has decoupled their life cycle from water sources so that they no longer go through a full metamorphosis and instead undergo direct development.”
This also explains, in part, how they’ve spread across Texas. The frogs prefer warm, moist soil for their eggs, a soil much like those found in greenhouse plants. Explains Hinojos, “As these plants were sold and transported to various areas across the southeast U.S., the eggs and froglets joined.”
East Dallas neighbor and Master Naturalist Whitney Wolf first became aware of the RGCF several years ago. “I started hearing chirping at night when we took the dogs walking around the neighborhood. The chirping has always sounded like sleepy birds to me. As a long-time birder, I knew that was unlikely,” she remembers. She conducted a bit of detective work and found recordings of a frog with an identical call, but every range map in field guides didn’t show them in North Texas.
She was on a quest, she admits, to find the tiny and elusive RGCF. “I annoyed everyone I knew,” she laughs, “with stories about the RGCF and playing its call for them.”
Sometime later, Wolf attended a master naturalist meeting in Corpus Christi, where one of the training sessions was about frogs. She learned that the Rio Grande Chirping Frog had extended its range into North Texas but published field guides hadn’t caught up yet.
It was at this conference that she finally glimpsed the frog. “They were having a mothing event (i.e. — attracting, observing, photographing, identifying and documenting moths, according to the National Moth Week website) led by Kieschnick. And they found a Rio Grande Chirping Frog. It’s the only one I’ve ever actually seen.”
Wolf is glad to help clear up the mystery. “Any number of my friends and neighbors have asked me about the ‘bird chirping at night.’ They’re surprised to learn it’s a tiny frog making that peeping noise. RGCFs have been living in my yard for years and even survived Icemageddon.”
Kieschnick is another who happily coexists with the little frogs. “I think they’re just another critter that has adapted to the urban ecosystem to live amongst us — they’re using our habitats to thrive as they eat little tiny bugs. I definitely welcome them in my yard!”
