Meet Austin’s chirping frogs. They are everywhere, but we never see them.

It’s the curse of radio journalists. If you hear something mysterious, unexpected, or new, you want to get that sound. It doesn’t matter what time of day it is. It doesn’t matter what else you do. You want to capture it. What if you never hear it again? What if it was important? You must have it.

I’ve had this compulsion with a specific sound in my neighborhood for years. I hear it mostly, but not exclusively, in spring and early summer. And it’s not strictly speaking a single sound.

Rather, it is a collection of sounds that seem to come from the same source. It’s a sort of squeaky, leering, whistling, warbling high-pitched sound. It comes from trees, rocks, walls and yards. Sometimes it even seems to come from the ground. And it always seems to be the same animal that makes the noise.

This confused me because it seemed like it could be many different things, and reviewing the dozens of recordings I made couldn’t narrow down what was going on.

I thought they were baby birds tweeting in their nest. It can sound almost exactly like that, except there is a component of trills and crackles that comes into play to destroy the impression.

This squeak sounds like crickets or katydids, and for a moment I decided it must be a bug.

But the noises seem scattered and irregular. They don’t keep up with the insects. Sometimes they sound almost like a whistle, which I’ve never heard a cricket do.

I even briefly considered the idea that geckos were the cause. I had heard that geckos can make noises and that these noises started to be heard in the spring, around the time I started noticing them in my garden.

But some theories suggest less organic origins. One of my neighbors even thought the squeaks were coming from water pipes that were leaking or under pressure.

I’ve seen a lot of things in my yard: bugs, birds, snakes, lizards, toads, raccoons, and water pipes.

I’ve never seen a single frog.

It turned out to be frogs.

People hear frogs all the time but never see them

On the UT Austin campus, there is a place that Tom Devitt calls “the frog room.” It lives up to its name, containing shelves of terrariums each housing a different species of frog.

Devitt is a professor and researcher at UT Austin specializing in amphibians. After emailing experts about our neighborhood mystery, I was put in touch with him and he invited me into the frog room to reveal the likely source.

“A lot of people have never seen one, but you hear them all the time,” he said, dismantling a terrarium that appeared to be largely filled with a piece of limestone.

From inside this stone, Devitt brought out a small frog. It was an inch and a half long at most, tan in color with brown spots. It seemed very shy.

“This species is called the cliff chirping frog,” he said. “It’s a native species.”

Devitt calls them enigmatic. Small, good for hiding, hard to find.

That, he says, is the challenge of researching them: They’re really hard to observe in the wild. There are also different species of chirping frogs around Austin.

The frogs chirping on the cliffs favor the rocky outcrops on the west side of the city: hence the limestone. But Devitt suspects that what I heard in my backyard might be the song of frogs from the Rio Grande.

This is a closely related species that is more likely to take up residence in trees and vegetation. These are also more recent arrivals to Austin, perhaps coming from South Texas on potted plants.

“There was a big nursery in Brownsville, that’s kind of where they originated,” he said. “We think that’s probably where they came from, although we can’t be sure.”

Rio Grande chirping frogs have spread across much of Texas and Louisiana. Until now, they appear to have occupied a slightly different ecological niche than cliff frogs and offered little competition.

Frogs are everywhere, but not much is known about them

Chirping frogs aren’t like most frogs you’ve heard of.

For one thing, they don’t need a lot of water. There is no tadpole stage for these frogs. They simply lay eggs, and the young hatch directly into little baby frogs. This is how they can live in gardens, like mine, without a regular source of irrigation.

Because they lay eggs, they behave differently. While most frogs simply fertilize their eggs in the water and leave them to their fate, chirping frogs stick around and take care of them.

In fact, male frogs may well be the primary caregivers.

“They will kind of sit on eggshells. Move them,” Devitt said. “I think they’re usually just protecting them from predators, that’s the idea.”

They somehow survive Texas droughts and heat waves – probably because their metabolisms slow down. But how exactly this works and how they know when to do it isn’t entirely clear.

In fact, the more we talked, the more it became clear that there was a lot we didn’t know about these frogs. Even though they are everywhere.

“I just think it’s fascinating that we have biodiversity around us that we know almost nothing about,” Devitt said.

But he wants to know.

How exactly do they reproduce without water? How far do they travel in a lifetime? How long do they live?

“We have no idea,” he said.

In fact, we’re not even sure why they make these strange sounds.

“They make two types of calls,” Devitt said. “One is kind of a little trilling noise. The other is a sort of insect whistle or chirp.

A sound is probably used to attract mates. The other to guard the territory. But again, Devitt has to study them to find out.

“I want to know everything about these frogs and what it’s like to be one,” he said. “That’s what I do.”

To do this, you need to find them.

So it was a few weeks later. KUT photographer Michael Minasi and I joined Devitt at the Brackenridge Field Lab, off Lake Austin Boulevard, for a frog hunt.

Come frog hunting

The trail Devitt chose is perfectly suited to hunting cliff frogs. It runs alongside what was once a quarry, where stone blasting has exposed a limestone rock face, providing a perfect habitat.

Walking the trail at night, my microphone picked up insects, birds, wild animals rustling in the undergrowth. But one thing we didn’t hear much about was frogs chirping.

“As the season progresses, they go out less and less,” he warned.

Luckily, he didn’t need to hear them to catch them.

One by one, Devitt spotted the frogs, like shiny coins on the rock in the beams of our flashlights.

We found four that evening despite their reluctance to chirp. Some were very small, perhaps half an inch long.

“It makes me wonder if these are the ones that hatched this year,” he said.

He left the little ones alone. But he collected a male to bring to the laboratory.

He had hoped to see if the frogs would mate in captivity to learn more about how they reproduce and raise their young.

But when I called to check a few weeks later, he said he had no luck and sent them back into the wild.

He thinks he may have waited too long into the year and collected frogs that were no longer interested in mating.

One of the reasons for this theory? These great little frogs we found. If they were newly hatched, did they signal the end of the frog mating season?

“I don’t want to speculate too much,” he said. “But… it’s not that often you see little ones, and we saw a few pretty quickly.”

So instead of answers, we end this story with one more question about the mysterious chirping frogs of Central Texas.

Have we helped welcome the next generation of cliff warblers into the world this year, freshly hatched from a hidden clutch of eggs?

Right now, there’s no way to know. But Devitt plans to search for answers next year when that strange squeaking, whistling and chirping sound fills the air again.