The Central Texas Chirping Frogs
Eleutherodactylus cystignathoides vs Eleutherodactylus marnockii


Central Texas is now home to two species of Chirping Frogs in the genus Eleutherodactylus.   Historically, the hill country region of Central Texas was the haunt of the Cliff Chirping Frog (E. marnockii).  These frogs reside in the rocky hills and canyons of the Edwards Plateau and west into the mountains of West Texas.   They range south into Mexico but their range is poorly known due to confusion with a very similar species that occurs south of the border*.


Known distribution of the Cliff Chirping Frog in Texas

However, over the last 25-30 years, another species of Chirping Frog has been moving in to the area.  The Rio Grande Chirping Frog (E. cystignathoides) was formerly restricted to the southern tip of Texas in the Rio Grande Valley and south into Mexico.  But this small frog has a propensity for living in gardens and being transported around the state in potted plants.  They have now spread into many cities of Texas and into the rural areas between the cities.  When I was a teenager in Houston in the late 1970s, there were no Chirping Frogs in the Houston area.   By the middle 1980s, they were abundant.  They are continuing to spread and should eventually be documented in all the wooded counties of the eastern half of Texas.  They have spread east into Louisiana and undoubtedly will end up being recorded in OK and AR eventually.**



Native and Introduced distribution of the Rio Grande Chirping Frog in Texas

The gaps in the map for the Rio Grande Chirper in south and southeast Texas are probably due to them not being documented there rather than not being present.  This is a tiny little frog that is easy to overlook and its call is often dismissed as being from a bird or insect.


Here is a map showing the two species ranges together.  The blue counties are those where only Cliff Chirpers are documented, the yellow counties where only Rio Grande Chirpers have been documented and the green counties are counties where both have been documented (although they usually occur in different habitats).   The two red counties represent records for Cliff Chirping Frogs that are questionable based the availability of habitat.  Rio Grande Chirping Frogs occur in both of those counties.




When seen as adults, these two species are reasonably easy to tell apart.  The Cliff Chirper is a noticeably larger frog with larger adults reaching the size of a quarter.  Their overall color pattern is a mottled brown/green on a darker background although they are highly variable.  Some are almost yellow in ground color, others can be very dark.  They usually have a darker line running along the snout to the eye.



Cliff Chirping Frog
Hays County, Texas
Cliff Chirping Frog
Crockett County, Texas


The Rio Grande Chirping Frog has a similar pattern and is again highly variable, but it is noticeably smaller as an adult.  An adult Rio Grande Chirper can sit on a dime and a huge adult would sit easily on a nickel.  Of course, a small Cliff Chirping Frog could be this size as well.


Rio Grande Chirping Frog
Bexar County, Texas

So if you see an adult, you can tell them apart.  But what about their calls?
Unfortunately, both species make a "chirping" call and a sort of "trill".  Here is a chorus of Rio Grande Chirping Frogs from Bastrop State Park.  You can hear both the high "chips" and the "trill" call in between.



Here is a recording of a Rio Grande Chirping Frog from Medina County, Texas - 





Here are a few chips and trills from the Cliff Chirping Frog from Real County, Texas - 



and another series of Cliff Chirpers from Kerr County, Texas -



The obvious difference between their calls is the frequency (pitch) of the calls of each frog.  Possibly because the Rio Grande Chirping Frog is much smaller, the calls of the Rio Grande Chirping Frog are noticeably higher in pitch than the Cliff Chirper.  Although the "trill" part of the call is lower pitched in both species, it is consistently lower in the Cliff Chirper than the Rio Grande Chirper.


Here is a recording of a series of chirps made first by the Rio Grande Chirping Frog and then a series by some Cliff Chirping Frogs.  Even though there is a tiny overlap in the call range, by listening to a series of calls you can distinguish them.  Only the highest of the Cliff Chirper calls approach the lowest frequencies of the Rio Grande Chirpers -



Here is a spectrogram of that recording.  The green line is approximately at 2700 Hz.  You can see that the Rio Grande Chirping Frog calls (the first series) are above that frequency while almost all of the Cliff Chirpers are below that frequency.




Both frogs also make a "trill" as part of their call and once again, the Cliff Chirping Frog's trill is noticeably lower in frequency (pitch) than that of the Rio Grande Chirper.   Here is a few seconds of the Rio Grande Chirper followed by a few seconds of the Cliff Chirping Frog.  The trills are a little tougher to tell apart so it is better to rely on the relative frequency of the "chirp" part of the calls.



Unlike most other Texas Frogs, these species do not breed in water.  The males call from terrestrial sites like cracks and crevices, from bushes or trees or just on the ground.   For this reason, people often don't recognize them as frogs since there may not be significant water nearby.  I have been contacted by people asking what species of bird is chirping in their backyards on moist summer nights.

After breeding the eggs are laid on land in a moist area.  The eggs hatch into full formed froglets rather than tadpoles as the whole tadpole stage is spent inside the egg.  Because they do not need open water for their tadpole stage, they easily adapt to living in suburban backyards, etc. and can be transported to new locations where they can set up and breed.  This is part of the reason for the success of the Rio Grande Chirping Frog in spreading across the eastern parts of Texas.



© Chris Harrison 2015



* Those looking in a field guide to US or Texas Amphibians might note there was another species formerly listed as occurring in far western parts of Trans-Pecos Texas called the Spotted Chirping Frog (E. guttilatus).  Recent research shows that E. guttilatus does not occur in the US and all west Texas Chirping Frogs are the same species, E. marnockii.


** To further complicate matters, there's a new frog in town as well!  The Greenhouse Frog (Eleutherodactylus planirostris) has now been documented in SE Texas near Galveston.  This species is almost identical to the Rio Grande Chirping Frog in size and pattern and their calls are very similar.  It might take some time to document the spread of this frog in SE Texas due to how difficult it is to tell it from the Rio Grande Chirper.

20 comments:

  1. I searched for a long time to identify a sound that I hear in the night when the windows are open. Finally decided it must be some very tiny frogs. Sometimes they are having a conversation. I live in a very dry area on the Edwards Plateau(Austin). Chirps are not as loud as the ones you have here.

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  2. reporting from Collin Co. we have them. i'd wondered for years if it were rats giggling when i took the garbage out to the bin.. but no, this am, i confirmed tiny frogs, as one hopped across my patio around 6:20A today, i guess froggy was 'goin a courtin' :) i can even get them to answer when approximating the chirp :) as the call is quite high, i'm guessing we have rio grands :)

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  3. Any idea how to get them out of my yard? They are keeping us up all night every night!

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  4. We recently had our entire backyard re-landscaped. I am fairly sure that Rio Grande chirpers are taking over. We are awake all night, every night. Any idea how to get rid of them?

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  5. Wow. We have chirping frogs too. Thought it may be RIO GRANDE but he is much bigger. My Pom caught him and held him as a pet. Set him free and must have gotten back into the poolyard. Caught him taking a late night swim last night. We also are in Collin County.

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  6. Thank you for this info! I’ve seen tiny frogs in my garden (Dallas Co.) but thought they were juveniles. Hear chirping all night & couldn’t figure out what it was. Amazing that such a small frog can make so much noise!

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  7. Wondered for years what kind of bird was chirping at night here in San Antonio. These tiny suckers are damned difficult to spot. At least now I know! =)

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  8. I listened to all of these in hopes one would sound like whatever lives under our deck. It sounds like a bird but has a repetitive HIC-up (or CHEEP_u) and on occasion sounds like a frantic cackle The local Ag rep is researching it I'm in Kerr County, TX. But I enjoyed listening to your video!

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  9. I wonder, are they on low vegetation, trees, or the ground. They are sounding right outside my window and I would love to spot one. Any advice? There is nothing right next to the window except some inland sea oats. The tree is about 12 feet away and branches are pretty high up. It is an oak.

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  10. Why would anyone try to get rid of these little guys. I find their chirps comforting. They aren't that loud, geez.. Buy a box fan to run at night, turn it away from you if its too cold. The white noise will drown out the chirps 😐
    You can also find white noise recordings (fans) on YouTube that are 11 hours of fan noise. Or, move to the city 🙄

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  11. Does anyone know for sure what their wild diet is? I'm looking for evidence from research articles.

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  12. Glad I found this! I couldn't figure out what was making the sound. I've also seen the little frogs in my yard along with other different larger ones. I am in San Antonio, Bexar County

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  13. I'm happy to find all this information. I,too, have had "conversations" with a chirping frog that comes right next to my window at 10:30 p.m. It chirps a particular pattern of chirps and trills, waits for me to mimick, then repeats the pattern again. We have kept it up until I can't go on because I'm laughing. I moved to Austin (Travis County) from New York City last year and I'm enjoying Texas wild life very much.

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  14. So happy to finally know what theses frogs are called!
    I searched for the source of the chirps for years in my Dallas yard and am always so happy to hear their first chirps in the spring and when I water the plants on my deck.
    I like to whistle to them and hear them answer back!

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  15. Ours were on the ground in dense vegetation and grass.

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  16. Heard the Rio Grande chirps for the first time here in east Parker County after our rare late August wet spell. Sounds like they are in the mountain cedars around the most often dry creek behind my house. Makes sense, if they have been found in Tarrant County just to our east.

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    1. Fortunately you don't have Cliff Chirpers up there so if you hear a chirping frog in the mountain cedars, it is this species. Further south it isn't that simple.

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  17. Is it known which types of potted plants these frogs are being transported in? Specifically,the plant species and where they are being transferred to in terms of nurseries?

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    1. I don't think they are specifically transported in any type of plant. They just like to live in the moist soil in large plant pots and around nurseries. So any time those plants are transported to "new homes".
      Many species of frog get translocated by the nursery industry (Cuban Treefrogs, Squirrel Treefrogs, Green Treefrogs, Greenhouse Frogs, and these Chirpers).

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