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| Greenhouse Frog (Eleutherodactylus planirostris) from Naples, Florida |
OK, so I've made a comparison entry before for the "Texas" species in the genus Eleutherodactylus, the Rio Grande Chirping Frog (E. campi or E. cystignathoides, if you prefer 😜) and Cliff Chirping Frog (E. marnockii). But there's a new chirper in town, the Greenhouse Frog (E. planirostris) and we need to figure out how to identify it as well.
The Greenhouse Frog is spreading through the state of Texas. It is most often transported as frogs or eggs in potted plants (thus the name "greenhouse"). It is originally from the Caribbean, but is well established in Florida and that is probably the source of their transport across the Gulf Coast and into Texas. In fact, this species has spread to China and Taiwan, Singapore, the Philippines, Guam, Hawaii and many places throughout Mexico and Central America.
The Rio Grande Chirping Frog is native to eastern Mexico and the tip of south Texas, but has also been spread north through transport of frogs and their eggs. They have been expanding their range in Texas over the last 40+ years. And their rate of spread can be quite quick. I remember looking for herps in west Houston in the late 70s and early 80s. I flipped a lot of trash but never saw these tiny frogs. But when I went back to those same areas in the mid 1980s, Rio Grande Chirping Frogs were abundant in the exact same places.
The reason these small chirping frogs in the genus Eleutherodactylus have spread so quickly is that they are natural invaders. Not only are they tiny and easy to move around, but they are quite comfortable living in forests, weedy brushy areas, suburban gardens or even potted plants.
But their most powerful invasion trick may be the fact that they have direct development. This means they have no aquatic tadpole stage and their eggs just hatch into tiny little froglets. Therefore the females don't have to find a pond or stream to lay eggs, they can just bury them in the soil of the potted plant they live in. So eggs and babies get transported easily, the new arrivals can breed in the buckets they were transported in,et voilà !, you have an introduced population of chirping frogs. It is worth noting that they are not known to be parthenogenetic (like we see in Brahminy Blindsnakes), so they still require a male and female or fertile eggs to be transported to establish a new population.
Previously, these little invaders were pretty easy to ID based on the fact that most areas only had one species or the other. So if you were in Florida, it was a Greenhouse Frog (E. planirostris). If you were in Texas, it was a Rio Grande Chirper (E. campi). But now these two invasives are starting to spread towards each other and overlap in range. Suddenly, just finding a small "chirping frog" doesn't always allow you to name the species.
Telling these two introduced species apart visually can be tricky. I should mention here that much of my attempt to explain how to distinguish these species is derived from my limited experience and a lot from Tom Lott's (2017) published explanations.
In general, some Greenhouse Frogs look noticeably different than Rio Grande Chirpers, others do not. Both species are small and variable in color. They are usually some shade of brown or greenish brown with some darker brown/black marks or reticulations on their dorsum. Some show yellowish or reddish patterns as well.
But the Greenhouse Frog seems the more variable. Some Greenhouse Frogs are brown, some are greenish brown, some are reddish brown and some are brick red. Like some other Caribbean Eleutherodactylus, Greenhouse Frogs also have a "striped morph" which has bold light stripes on the dorsolateral edge of the body. Rio Grande Chirping Frogs don't seem to have this morph?
Also notice the mid-dorsal line of tubercles seen in this photo. That is often another clue you are dealing with a Greenhouse Frog.
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| If your little chirping frog has stripes like this, it is probably a Greenhouse Frog. Rio Grande Chirpers don't show this color pattern. Photo of Greenhouse Frog by Eliot VanOtteren from this iNaturalist record and used under Creative Commons license conditions. |
One oft-cited difference is the colored "triangle" on the top of the head between the eyes and nose in the Greenhouse Frog. But the Rio Grande Chirper can often show this light triangle on the head, it is just not as pronounced or as contrasty as you see in Greenhouse Frogs. When it occurs in Rio Grande Chirpers, it is usually not much different in color to the rest of the body, just a bit lighter. In Greenhouse Frogs this triangle is noticeable different (usually much lighter) than the body color. Again, this difference is subtle but consistent.
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| Although this Rio Grande Chirping Frog (Eleutherodactylus campi) has a light triangle on its head, the dark mask helps us tell it isn't a Greenhouse Frog. Palmetto State Park, Texas |
One factor that might help distinguish them in areas of overlap is the present of a presence of a darker "mask" along the edge of their head through the eye (along the canthal ridge). The mask fades as you move down towards the mouth, so it almost looks like the top of the head is "shading" the side of the face. Not all Rio Grande Chirpers show this as much as others, but it is not usually seen in Greenhouse Frogs. Some Greenhouse Frogs show lots of dark spotting on the face and even a dark stripe, but this "shading" pattern is not usually seen.
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| The dark mask along the edge of this frog's head leads us to identify it as a Rio Grande Chirping Frog (E. campi) |
Another character that is sometimes give to help with the ID is the nature of the dark bar between the eyes (at the posterior edge of the triangle). In Greenhouse Frogs, this bar is usually quite thick and continuous. In Rio Grade Chirpers, this "bar" is made of a series of dark spots and usually broken in places.
To my eye, Greenhouse Frogs are also more rugose generally. While Rio Grande Chirpers can have small tubercle-like bumps on their bodies, their skin between those bumps is fairly smooth. Greenhouse Frogs have more "warty" skin with many more tubercles uniformly across their back. This is a really subtle difference and doesn't work all the time in differentiating them.
Another character that can help is the presence of a dark chevron on the back between the forelimbs (on the frog's "shoulders"). This dark arrow points backwards and is seen on many Greenhouse Frogs, but not on Rio Grande Chirpers.
Greenhouse Frogs seem to have a more narrow rostrum (more pointed nose) than Rio Grande Chirpers as well.
So, if you find a small Eleutherodactylus in its area of overlap that has no dark mask along the edge of its head and a prominent lighter triangle on its somewhat pointy head, it is likely to be a Greenhouse Frog. Otherwise it might be a Rio Grande Chirper.....maybe?
Here's a couple of good example frogs that look superficially similar:
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| This photo by Peter May, used under Creative Commons License, shows the combination of charateristics which can be used to ID most Greenhouse Frogs. |
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| This photo shows the combinations of characteristics which can be used to ID most Rio Grande Chirpers. |
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So they can be easy to tell apart, or not.
But of course, my blog is supposed to be about frog calls. So do their calls sound different?
Well, yes and no. Both species make a chirp and a trill call.
Here's a group of Rio Grande Chirping Frogs calling. You can hear a series of their chirps and their trills
And here's a group of Greenhouse Frogs from the Everglades in Florida.
Notice how much more complex the call of the Greenhouse Frog is. It is usually a double or even triple chirp ("ch-dip" or "chi-chi-dip") whereas the chirp of the Rio Grande Chirping Frog is a single "chip". In musical terms, the Greenhouse Frog plays one or two grace notes before most chips, the Rio Grande Chirper doesn't.
So while the Rio Grande Chirping Frog will make more than one chirp in a row, they are more spaced out. Take a look at this comparison spectrogram showing a Rio Grande Chirper followed by a Greenhouse Frog. The gaps between the double chirps are two to three times longer in the Rio Grande Chirper. Also the gaps between the chirp groups are shorter in the Greenhouse Frog (they are more "talkative"). You can see that the Rio Grande Chirper gets 5 chirps out in about 3 seconds, the Greenhouse Frog gets 11 chirps out in the same amount of time (actually it is two Greenhouse Frogs talking back and forth).
Here is the recording of that spectrogram. In the first five seconds you hear the chirps of the Rio Grande Chirper followed by the quick eleven chirps of the pair of Greenhouse Frogs.
So If you can learn to listen for the frequent double chirps of the Greenhouse Frogs in the areas where they overlap, you should be able to learn to hear the differences. You can't always identify one from a single chirp, but when they are calling repeatedly, they give themselves away. In a mixed chorus of both species, it would be hard once again.
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I started this blog post comparison about 10 years ago and am just now getting around to finishing it. This is obviously a complex comparison that I will have revisit in the future, but if I don't stop now, I might never finish. 😉
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© Chris Harrison 2025
Lott, Tom. 2017. Distinguishing between the Greenhouse Frog (Eleutherodactylus planirostris) and the Rio Grande Chirping Frog (Eleutherodactylus cystignathoides) (Anura: Eleutherodactylidae). Southwestern Center for Herpetological Research 7(4) pp. 69-75. https://www.southwesternherp.com/wp-content/uploads/2023/03/2017-SWCHR-Bulletin-Vol-7-Issue-4.pdf
