Spotted Chorus Frog vs. Squirrel TreefrogPseudacris clarkii vs. Hyla squirella

If I had to choose the species whose calls give me the most trouble in Texas, I'm embarrassed to say it is these two species - the Spotted Chorus Frog and the Squirrel Treefrog.  The strange thing they don't look anything like each other, they don't overlap much in range and most of the time they are easy to tell apart by call.  But occasionally, I hear one of these species calling by itself and it stops me and leaves me confused.

Let's start with a little introduction to our players:

The Spotted Chorus Frog (Pseudacris clarkii) is a small hylid of the grasslands and prairies of the south-central US.  The are found in prairies and marshes but also can be found in some agricultural fields and roadside ditches.  In these areas, they are usually only seen after heavy rains flood their fields and they come out to breed.  During dry periods they apparently burrow into the soil and are rarely seen.  They are small light grayish frogs with green spots and can be quite attractive little critters.

Interestingly, Spotted Chorus Frogs change color slightly between the day and night.  In the day the frogs are pale gray with brownish-green spots.  At night, their background color lightens making them a whitish frog with brighter green spots. I don't have a great photo of this, unfortunately, because Spotted Chorus Frogs tend to call from deep within mats of flooded grass.

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Squirrel Treefrogs (Hyla squirella) are quite a different looking little frog.  Like other "treefrogs", they have enlarged toe pads and vary from brown to bright green.  They also can change color depending on their activity states.  When they are very active and calling they are often bright green with a white stripe on their upper lip.  When cool or resting they tend to be tan or brown with or without brown markings.

So looking at these photos, you can see that these species don't really look that much alike.  And over most of their range, they do not overlap.  But in east-central Texas and down along the central Texas coast both species can be found together.

Where they do overlap in range, the problem is not their appearance but the sound of their calls.  I had been recording calls for several years in east central Texas before it occurred to me that their calls were similar enough to be confusing.   

One day in May 2015, I was at Aransas National Wildlife Refuge recording some frogs after a heavy rainfall and I made the following recording.  The temperature was 72°F:

In my notes, I documented this as a chorus of Spotted Chorus Frogs since this is a species I frequently hear during rainy summer periods in this area.  However, as I listened to the recording later that evening, I started to wonder if these could have been Squirrel Treefrogs which also occur in these coastal marshes.  I began to doubt my ability to discriminate the calls and that made me go back and check all my recordings from their region of overlap.  (It turns out I was correct at first, and these are Spotted Chorus Frogs).

The call of the Spotted Chorus Frog is a upward "fingernail over comb teeth" call.  But the speed of the call is correlated to the ambient temperature, so when it is cool out, the call is slower.  Here is a recording of some Spotted Chorus Frogs in San Antonio, Texas at 62° in March  -

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The call of the Squirrel Treefrog is an almost duck-like quacking sound and is typically faster than the trill of the Spotted Chorus Frog.

So even though the quacking sound is "different" than the trill of the Spotted Chorus Frog, as the temperature increases the trilling of the Spotted Chorus Frog becomes faster.  As that happens, they two species sound more similar.  

If you hear them together they are easier to tell apart..  Here is a Spotted Chorus Frog calling at the same time as a Squirrel Treefrog.  There is also the slow upward "fingernail on comb" call of the Cajun Chorus Frog (Pseudacris fouquettei) in this recording.

Here is a spectrogram showing you what you are hearing in this recording.

Here's a recording of a pair of Squirrel Treefrogs followed by a recording of some warmer Spotted Chorus Frogs.  You can see that although they are clearly different when heard with each other, they are similar enough that in the area of their overlap in range, you might have to listen carefully.

Squirrel Treefrog vs. Spotted Chorus Frog comparison

Fortunately, the area of overlap in range is pretty small.  Here's a map showing which counties have records for Spotted Chorus Frogs (yellow), which counties have records of Squirrel Treefrogs (blue) and which counties have records of both species.

So I'm working on these two species to try and be better about telling them apart.  I do that by getting out in the field when I can, but also by listening to the recordings posted on Inaturalist.org.  My goal is to be able to distinguish them immediately 100% of the time.  I'm not quite there yet.

Interestingly, I was listening to a record I had posted in some citizen science databases as Spotted Chorus Frogs and realized there were both species calling together.  See if you can distinguish the lower quacking Squirrel Treefrogs from the higher trill of the Spotted Chorus Frogs.

iNaturalist Record 8757877

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© Chris Harrison 2016

Texas' "Green" TreefrogsHyla cinerea vs. Hyla squirella

Texas has two species of green treefrog that are common in the eastern parts of the state.  One species is the well known Green Treefrog (Hyla cinerea) which is widespread across the eastern 40% of the state while the the other is the slightly smaller and less well known Squirrel Treefog (Hyla squirella) which has a more limited distribution in eastern Texas and along the coast.

Where they overlap, the species can be confused.  Both species are bright green "treefrogs" with a white stripe on the upper lip and paler undersides.  Telling them apart can be hard to the first time observer and sometimes even the seasoned veteran.  The problem is that while Green Treefrogs have roughly the same color and pattern over much of their range, Squirrel Treefrogs can be colored like Green Treefrogs or they can be brown or tan and look nothing like them.

Their colors can also vary.  Both species are brighter colored when they are active and calling.  When not active, the Green Treefrog (Hyla cinerea) is a darker green color.  Some Hyla cinerea also have yellow or orange spots on their backs.

Actively calling Squirrel Treefrogs (H. squirella) are typically green, but when not calling they can be plain brown or gray or have faint mottled patterns on their backs.

Here is a Green Treefrog (Hyla cinerea) from Grimes County, Texas.

Here's a greenish Squirrel Treefrog (Hyla squirella) from the Panhandle of Florida -

There are a few tips that help distinguish between Green and Squirrel Treefrogs. 

First of all, there is a difference in adult size.  On average, a Squirrel Treefrog is roughly 2/3 as big as a Green Treefrog, but they do overlap in size.  A small Green Treefrog can be the same size as a large Squirrel Treefrog.

While both species can have a white stripe running from the upper lip and down the side of the body, in Green Treefrogs it is conspicuous on the side with clear borders.  In the Squirrel Treefrog, if that line is present it is much more jagged and indistinct.  That is evident in the two photos above.  The line does not necessarily have to go all they way down to the "hips".  Many of either species can have the line fade out halfway down the body, as seen in the Green Treefrog above.

Another character that can be helpful is that the Green Treefrog (H. cinerea) there is often green pigmentation below the white stripe whereas the Squirrel Treefrog appears to have to green stop at the white stripe.

In the following photo you get to see another character difference that sometimes helps separate the two species.  In the Green Treefrog (H. cinerea), the upper body is bright green (with or without yellow/orange spots).  In Squirrel Treefrogs (Hyla squirella), the upper side may be bright green, but there are often remnants of a darker spots, a dark mask or at least a dark "eardrum" (tympanic membrane).  In the green treefrog, the tympanum is usually green like the rest of the frog.

The Green Treefrog is noticeably larger than the Squirrel Treefrog, but that can be hard to determine when looking at a small Green Treefrog by itself.

When calling, the Green Treefrog is usually elevated from the ground a bit.  They call from up on vegetation, branches, tree trunks, fence posts, etc. over the water.  They are generally perched within 2-3 feet of the water.  

Squirrel Treefrogs tend to call from the ground at the edge of the water.  This rule is not absolute, however, as I have seen Green Treefrogs calling from the ground occasionally as well.

But the sounds of their calls help distinguish them even at a distance.     

The Squirrel Treefrog (H. squirella) has an almost duck-like quacking call.  When I lived in South Carolina, some local residents called this species the Rain Frog for its habit of calling during and after daytime rains.

Here is a Squirrel Treefrog duet from Bee County, Texas.

The Green Treefrog (H. cinerea) has more of a "honking" call.  I always think it sounds like they are saying "WRENK, WRENK, WRENK".   Here is a group of Green Treefrogs from Fayette County, Texas -

Here is a recording of the "quack" of a Squirrel Treefrog (H. squirella) followed immediately by the call of a Green Treefrog (H. cinerea).  This was recorded in a roadside ditch in West Orange, Texas.

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It might be worth mentioning here that there are two other species of treefrog in Texas that can be "green".  These are the two species of Gray Treefrog (Hyla versicolor and Hyla chrysoscelis).  When they are green, they usually show some mottled "tree bark" type pattern -

or even when they are mostly green, they show orange coloration on the thighs that helps distinguish them from our truly "green" tree frogs.

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© Chris Harrison 2015

Cajun and Spotted Chorus FrogsPseudacris fouquettei and Pseudacris clarkiiwith Squirrel Treefrog Hyla squirrela

The pine woodlands of east Texas are home to the Cajun Chorus Frog (Pseudacris fouquettei).  It is sometimes still known by its older names of the Upland Chorus Frog (P. feriarum) or Western Chorus Frog (P. triseriata).  This little striped chorus frog has a call like someone running their fingers over a comb.  They call during the early spring and into the fall any time there is appreciable rain in their range.  They will call from flooded areas in the forest or along flooded roadsides.

Cajun Chorus Frog (Pseudacris fouquettei)

A little further west, the Spotted Chorus Frog (Pseudacris clarkii) takes over in the grasslands and prairies of central and coastal Texas.  Its call is a higher pitch, faster "creeeek" call than the other chorus frog.

Spotted Chorus Frog (Pseudacris clarkii)

They are not generally found together in the same habitat, but I came across this flooded field in Fort Bend County, Texas where both species were calling together.  There were also Squirrel Treefrogs (Hyla squirrela) in this chorus.

You can clearly hear the deeper, slow "fingernail over a comb" call of the Cajun Chorus Frog with the shorter, faster higher pitched "creeeeek, creeeeek, creeeeek" of the Spotted Chorus Frog above it.  You also hear the almost duck-like quack of the Squirrel Treefrog mixed in.

Here's a section of a rather dirty spectrogram showing these calls.   The lower pitched quacking sound underline in green is the Squirrel Treefrog (Hyla squirrela).  The lower pitched sound like a fingernail over a comb underlined in red is Cajun Chorus Frog (P. fouquettei, marked feriarum).  The short "creeeks" underlined in blue are the Spotted Chorus Frogs (P. clarkii).

Here is the recording of that particular section.

© Chris Harrison 2012

Squirrel TreefrogHyla squirella

The Squirrel Treefrog (Hyla squirella) is a well known frog of the southeastern United States.  In many areas of the southeast, they are known as "Rain Frogs" for their propensity to start calling any time of the day or night that it rains.

The Squirrel Treefrog is a frog of the southeastern United States but in Texas it is restricted to east Texas and along the Gulf Coast.  In Central Texas, Hyla squirella is reaching the edge of its range and they are not nearly as common or as well known as some of the other treefrog species around here.  The single record in Atascosa County, Texas is intriguing to me and I would like to be able to figure out where it was documented.  I have heard a lot of frogs calling in that county but never a Hyla squirrela.

The call of the Squirrel Treefrog has been likened to a squirrel (thus the name) or a nasal duck-like quacking.

Here are a pair of Squirrel Treefrogs calling in duet from a roadside ditch in Bee County, Texas.   These duet type call patterns are common in many Treefrogs.  The first male will call on one pitch and the responding male will call on a slightly higher pitch, probably to distinguish his call from that of his competitor.

Here is a section of the spectrogram for that duet.  You can see how the respondent's call is similar, but at a slightly higher pitch.

Here is a short video showing a Squirrel Treefrog calling from a flooded roadside near the entrance to Everglades National Park, Florida.  (You can hear the nasal whines of the Eastern Narrow-mouthed Toad and the "craack" of the Cuban Treefrogs in the background).

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© Chris Harrison 2012 & 2018