Frog Blog: May 2015

East Texas Toad
Anaxyrus "velatus"

The East Texas Toad is a problematic taxon. It has been variously recognized as:

a valid species - Anaxyrus velatus
a subspecies of Woodhouse's Toad - Anaxyrus woodhousei velatus
a form of Fowler's Toad - Anaxyrus fowleri
a hybrid between Fowler's and Woodhouse's Toads - Anaxyrus fowleri x woodhousei

So which is it? I don't presume to know. I do know these medium sized toads are fairly common in the woodlands of eastern Texas and western Louisiana. The problem is that their characteristics are somewhat intermediate between Woodhouse's and Fowler's Toads. Woodhouse's and Fowler's Toads have been variously regarded as the same species, subspecies of the same species and as separate species.

And to add another layer of complexity....in East Texas this species can be difficult to separate (visually) from the American Toad (A. americanus) population that lives there.

There is a good summary of the changing and historical status of the East Texas Toad taken from Michael Lannoo's account on Amphibiaweb here.

For my purposes here, I just have a recording of one of these toads from eastern Texas. You can decide what to call it yourself!

East Texas (Fowler's) Toad
Tyler County, Texas

East Texas (Fowler's) Toad
Cherokee County, Texas

Here is the recording of the toad from Cherokee County in the picture above. (There is a Gray Treefrog calling in the background)

And here is a recording of a Fowler's Toad from Little Rock, Arkansas.

They sure sound the same to my ear!

© Chris Harrison 2015

Fowler's Toad
Anaxyrus fowleri

Fowler's Toad (Anaxyrus fowleri) has had a confusing taxonomic history. It started off as a small toad that only occurred in the northeast US. However it was soon realized that it occurred over a wide arear of the eastern US. Its identifty was confused because of its overall similarity to the more western Woodhouse's Toad. It has been regarded as its own species, Anaxyrus fowleri, and as a subspecies of Woodhouse's Toad, Anaxyrus woodhousei fowleri. For our discussion here, I regard them as a separate species, Fowler's Toad.

This is a small toad of the eastern woodland areas from the New England area, across the Mississippi valley and down to eastern Oklahoma and East Texas. It's identity in East Texas has been questioned. See my post about the East Texas Toad here. It does not occur in the far southeastern US. There is an approximate range map from Amphibiaweb.org here.

Here is its range in East Texas (from the North American Amphibian Atlas)

Here is the documented/presumed range of the Fowler's and Woodhouse's Toads in Texas. Their zone of contact/overlap is not well documented. As you can see, historical records have the two species coming together somewhere in East Central Texas, but exactly where this boundary lies is not well resolved. This is complicated by the fact that Woodhouse's Toad populations in most of this part of the state have apparently disappeared and they are very rarely found in these areas anymore.

To further add to the confusion, Fowler's Toad appears to interbreed with Woodhouse's Toad at the western edge of its range, Southern Toads (A. terrestris) at the southeastern edge of its range, and American Toads (A. americanus) at various places in its range.

All the taxonomic issues aside, here is a Fowler's Toad calling in Little Rock, Arkansas.

Fowler's Toad
Pulaski County, Arkansas

The call of Fowler's Toad is a typical toad-like trill, but with a buzzy quality.

Looking at the spectrogram for one trill of this call, it is a typical toad-like trill although it has a "buzzier" insect-like quality to it. The carrier frequency of this call is approximately 1.93 Khz.

So in spite of all the taxonomic confusion, these little "forest toads" of the eastern US persist, even if we don't know exactly what they are all the time.

Cajun Chorus Frog
Pseudacris fouquettei

The Cajun Chorus Frog (Pseudacris fouquettei) is a small chorus frog found in the forests and grasslands from the approximately Mississippi River west to east-central Texas then north from the gulf coast to Arkansas and Oklahoma.

Historically this frog has been known as the Western Chorus Frog (Pseudacris triseriata - a reference to the three stripes usually seen on the body) or the Upland Chorus Frog (Pseudacris feriarum). Recent molecular evidence suggests that the population west of the Mississippi in OK, AR, LA, and east TX represents a unique species, P. fouquettei.

Although many Cajun Chorus Frogs have three stripes, some individuals can have only faint indications of those stripes. Here's one from Colorado County, Texas with only faint stripes.

and an individual from Cherokee County, Texas with fairly muted pattern.

Like many of the Chorus Frogs, Cajun Chorus Frogs call from flooded grassy areas or the edge of grassy ponds. They often call from deep within clumps of grass and can be difficult to find while calling. One thing that can give them away is the movement and reflection off their vocal sac as they make their call.

Like many of the chorus frog species, the call of the Cajun Chorus frog is an ascending trill that sounds a bit like someone running their fingernail along the teeth of a plastic comb. Here is a couple of males from a Arkansas on a cool spring night.

As the temperature increases, the rate of their call speeds up. Here is a small group from Colorado County, Texas on a somewhat warmer night (the metallic chip is a bird).

Here is a Cajun Chorus Frog calling from a roadside ditch in Colorado County, Texas on a warm January night -

Bird-voiced Treefrog
Hyla avivoca

The Bird-voiced Treefrog (Hyla avivoca) is a small treefrog of the southern United States. This species has a rather unusual distribution in that it occurs on the east side of the Mississippi River from southern Illinois down to the gulf coast. Along the Gulf Coast it occurs east to the Florida Panhandle and a small area of southern Georgia and barely across into a small area in South Carolina.
West of the Mississippi River, its range is more disjunct with isolated populations in a few areas of Louisiana and southern Arkansas and even the southeast corner of Oklahoma.

Its color pattern is very similar to the slightly larger Gray Treefrogs (Hyla versicolor and Hyla chrysoscelis) with which it shares its range. Like the Gray Treefrogs, the Bird-voiced Treefrog can vary in color from gray to green to even gold in background color, normally broken up with a mottled pattern on the back and legs. They typically have a white (or light) blotch below the eye although this characteristic is also shared with the Gray Treefrog species.

Hyla avivoca
Barnwell County, South Carolina

Hyla avivoca
Ouachita County, Arkansas

It can be separated from the two Gray Treefrog species by lacking the bright orange coloration of the posterior part of the thigh seen in those species.

Hyla avivoca
Barnwell County, South Carolina

As both the common name and scientific name imply, the call of the Bird-voiced Treefrog is a prolonged series of "bird-like" whistles.

Hyla avivoca
Ouachita County, Arkansas

Here is the call of a Bird-voiced Treefrog from Ouachita County, Arkansas in May 2015:

Although their typical call is a long series of whistles as heard above, when we heard them calling that night in Arkansas they occasionally made a shorter call that appeared to be some sort of territorial call between males?

Eastern Narrow-mouthed Toad
Gastrophryne carolinensis

The little Eastern Narrow-mouthed Toad (Gastrophryne carolinensis) is a small pointy-nosed frog of the southeastern United States. It occurs from the east half of Texas up through eastern Oklahoma and then across through southern Missouri, Kentucky, and Virginia and south to the tip of Florida. They are found in swamps, pine forests, wooded clearings, agricultural land or anywhere else there is moisture. They typically spend most of their time under debris (logs, rocks) or underground in burrows where they can remain moist. They only appear on the surface after heavy rains.

Like their western cousins, the Great Plains Narrow-mouthed Toad (G. olivacea), the Eastern Narrow-mouthed Toad will call and breed in any shallow temporary water or the grassy edges of larger water bodies, particularly after heavy rains. The night I made some of these recordings in Arkansas, I recorded a large number of these calling from the flooded grassy edge of a large lake and others calling from a flooded grassy ditch a few feet across with just a few inches of water next to the road. The one thing Narrow-mouthed Toads seem to require for calling and breeding is shallow grassy water edges.

Like the other North American members of the family Microhylidae, these are small, chubby, pointy-nosed little frogs. Like their Great Plains cousins, they also frequently show a fold of skin across the back of the nape.

The Eastern Narrow-mouthed Toad usually has a more prominent pattern than its western congener although this can vary. The distinguishing character separating these two species is the patterns of their underside. While the Great Plains Narrow-mouthed Toad has a generally unmarked, whitish or cream colored belly, the Eastern has a belly that is profusely mottled with black and white. To me it generally appears black with whitish flecking. You can see the belly pattern on the lower sides of the two G. carolinensis pictured here (and in the first picture).

The call of the Eastern Narrow-mouthed Toad is very similar to that of the Great Plains Narrow-mouthed Toad. Both species have a long nasal "bleat" that is somewhat sheep-like. To my ear, the Eastern Narrow-mouthed Toad is a nasal "maaaah" or even"baaah" sound. (I will put together a separate post comparing the two with each other and the related Sheep Frog.)

Narrow-mouthed Toads can be difficult to find while they are calling because they usually call from dense grassy flooded areas, often right within clumps of grass. Even when they are in the open, the often call with just the tips of their noses sticking above the water, like this individual picture below. When you add that calling behavior to the fact that males are often less than an inch in length, they can be tough critters to spot while calling.

Here is the call of a group of three Eastern Narrow-mouthed Toads from Ouachita County, Arkansas, including the one pictured above. (The dry trills of the Cope's Gray Treefrog Hyla chrysoscelis are heard in the background.)

The spectrogram of the loudest of those three calls shows a complex buzzy call typical of this genus. This spectrogram includes two overlapping calls.

In another post, I will compare the calls of this Eastern and Great Plains Narrow-mouthed Toads.

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Bronze Frog
Lithobates clamitans

The Bronze Frog is actually the southern subspecies of the widespread Green Frog (Lithobates clamitans). In the northern parts of its range, the species is a bright green color but as you move south they become more and more brown in color. In the southeastern US they are largely bronzy brown in color.

Here is a pair from the same pond in Little Rock, Arkansas. You can see the varying amounts of green present. The male (with the large tympanic membrane) has some green on his face while the female (smaller tympanic membrane) has very little. This characteristic is variable but as you go north, the frogs get greener.

The call of Lithobates clamitans has been described as being like the "pluck of a banjo string". While this may be an apt description, it isn't a sound that many people are familiar with. However, it is probably the best description I have. To my ear, thesound is a percussive "dunk" or sometimes a double "dunk dunk" with the second "dunk" sounding like an echo of the first. The two part call sounds a bit like the phrase "Dont, do" to me.

Bronze Frogs will often call sporadically from the side of a pond any time of the day. I have also found them to be quite shy and will often not call when you are standing near them. To get this recording is of a Bronze Frog from Little Rock, Arkansas, I found one sitting on the bank of a lake and set the microphone down near it and walked away. After 5 minutes, I can back and had three recordings from the whole time period. I have compressed them here so you can here them without having to hear the other 5 minutes of silence!

Here is a recording of a group of Bronze Frogs calling from a bottomland hardwood pond in the early afternoon after a brief rain shower.

Although the previous recordings have Bronze Frogs singing a single "pluck" note, many times when they are calling in a small group or alone you get a two note call. See if you agree it sounds like they are saying "Dont, Do" -

Here's the spectrograph of one of those "Don't, Do" calls -

I did finally get a recording of this species in Texas. Here's a single individual calling in Cherokee County (along with Gray Treefrogs, Cope's Gray Treefrogs, Blanchard's Cricket Frogs, Southern Leopard Frogs, and some distant "East Texas" Toads) -

and another chorus from deep Southeast Texas in Orange County -

and here's a short video clip of a Bronze Frog calling from some floating vegetation on a roadside ditch near Humanoke, Arkansas. -

Once again this represents a compressed version of what the call was really like. These 30 seconds worth of calls were trimmed out of over 5 minutes of video. Most of the time he sat silent!

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© Chris Harrison 2015 & 2017

The Gray Treefrogs revisited
Hyla versicolor vs. Hyla chrysoscelis

I have several blog entries here discussing the two species of Gray Treefrogs (Hyla versicolor vs. Hyla chrysoscelis). I won't go into all the details again here, but I just wanted to post a neat recording I got the other night.

I have been recording Gray Treefrogs in and around Central Texas for several years trying to define the boundaries of their contact. One thing I hoped to get was a recording of both species calling together. Fortunately, in May of 2015, I finally got that recording.

In this short excerpt, you hear one Hyla versicolor call followed by a single Hyla chrysoscelis call. You can hear how much drier and more buzzy the H. chrysoscelis call is than the bird-like nature of the H. versicolor call.

Two Gray Treefrog calls - Hyla versicolor then Hyla chrysocelis mp3

This difference is due to the speed of the trill. The slower the trill-rate the more "bird-like" it is and the faster the trill the more "buzzy" it is.

If you look at the spectrogram for these two calls you can see the difference in the number of pulses per second.

The first call is the H. versicolor call followed by the H. chrysoscelis call. This is a direct sample from recording in the field where both species were calling together at the same pond at the same time.

Looking at the spectrogram, we can measure the number of individual pulses per unit time for each frog. The first call (Hyla versicolor) consists of 13 pulses and takes 0.41 seconds. That is a pulse frequency of 31.7 pulses per second.

The second call (Hyla versicolor) consists of 25 pulses in 0.42 seconds for a pulse frequency of 59.5 pulses per second.

Of course, you couldn't count 59.5 pulses per second in the field, but the ear can hear the difference with some training.

Although the pulse rate of both species can vary with temperature, these two frogs were at the same temperature because they were recorded at the same pond at the same time.

I have subsequently added a longer comparison call series to my original Gray Treefrogs post.

Central Texas Leopard Frogs
Lithobates sphenocephalus vs. Lithobates berlandieri

In the area where I live, Central Texas, there are two very similar species of Leopard Frogs. The Rio Grande Leopard Frog (Lithobates berlandieri) is a frog of the southern and western parts of the Lone Star State. The Southern Leopard Frog (Lithobates sphenocephalus) on the other hand is a Leopard Frog of the southeastern United States whose range runs into the central part of Texas. A third species, the Plains Leopard Frog (Lithobates blairi) occurs in the prairie parts of the panhandle down into the southern plains of north-central Texas, but is outside the area discussed here.

The problem is that all Leopard Frogs pretty much look the same. In fact, originally all the Leopard Frogs in North America were known as a single species, Lithobates (Rana) pipiens until biologists discovered that there were several species in this group.

Here is a photo of a Rio Grande Leopard Frog (L. berlandieri)

and here is a photo of a Southern Leopard Frog (Lithobates sphenocephalus).

In looking at the two photos you can see that both species are spotted, "typical" frogs with pointed noses and a dorsolateral fold (raised ridge) running down each side of the back from behind the eye all the way down to the back end of the body. The ridge stands out because it is raised and usually lighter in color (gold, white) than the rest of the body.

The body color varies in both species, although the Southern Leopard Frog is usually more green than the Rio Grande Leopard Frog. But, either species can be green or brown or even grayish with darker spots. The density of spots varies as well as you can see comparing the two individuals in the above photos. The shape of the spots varies as well, but either species can have round spots or square spots or anything in between.

One physical character that can be useful in distinguishing them is this dorsolateral fold. If you notice in the top photo, the dorsolateral fold is disrupted back by the hind legs and moved in a little towards the back.

Trying to show that on a computer screen can be tough, but I will try to "draw" it as follows. The following paired vertical lines represent the dorsolateral folds starting at the eyes for each species (the proportional font makes the southern's fold wavy in my drawing, but it is straighter on a real frog).

Rio Grande Southern

| | starting behind eye | |

| | | |
| | | |
| | | |
| | | |
| | near back legs | |
| | | |

The point is to see how the dorsolateral folds are "inset" near the hind legs in L. berlandieri but straight in L. sphenocephalus. Having said that, I find this character to be less than 100% obvious in some animals.

Here's a few photos to show how much they can vary in color and spot pattern.

Rio Grande Leopard Frogs (L. berlandieri)

and a selection of Southern Leopard Frogs (L. sphenocephalus):

Another way to distinguish them in the field is by their mating calls. The call of the Rio Grande Leopard Frog (L. berlandieri) sounds like a short "snore". The snore is generally repeated twice or even three times. Occasionally you hear sort of a "whimper" mixed in among the snores as in this recording.
Here is a group of calling Rio Grande Leopard Frogs from Kinney County, Texas in June 2014.

In contrast, the call of the Southern Leopard Frog (L. sphenocephalus) is more of a chuckling sound than a snoring sound. They also make a sound a bit like a finger being rubbed over a balloon, but the Rio Grande Leopard Frog sometimes makes that sound as well (i.e. the "whimper in the previous recording). The higher pitched chuckles are diagnostic for the Southern Leopard Frog in our area. This group of Southern Leopard Frogs was recorded on Aransas National Wildlife Refuge in March 2014.

In December 2016, I recorded some Rio Grande Leopard Frogs north of Hondo, Texas at a lower temperature than I had normally heard them calling. It was only 56 degrees but had rained heavily so they were calling at this shallow roadside pond (where I had recorded them several times before). However, due to the low temperature, their "snores" were much slower and the calls were remniscent of those of the Southern Leopard Frog.

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After recording many hundreds Leopard Frog calls around the San Antonio area over the last five years, I have found an an apparent pattern to their distribution. Effectively, north of San Antonio, I-35 (the balcones escarpment) seems to separate the two species while south-east of San Antonio, the San Antonio River tends to separate the species. The Southern Leopard Frog is found east of the Balcones Escarpment and north of the San Antonio River while the Rio Grande Leopard Frog starts south and west of the San Antonio River and the Balcones Escarpment. This is hardly the definitive range map, but I have yet to find the "wrong" species on the wrong side of these hypothetical boundaries. {NB: I have subsequently recorded the Rio Grande Leopard Frog on the northern side of the San Antonio River, but only a few miles north).

I have not recorded north of Austin to know what happens to the boundary when you start to include Lithobates blairi in the mix.

When I look at the range maps in field guides I see a large area of overlap of the two species, which I haven't observed. I'm not sure what to make of that discrepancy other than to keep searching for Southerns west of the line and Rio Grandes north and east of the "boundary".

Here's a map of the places I have recorded calls of the two species. B pins represent localities for Rio Grande (berlandieri) while the S pins represent localities for Southern (sphenocephalus) Leopard Frogs:

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