Just got back from a trip to Belize where I had hoped to add a couple of species to my lifelist since it was the beginning of the wet season. The purpose of the trip was to visit a friend who lived there, not frog recording, but I always have my gear with me!
Unfortunately, we were staying in an area of mangrove lowland swamps and the mosquitos were so oppressive, we didn't get out much at night to listen to frogs. I never even heard any new species. 😭
But all of those species were ones I had seen/heard/recorded before. I needed a better recording of the Trachycephalus, but the time I tried to get them, they shut up and the mosquitos drove me back to the porch.
The locals said this was the worst time of year for mosquitos. The first few rains of the season cause a massive mosquito hatch and either two weeks earlier and a few weeks later they are better.
We did travel inland to some rainforest and marsh areas and the mosquitos weren't nearly as bad, but we didn't hear any frogs there.
So here's my few recordings as proof I've been to Belize!
The Veined Treefrog (Trachycephalus vermiculatus) is a large species of neotropical treefrog found from central Mexico down to the central regions of South America. They are large frogs often with very beautiful patterns. Interestingly, like all members of the genus Trachycephalus, this species of frog has green bones.
If you are looking in a field guide for Mexico or Central America, you might see this same species under the scientific name Phrynohyas venulosus or Trachycephalus venulosus or Trachycephalus typhonius. Those had been their scientific names throughout their taxonomic history until a recent revision of the typhonius group showed that the name this northern population wasits own species and the name vermiculatus pre-dated the name venulosus. Therefore under the rules of taxonomic nomenclature Trachycephalus vermiculatus had precedence.
However, this group of frogs is still a mess. Some authorities still say all the Mexican, Central American and Guinanan shield populations belong in T. typhonius. And regardless of the correct name, this "species" is probably a group of species all lumped together. The "real" T. vermiculatus (or typhonius?) is probably restricted to the Guianan shield in South America, so these Mexican species are probably something different? And then there is the issue of there being an isolated population on the West Coast of Mexico that may not be the same species as the Yucatecan form I am discussing. . Confused? How about we just call them Veined Treefrogs?
Here's a range map from iNaturalist showing the "whole species" range.
The old specific epithet "venulosus" is a reference to the numerous glands on the frog's back from which it secretes a sticky white toxin when disturbed. Lots of frog species secrete similar toxins, but the Veined Treefrog has taken this skill to a whole new level. Just handling one for a few seconds can leave your hands gummed up for hours. It must take a very persistent predator to swallow one of these sticky frogs. This ability has given some of the South American relatives of this frog the name "Milk Frog". Here's what my hands looked like after holding one of these frogs for just a few seconds!
I have seen this species of frog many times in the past, but only once have I had my recording gear with me while they were calling. And I didn't get a very good recording so I decided not to upload that one to iNaturalist until I got a better one. That was 8 years ago. I decided that I might as well upload this species now in the hope that this would give me a chance to get better recordings this year when I travel to Belize. As a lifelong birder, I know the old adage that the first one is the hardest one to get. Once you see the first one of any species, you will start seeing them everywhere. 😏
So this recording was made in June of 2017 in on the northern boundaries of the Calakmul Biosphere Reserve, Campeche, Yucatan. It had rained very hard in this area earlier in the day and lots of frog species were calling. I pointed my microphone out into the marshes and recorded many species, including a distant chorus of Veined Treefrogs. I have brought out the Veined Treefrogs in this recording and reduced the gain for all the other species.
The call of this species is a deep "roon". It is remniscent of the call of the American Bullfrog and a large chorus of these Veined Treefrogs does sound a bit like that species. The two species do not overlap in range though.
The other species heard in this recording include Stauffer's Treefrog, Mexican Treefrog and the Sheep Frog.
Australia has several species of small grassland frogs called Sedge Frogs. They are sometimes called Dwarf Treefrogs but I think the name Sedge Frog is more descriptive of their grassy habitats. All the Sedge Frog species are small green frogs with a brownish border running from their nose through their eye towards the rear of their body. They can be green or tan, with or without a brown stripe down the back.
Northern Sedge Frog (L. bicolor) from Fogg Dam in the Northern Territory In this case, this frog can be identified by range.
Sedge Frog (Litoria cf. bicolor) from NE Queensland. Although this best matches descriptions of L. bicolor, it is difficult to be certain.
Eastern Sedge Frog (Litoria fallax) from NE Queensland. In this case, the species identity could be confirmed by call.
The Eastern Sedge Frog (Litoria fallax) is found along the east coast of Australia from the tropics near Cooktown south to Victoria. The Northern Sedge Frog (L. bicolor) is found from tropical NE Queensland across the northern part of the country to Kimberley Region of Western Australia. On the map below, the Eastern Sedge Frog is represented by the golden color, the Northern Sedge Frog by the teal color and you can see their area of overlap in NE Queensland by the lighter blue region. This is where I ran into trouble with the two species.
Range maps for Litoria bicolor (teal) and Litoria fallax (gold) showing region of overlap. Shape files downloaded from the IUCN Red Book and overlayed onto Google Earth
While trying to identify frogs in that overlap area, I found myself struggling to distinguish between these two species. They can be green or tan, with or without a brown stripe down the back. Field guides say that they can be distinguised sometimes by the fact that L. bicolor more often has a dark stripe down its back, but both
species can show that character. Supposedly the dark stripe on the Northern Sedge Frog (L. bicolor) goes further back onto the "tail", whereas it tends to fade on the Eastern Sedge Frog (L. fallax).
Now obviously if you've read any of the other "similar species" comparisons I have on my blog, you would expect me to say, "but fortunately, their calls are very different and easy to distinguish". But in this case that isn't true. Their calls are different and can be distinguished but the difference is more subtle and can be hard to discern when listening to a chorus.
Both species have a call that consists of one or two "chuck" sounds and an upward slurred raspy trill. The trill sounds like a fingernail over a very delicate comb.
Here's the Eastern Sedge Frog's (L. fallax) call -
The difference lies in the order of the "chucks" and "trills". Although both species make one or two "chucks" and a trill, the order is different. The Eastern (fallax) makes a trill followed by one or two "chucks". The Northern (bicolor) does the opposite, a trill followed a "chuck" or two.
So the Eastern Sedge Frog calls trill-chuck-chuck (or trill-chuck).
The Northern Sedge Frog calls chuck-chuck-trill (or chuck-trill).
The tricky part is if you are listening to a big chorus, it can be hard to figure out who is starting where?!
Listen to this group and see if you can tell if it is chuck-chuck-trill or trill-chuck-chuck?
How about this one?
The first recording was Northern, the second recording was Eastern. Simple, right? 😆
Here's a visual showing the two species on a spectrogram. You can see the different arrangement of chucks and trills. Ignore the differences in frequency (pitch). That is temperature dependent, not species dependent. They were recorded at different times (years!) in different places with different recorders and microphones.
I had the hardest time telling these things apart in NE Queensland until I heard what could only be Northerns in the Northern Territory. Once I heard their calls, I understood and could hear the difference.
Now I want to go back to NE Queensland to try and hear them again. Who am I kidding? Any trip to NE Queensland for any reason would be fine. 😉
The Yellow-flecked Grassfrog (Sachatamia albomaculata) is a delicate glassfrog species found in lowland wet forests of Central America. From maps I have seen, it has an rather discontinuous range Northern Honduras south through Costa Rica and Panama into western Colombia, but then also shows up again in Ecuador. This may represent more of a lack of data than the true range of the species.
Map derived from range map on iNaturalist.org
This was another bonus frog species I recorded accidentally. I had seen it before on an earlier trip to Panama, but not heard it. In January 2025, I was trying to record some Red-webbed Treefrogs and Harlequin Treefrogs around the pond on our hotel grounds. When I posted those recordings to iNaturalist, neotropical frog expert and iNat user ibanezr confirmed my IDs, but added that he could hear Sachatamia albomaculata in the recording as well.
This led me down a rabbit hole to try to find what this species sounds like and then isolate it from any of my recordings.
The call of this species is a high pitched peep or tick with a dominant frequency ~6600 Hz. Because of its high pitch I probably dismissed it as an insect in my original recordings. (This recording is filtered and edited to remove some of the other distracting species of frogs heard calling.)
Although I got a number of new frog species for my recording list while in Panama last summer, there were a couple of species I saw but didn't get to record. Fortunately, I spent December-January there again and although it was the beginning of the dry season, we had enough rain to get a total of 9 species recorded including one new one.
The Pug-nosed Treefrog (Smilisca sila) is a drab, somewhat smaller species of Smilisca found from the Pacific Coast of Costa Rica down through the central parts of Panama and into the lowlands of Colombia. This is a species found along rocky streams within its range.
These frogs are generally tan with varying amounts of green flecking or spotting on the dorsum. Their skin under their hindlimbs and on their toe webbing is suffused with blue. This species gets its common name for its relatively shorter face compared to the other Smilisca species. These frogs were recorded calling from rocks alongside a stream in a premontane forest.
The call of this species is a coarse quacking sound. It is somewhat remniscent of the larger Smilisca species, although not quite as loud nor complex as their calls.
The calls seem to change as they are repeated. When you look at the spectrogram from the last part (last four calls) of that recording, you can see how the call seems to get more "complicated" as it progresses. The first calls are very short compressed "quacks" but later calls are slowed down into longer rattling sounds.
Here's a small chorus of Pug-nosed Treefrogs from along the same stream -
Spent a couple of weeks in Panama during the summer of 2024. I went on the Canopy Family Herpetology at the Isthmus tour, which was great.
Of the 37 species of anurans we encountered, I was able to record at least 24 species. Of those, at least 15 species were new to my recording lifelist including:
Boana platanera photo by Mateo Garcia Mejía Used under Creative Commons license granted in this iNaturalist record
A big part of the adventure of making this blog and recording frog calls and putting together this blog is trying to identify the various frog sounds I capture. In the United States this is a pretty easy task because I know many of the calls from experience and those that I don't are readily found described in field guides and recorded online in various places.
But outside the US and Australia, it isn't as easy. Although the calls for many species are known and described in field guides or at least the scientific literature, actually getting the opportunity to hear what the call sounds like are few and far between. And for many species, the calls have never been documented. So it can take me months of reading, listening online and other detective work to ID some of my recordings (I have dozens of calls I still don't know as well!).
This recording was part of an all night recording I made at a pond at the edge of the Piedras Blancas National Park in southern Costa Rica.
After I made this recording, I was a bit confused as to the identity of this frog. I knew it didn't sound like the locally common Boana rosenbergi and I couldn't figure out what other species could sound like this. So I did some searching using online sources like xeno-canto.org, iNaturalist.org, Fonozoo.com and found the most similar call I could and that was a recording of the Emerald-eyed Treefrog (Boana crepitans).
But Boana crepitans doesn't occur in Central America; it is restricted to the Atlantic Coast of Brazil. So that led me to a taxonomic hunt using Amphibian Species of the World to find what the closest relative to B. crepitans would be in Costa Rica. That led me to Boana xerophylla which eventually led me to this paper which described a new species, Boana platanera, based on specimens from the northern part of the range of B. xerophylla.
Unfortunately, that paper described the new species as occurring in Trinidad and
Tobago, Venezuela (north of the Orinoco River), northwestern Colombia
and into Central Panama. But the species did not make it into Costa Rica. iNaturalist had this record from David in northern Panama which is only 50 miles from where my recording was made (although some have questioned that ID).
Here is a map taken from iNaturalist.org showing the approximate range (pink polygon) and iNaturalist records (red squares). Obviously the species is documented from outside the range shown on the iNaturalist map. The map on the IUCN Red List is more broad, but still terminates in Central Panama. This recording was made at the location indicated by the red square identified by the black arrow on this map above. It is the first record for Costa Rica, although barely into Costa Rica.
So I had to dive into the description paper to see if this could be the species in question. Fortunately, the paper had descriptions of the call and waveform diagrams and these matched my recording almost perfectly based
I have subsquently listened to all the available recordings for this species on iNaturalist and they sound similar enough to confirm my identification (to me?). I can not find another species that could make a similar call that is in range.
Escalona Sulbarán, M., E. La Marca, M. C. Castellanos-Montero, A.
Fouquet, A. J. Crawford, F. J. M. Rojas-Runjaic, A. A. Giaretta, J. C.
Señaris, and S. Castroviejo-Fisher. 2021. Integrative taxonomy reveals a
new but common Neotropical treefrog, hidden under the name Boana xerophylla. Zootaxa 4981: 401–448 (https://doi.org/10.11646/zootaxa.4981.3.1).
I love microhylid frogs. There's just something about their chubby little bodies and pointy noses that I find cute. And then our US species have wonderful, loud sheep-like bleating calls. So I've always wanted to see and here some of the neotropical microhylids but had always come up short in my travels. So I was excited on my Panama trip to get an opportunity to add a new genus of microhylid to my recording list.
The Panamanian Humming Frog (Elachistocleis panamensis) is an odd, pointy-nosed microhylid that occurs from central Panama into the lowlands of Colombia and Venezuela. It is related to our North American Narrow-mouthed Toads (Gastrophryne sp.).
range map derived from iNaturalist.org (2024)
They are generally dark with a brownish-yellow back and an irregular, dark mid-dorsal stripe. The mid-dorsal stripe is split by a thin yellow line from the tip of the pointy nose to the end of the body.
The common name "humming frog" is derived from the calls of other members of this genus in South America whose calls I guess could be considered reminiscent of a humming sound, at least from a distance.
But this northernmost representative of the genus has a completely different type of call. The call of the Panamanian Humming Frog is more of a high-pitched whistled trilling sound. It reminds me somewhat of the high-pitched trill of the Australian Rain Frog (Austrochaperina pluvialis)
I heard these frogs calling from a flooded grassy ditch after some heavy rains in the Tocumen marshes of Central Panama. The call of this species is fairly high pitched for a frog. Because of the high pitch of this trill, I assumed it was an insect until I got home and did some research. (The sharp "chick" calls you hear among the Humming Frog calls are part of the call of the Túngara Frog. I filtered out the descending parts of the call to bring out the Humming Frog.)
You can see in this spectrogram how there are 12 rapid high-pitched (5 kHz) chirps in less than half a second.
So once again, I got a recording lifer by just point my microphone at an interesting sound in a marsh and then doing some research later to find out I had added a new recording lifer to my list! Always a good day when I can do that! ___________________
The Panamanian Granular Toad (Rhinella centralis) is a small flat-headed toad restricted to Panama. It used to be considered the same species with the widespread South American Granular Toad (R. granulosus) but it was elevated to its own species in 2009.
Range map from iNaturalist.org (2024)
When I read about these toads and saw pictures of them, for some reason I thought they would be medium to large sized toads since many Rhinella species are very large. I was rather surprised when I found these toads along a dirt road through the Tocumen Marshes in Central Panama just how small they were.
The call of this species is exactly what I would expect for a toad of this size, a high pitched trill. The trill lasts around 3-4 seconds and with a carrier frequency (dominant pitch) of around 2.5kHz. In general pitch, it reminded me of the call of the North American Red-spotted Toad (Anaxyrus punctatus), a similarly sized toad, although that species has a longer trill.
Here's a couple of Panamanian Granular Toads calling next to each other in the Tocumen Marshes -
As so often happens when you are trying to record one species of frog, another species right next to it pipes in and makes it hard to get the recording of your target species. That's what happened in this recording. I was trying to record a Colombian Four-eyed Frog (Pleurodema brachyops - the hollow "ponk, ponk") when a couple of Panamanian Granular Toads started calling right next to them, and then a Tungara Frog (Engystomops pustulosus) added its "toy ray gun" "PEUW" song to ruin my recording.
The Colombian Four-eyed Frog (Pleurodema brachyops) is a small chubby "toad-like" frog found from Central Panama down into Colombia, Venezuela and across the northern part of the Guyanan Shield.
range map derived from iNaturalist.org (2024)
Although they look somewhat similar to the Spadefoots of North America, they are actually more closely related to the widespread South and Central American "White-lipped Frogs" (Leptodactylidae).
They get their common name four-eyed from from an unusual defensive behavior. When threatened, they point their broad nose down, raising their hind legs and show enlarged "eye-spots" on the rear of their torso to the prospective predator. It is assumed the eye spots contrasting with the bright red thighs attract the attention of a predator, making the predator think they are a much larger animal. Here's a photo of the posterior side of a calling frog showing the contrasting dark spots on the rear of the body.
As I was trying to record this Four-eyed Frog calling, a couple of other species were calling next to it making it hard to isolate the target species. You can hear the honking of the four-eyed frogs along with the "ray-gun peuw" calls of the Tungara Frog (Engystomops pustulosus) and the loud trill of the Panamanian Granular Toad (Rhinella centralis).
