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Cruziohyla calcarifer – closing the circle

Over three years have passed since my unforgettable encounter with the fringe tree frog, Cruziohyla craspedopus, in the Amazon rainforest of Ecuador. That experience is still one of my all-time favorite moments of working in the field. Since then, I learned a lot about this species and nowadays I see them every time I visit Ecuador (as you can probably tell by their growing presence in my frogs gallery). Still, even after all this time the fringe tree frog remains high up on my list of the world’s most beautiful tree frogs. But it felt like something was missing. I decided to take a trip to Costa Rica, and right from the start I had one goal in mind: to find the other half of genus Cruziohyla – the splendid leaf frog, Cruziohyla calcarifer.

Splendid leaf frog (Cruziohyla calcarifer)

Splendid leaf frog (Cruziohyla calcarifer)

After researching a little on C. calcarifer’s distribution, I decided to contact the place that in my mind packed the best potential of seeing one. The Costa Rican Amphibian Research Center (neatly abbreviated C.R.A.R.C.!) is a small biological research station located close to the Siquirres River in the Guayacán rainforest reserve, in Limón Province. It is owned and run by Brian Kubicki, a conservation naturalist who dedicated his life to the study of Costa Rican amphibians, with special focus on glass frogs, poison frogs, tree frogs and lungless salamanders. I thought if there is one person that can help me find C. calcarifer in Costa Rica, it must be him. Remember the frog poster from 2003 that I mentioned in the beginning of my post about C. craspedopus? Brian Kubicki was the person signed at the bottom of that poster. Now how cool is that.

To begin with, the C.R.A.R.C. Guayacán reserve is stunning. There are many interesting corners with different types of microhabitats, so a huge potential for finding interesting reptiles and amphibians, not to mention arthropods. Unfortunately for me, I arrived to the reserve during a dry spell, as it has not rained for days prior my arrival, and most habitats that were not directly connected to natural springs or the river were fairly dry. Even so, I still found the place highly biodiveresed, and recorded many interesting species of arthropods, some of which I have not yet had the chance to see in the wild.

Alas, I was there to find C. calcarifer, and I was worried that the area might have been too dry. Brain kindly offered to hike with me at night and show me some good spots to find specific amphibians. And it did not take him long; once we hit a certain trail he found C. calcarifer within minutes! What a gorgeous species. I will just paste here my description of C. calcarifer from the post about its sister species:

“…a massive tree frog, with eye-catching coloration: dark green (dorsal) and bright orange (ventral). The sides of its body are finely striped in black against an orange background. Its eyes, featuring a vertical pupil – an indication this animal has a nocturnal lifestyle, are orange with a grey center. In addition, the foot-webbing is wide and the adhesion discs on the fingers are large and round, giving it a cutesy appearance.”

Isn't it gorgeous? It is hard not to fall in love with these tree frogs.

Isn’t it gorgeous? It is hard not to fall in love with these tree frogs.

This tree frog species is indeed, as its common name suggests, splendid. It was exactly what I expected. The frog we found was a female, and I was surprised how robust it was. It is not every day you get to see an amphibian that is both colorful and big.

Cruziohyla calcarifer. So adorable and quite a hefty frog

Cruziohyla calcarifer. So adorable and quite a hefty frog

As mentioned, we found the frog at night. However, I wanted to see if I can locate it myself so I went back to the same spot in the morning. Let me tell you, it was not easy to find it in daylight. Not only it is difficult to find a green frog in the “sea of green” which is the rainforest, but also the tree frog is hunkered down and blends perfectly with the leaf it is resting on. After some time searching I thought about giving up, but then I looked up. I saw the perfect silhouette of a resting frog on one of the palm leaves, backlit by the sunrays penetrating the rainforest canopy. This could have still been an optical illusion created by a fallen leaf casting the silhouette. Yet, it was indeed C. calcarifer. I couldn’t be happier.

Splendid leaf frog (Cruziohyla calcarifer) in its rainforest habitat

Splendid leaf frog (Cruziohyla calcarifer) in its rainforest habitat

Cruziohyla calcarifer is a good climber and spends most of its time in the canopy

Cruziohyla calcarifer is a good climber and spends most of its time in the canopy

Splendid leaf frog (Cruziohyla calcarifer) showing off its beautiful stripy coloration

Splendid leaf frog (Cruziohyla calcarifer) showing off its beautiful stripy coloration

To me, seeing Cruziohyla calcarifer in the wild is a way to close a circle on a journey that started over a decade ago in a backpacker’s hostel in Costa Rica, continued in the Amazon rainforests of Ecuador, and ended in Costa Rica again.

Splendid leaf frog (Cruziohyla calcarifer) and fringe tree frog (Cruziohyla craspedopus). I wish moments like this one were possible in real life. Unfortunately, such a gathering of the two species is impossible. Even though both Cruziohyla species occur in Ecuador, they are separated by the Andes Mountains. C. calcarifer occupies the northwestern slopes, while C. craspedopus is found in Amazonian lowlands on the eastern side.

Splendid leaf frog (Cruziohyla calcarifer) and fringe tree frog (Cruziohyla craspedopus). I wish moments like this one were possible in real life. Unfortunately, such a gathering of the two species is impossible. Even though both Cruziohyla species occur in Ecuador, they are separated by the Andes Mountains. C. calcarifer occupies the northwestern slopes, while C. craspedopus is found in Amazonian lowlands on the eastern side.

Cruziohyla – a dream come true

In 2003 I visited Costa Rica as a part of my first trip to Latin America. One of the hostels I stayed at had a large poster hung featuring many Costa Rican frog species, to show the high amphibian diversity that is found in this beautiful country. This was the first time I saw a photo of a splendid leaf frog, Cruziohyla calcarifer (the same frog appears also on the cover of Piotr Nascrecki’s book “The Smaller Majority”). Back then it was called Agalychnis calcarifer but in 2005, following a revision in the Hylidae family, it was placed within a new genus, Cruziohyla, along with another species.
When I saw the photo I was stunned. It looked like a massive tree frog, with eye-catching coloration: dark green (dorsal) and bright orange (ventral). The sides of its body are finely striped in black against an orange background. Its eyes, featuring a vertical pupil – an indication this animal has a nocturnal lifestyle, are orange with a grey center. In addition, the foot-webbing is wide and the adhesion discs on the fingers are large and round, giving it a cutesy appearance.
I decided to set out and look for this species in the rainforest during my time in Costa Rica. Of course at that time I knew nothing about these frogs, and as expected I failed miserably in finding them (but I did find many red-eyed tree frogs!)

Fast forward to 2014. Visiting the Amazon rainforest in Ecuador, I was mainly searching for interesting insects and arachnids at night. I was fortunate to have good weather throughout this visit, until it started raining heavily on one of the nights prior to my departure. But this rain was like no other I have seen before – it was so warm that a thick fog formed, covering everything in the forest understory. I was about to declare this night a failure for observing arthropods, but very soon I learned my mistake. Following the creation of this natural sauna, hundreds, no, thousands of animals came out of their hiding spots. The forest was buzzing with orthopteran and amphibian calls, roaming arachnids and crawling velvet worms. It was magnificent, a naturalist’s dream. Among the noisy frog chorus coming from the dense canopy, there was one distinct call, louder than the others, which sounded like a short “moo” (remember those tipping-can cow-sound toys? Something like that.) unlike the typical “cluck” call characterizing tree frog species. It wasn’t long before I located the source, and upon seeing it my heart skipped a beat. Sitting on a leaf before me was the second species in the Cruziohyla genus, the fringe tree frog (Cruziohyla craspedopus)!

Fringe tree frog (Cruziohyla craspedopus) in its natural habitat. Photographed in the Amazon rainforest in Ecuador.

Fringe tree frog (Cruziohyla craspedopus) in its natural habitat. Photographed in the Amazon rainforest in Ecuador.

 

This is, in my humble opinion, the most beautiful tree frog in the world. I know that any attempt I make to describe it will not do justice to its astonishing splendor. The general appearance is similar to that of C. calcarifer, but the green dorsum is marbled with small bluish splotches that resemble moss or lichens and blend perfectly with tree leaves in the rainforest. Moreover, the body margins have “fringes” that are exceptionally long on the hind legs. Males sometimes display them to signal other males or females during courtship by extending their legs backwards.

Species of Cruziohyla are characterized by their bicolored iris, which is unique among tree frogs.

Species of Cruziohyla are characterized by their bicolored iris, which is unique among tree frogs.

 

At rest, C. craspedopus conceals its bright colors and blends perfectly with its surroundings thanks to color patches that resemble lichen spots on leaves.

At rest, C. craspedopus conceals its bright colors and blends perfectly with its surroundings thanks to color patches that resemble lichen spots on leaves.

 

A climbing C. craspedopus reveals its aposematic colors that are reminiscent of a tiger: bright orange contrasted with dark stripes. Note the fringes on the hind legs that gave this frog its common name.

A climbing C. craspedopus reveals its aposematic colors that are reminiscent of a tiger: bright orange contrasted with dark stripes. Note the fringes on the hind legs that gave this frog its common name.

 

Being a high canopy frog, C. craspedopus is cryptic and usually difficult to observe. I have never even dreamed I would have the chance of seeing one, let along in the wild. But spending some time walking in the warm fog I managed to see not one, not two but close to ten individuals. It seems that they like these conditions. After learning their favorite resting spots I could easily find them also by day. Fringe tree frogs descend from the high branches solely for breeding. Pairs in amplexus (typical anuran behavior in which the male grasps the female using his front legs and rides on her back) move about in the canopy until they locate a small body of water with an overhead cover, usually under fallen trees. The females then deposit egg clutches hanging above the water, and the hatching tadpoles drop down and start their aquatic life. Even though I checked under many fallen trees (while searching for Amblypygi) I was unsuccessful in finding egg clutches of this species. Better luck next time.

Finding a fringe tree frog during the day is a mission close to impossible. In addition to their excellent camouflage, the frogs tend to rest on tree leaves high above the ground, making it difficult (and dangerous) to access them.

Finding a fringe tree frog during the day is a mission close to impossible. In addition to their excellent camouflage, the frogs tend to rest on tree leaves high above the ground, making it difficult (and dangerous) to access them.

 

Cruziohyla craspedopus, "Meet Your Neighbours" style

Cruziohyla craspedopus, “Meet Your Neighbours” style