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Herping Finds

March 17, 2019

On a rare clear night in the cloud forest during the rainy season, our local herpetologist, Eric Osterman, and I decided to go out for a night walk. We estimated that we had anywhere between a few minutes and a few hours before the rain would start again, so we quickly scrambled up the Bosque Trail into the vast primary forest. As Eric informed me, the best time to see amphibians and reptiles in the cloud forest is right after a hard rain, and right before the inevitable next rain showers. While frogs and some reptiles are asleep, they purposefully position themselves on leaves to sense vibrations of potential predators scrambling up the stems of the plants they are situated upon. Raindrops falling onto leaves mimic these vibrations, forcing these species to find new hiding places.
On this particular night, I was on the lookout to see more species of rainfrogs. Rainfrogs are found in southern Central America and northern South America and are especially common in the Andean foothills of Ecuador, Colombia, and Peru. These frogs are unique because they have incomplete metamorphosis; they grow directly from eggs into adults. The genus that encompasses all rainfrog species, Pristimantis, is believed to be the largest genus of vertebrates with over 400 species identified and counting. Not only are their songs peaceful in the evenings, but each species is so unique that once you find one, you cannot stop looking for more!
Eric and I were in luck! We chose the perfect evening to see four species of Pristimantis. We saw the yellow-groin rainfrog (Pristimantis luteolateralis), Pasture’s rainfrog (Pristimantis achatinus), red-groin rainfrog (Pristimantis verecundus), and my personal favorite, the blue-thighed rainfrog (Pristimantis crucifer). This species is categorized as Vulnerable on the IUCN Red List, and we found five individuals along the property, a good sign that the habitat being preserved is conducive to the success of the species. The blue-thighed rainfrog is easily identified by blue marks along the inside of the thighs. At first glance, this frog looks bumpy and rough to the touch, but if it is touched by a potential predator, its skin changes to a smooth texture to facilitate an easy escape. I bore witness to this process, and indeed the frog easily slipped out of my hand!
At the end of February, herpetologists released a paper describing a new species of glassfrog, Nymphargus manduriacu, roughly 40 kilometers north of Reserva Las Tangaras. This species was discovered at population levels so low that it is already characterized as Critically Endangered by the IUCN. Nymphargus manduriacu was encountered on an ecological reserve similar to Reserva Las Tangaras and therefore sheds light on the importance of dedicating land to conservation.


Link to the publication on Nymphargus manduriacu can be found at:

More information about the IUCN Red List can be found here:

More information on Eric Osterman and his great herping skills can be found at:

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