Paulo's Favorite Costa Rican Frog
Updated: Feb 4, 2021
Photos by Paulo Valerio and Greg Basco. © Foto Verde Tours
Reticulated Glass Frog (Hyalinobatracium valerioi)
This small glass frog (in the family Centrolenidae) is found in lowland and mid-elevation forests from Costa Rica to Ecuador, usually near clean, fast flowing streams. It is quite uncommon, and being less than one inch in size, is easily overlooked by a casual hiker.
The genus name Hyalinobatrachium means transparent. The species moniker valerioi, first described by Dunn in 1930, is dedicated to my great-grandfather Manuel Valerio, a biologist and director of the National Museum of Costa Rica! Now you can start to understand why it’s my favorite Costa Rican frog :-)
But, family history aside, the Reticulated Glass Frog became one of my favorite frogs since I first found it along a creek near my house in the suburbs of Costa Rica’s capital (things were different then!) when I was 12. There are several aspects of this frog that fascinated me from the start.
First, they are voracious! Despite their tiny size, these creatures are amazing predators, feeding on insects that they actively hunt for, all the way from the rainforest floor to the canopy.
Second, like most glass frogs, the skin of the ventral portion (e.g., the underbelly) is almost transparent, and the internal organs can be easily seen.
And third, the color pattern on the back is amazing – bright yellow-gold circular marks on a regular arrangement set off against darker green skin, forming a web or net-like pattern (hence the name reticulated).
And fourth, and what is most amazing to me, is that this coloration has a lot to do with one of the most remarkable feats on this species – it’s dedication to its kids. Indeed, this species exhibits one of the most elaborate forms of pre-natal care found in the amphibian world. How does it work?
Males call for females’ attention from pre-selected leaves overhanging ponds or streams. Once the amplexus (mating) occurs, the females leave the clutches of eggs on the leaf, where they will develop into tadpoles and eventually hatch and drop into the water below. Before that happens, however, the male will stay around to actively guard his brood against parasitic flies and to keep the eggs from drying out by releasing moisture from its bladder on them.
During the day, the male will position himself strategically near the eggs, flat against the leaf, and its reticulated pattern will resemble another egg clutch, acting like a decoy for parasites and predators. Males have been observed guarding up to seven egg clutches in different stages of development at the same time (Leenders, T.), and studies demonstrate that the male’s round-the-clock attention increases the survival rate of eggs.
The Reticulated Glass Frog's easy temperament and relatively slow movements makes them a favorite to photograph. But be warned, once the frog jumps away, it will be very hard to find again. Because it is so small, it is not the best subject for wide angle macro, but its colors and shape turn it into the perfect standard macro shot. I have used both the Canon 50 mm and 100 mm macro lenses, but tend to favor the 100 mm macro, as it allows me to keep more working distance without disturbing the frog. My friend Greg (some of whose photos are featured here) loves the Sigma 150 mm macro lens for photographing glass frogs.
Whenever I go out in the forest, I always keep an eye on overhanging leaves near streams and listen for the “sheep” call of the males at night, in the hopes that I might catch another glimpse of my favorite Costa Rican frog.