Glass Frogs

There are over 130 species of Glass Frogs that have a translucent glass-like body. Glass Frogs can be found in the tropical forests of Central and South America, adults are generally around 3 in and 6 grams, and can live up to 15 years in captivity.

Glass Frogs are documentary favorites. Although they are called Glass Frogs, most frogs in this species usually have lemon-green or yellow skin with a translucent belly or underside. You can spot them with black, blue, green, or white spots. However, a few of them are completely translucent.

Because they are transparent, you can practically see all their organs functioning in real-time. If you look at a Glass Frog close up, you can see blood flowing through their veins and arteries. 

All species of Glass Frogs are arboreal. They can survive in elevations up to 4790 feet above sea level and typically have small bodies with pad-like toes that stick onto surfaces like trees and leaves.

Their bodies are adapted to climbing trees and sticking on to leaves even when they are wet and slippery. Glass Frogs typically have relatively long limbs with digits shaped like pads.

Furthermore, Glass Frogs are nocturnal animals so they are much harder to spot during the day.

Tips on How to Spot Glass Frogs

Glass Frogs are native to the tropical rainforests of Central and South America and the Caribbean. But they’re especially fond of the Amazon. They love the humidity and foliage there.

It is unlikely that you’ll see this variety of frogs unless you are located or visiting one of these regions. But, because of the dangerous nature of tropical forests at night, it would be best to do your exploration with extra caution. Go out with a guide if you are not a local and follow the rules in the region to remain safe.

Here are ways to spot them in the wild:

• Get a flashlight and find large trees with foliage
• Flash your light on the leaves and search for small wet bumps
• See if you can find any frog eggs or Glass Frogs themselves
• At night during mating season, they chirp gently. Follow the sound of the nearest chirping while focusing your light on the foliage.
• It’s harder to find them outside of mating season as they may be very quiet.
• If you happen to spot one, it may freeze in and try to blend with the leaf by camouflaging.
• Go close to it, but not so close that it becomes uncomfortable and leaps away. 
• Also, take heed of reptiles and other predators that hunt Glass Frogs at night.

Interesting Facts about Glass Frogs

• Most Glass Frogs’ undersides are so transparent that you can see their organs and blood pumping
• The bones of Glass Frogs are usually either white or green
• Glass frogs are carnivores and will feed on most insects and spiders
• Glass Frogs lay their eggs on leaves that are just above a water body so they can fall into the water once they become tadpoles
• Some Glass Frogs protect their eggs from predators day and night, and some even die in the process.
• Glass frogs can live up to 14 years in captivity.

More About Glass Frogs

Glass frogs are very interesting species of frogs whose transparent nature is a wonder to all who see them. For this characteristic, no Amazonian wildlife documentary is complete without their mention.

Learn more about these incredible frogs on our blog:

• 14 Fascinating Yet Bizarre Types of Frogs
• What Do Tree Frogs Eat?
• 15 Types of Tree Frogs
• 8 Tips to Find Tree Frogs
• 14 Frogs Can You Find in The Rainforest

Common Questions About Glass Frogs

How often do Glass Frogs reproduce? Glass Frogs only reproduce at the end of the rainy season once per year. Therefore, their mating season is usually between January and March. Each female lays between 14 to 30 eggs on the underside of a leaf a few meters above the water.

How big is a glass frog? Most Glass Frogs are very small and can be hard to spot in the wild since they range from 0.5 in, to 3 in long (1 cm to 7 cm). They also weigh very little at about .2 oz (6 grams).

What does a glass frog sound like? Male Glass Frogs make a certain kind of sound common to arboreal frogs of the tropics which generally sounds like the chirp of a cricket. But this is its mating call, and you will rarely hear it outside of the mating season.

What do Glass Frogs eat? Glass frogs are carnivores or meat-eaters. However, their digestive system is relatively delicate so they generally eat soft insects that they can find including earthworms, young grasshoppers, and small spiders.

What are Glass Frogs’ predators? Because of their small nature, glass frogs have several predators, including snakes, birds, monkeys, and even wasps. Not only do they like feeding upon Glass Frogs, but they also find their eggs a delicacy.

Frog flies are particularly fond of glass frog eggs. A frog fly will go to a grass frog’s nest on a leaf and lay eggs among the glass frog’s eggs. When the maggots emerge, they will eat the eggs from the inside out.

Why are Glass Frogs transparent? Glass frogs developed translucent skin to protect themselves against predators. When threatened, a glass frog will stay motionless and will deepen the color of its upper body. Its glass-like legs help it blend more with the leaf it is settled on to practically become invisible.

Are Glass Frogs endangered? Most of the 134 species of Glass Frogs have been listed as the least concerned in their conservation status. However, 60 species of these frogs are at high risk of extinction. Moreover, six among the 60 species — the Centrolene ballux, Centrolene gemmatum, Centrolene heloderma, Centrolene puyoense, Cochranella anomala, and Hyalinobatrachium crybetes — are critically endangered.

Sources

IUCN Red List, Glass Frog

Juan M. Guayasamin, Santiago Castroviejo-Fisher, José Ayarzagüena, Linda Trueb, Carles Vilà,

Phylogenetic relationships of glassfrogs (Centrolenidae) based on mitochondrial and nuclear genes, Molecular Phylogenetics and Evolution, Volume 48, Issue 2, 2008, Pages 574-595, ISSN 1055-7903, https://doi.org/10.1016/j.ympev.2008.04.012.

Imperfect transparency and camouflage in glass frogs

James B. Barnett, Constantine Michalis, Hannah M. Anderson, Brendan L. McEwen, Justin Yeager, Jonathan N. Pruitt, Nicholas E. Scott-Samuel, Innes C. Cuthill. Proceedings of the National Academy of Sciences Jun 2020, 117 (23) 12885-12890; DOI: 10.1073/pnas.1919417117