10 Incredible Glass Frog Facts

These unusual amphibians are full of surprises.

Close up of glass frog at night, Costa Rica
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Glass frogs are named for their translucent skin, which helps display their internal organs from underneath (you can even watch their hearts beat). Although there are more than 150 different glass frog species worldwide, scientists have only recently come to understand many of their characteristics and quirks. And due to their tiny size and elusive nature, experts assume there are even more species hiding away, waiting to be discovered.

Here are 10 glass frog facts to help you get familiar with one of nature's most unique amphibians.

Fast Facts

  • Common Name: Glass frog
  • Scientific Name: Centrolenidae
  • Average Lifetime in the Wild: Up to 14 years
  • IUCN Red List Status: Least Concern to Critically Endangered, depending on species. 
  • Current Population: Unknown

1. Glass Frogs Are Found Only in South and Central America

Glass frog species live only in the humid montane rainforests and tropical lowland to mid-elevation mountain forests of South and Central America, including Mexico, Belize, Costa Rica, Panama, Colombia, Guatemala, and Honduras.

2. They Spend Most of Their Time in Trees

An emerald glass frog at night on a leaf.

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Glass frogs are arboreal, meaning they live primarily in trees and only come down to the ground during mating season. They are most often found near streams and rivers.

3. Glass Frogs Can Jump Long Distances

When faced with predators, glass frogs will use their climbing skills to move further into the safety of dense trees to avoid danger. If that doesn't do the trick, glass frogs will jump more than 10 feet in a single bound.

4. Only Their Undersides Are Translucent

Glass frog sitting on glass

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Glass frogs are one of the best examples of animal transparency in nature. The skin on their backs is typically a bright lime green, while their bones, intestines, heart, and other organs are visible through their underbelly. In fact, most glass frog species look much like any other type of tree frog when observed from above.

5. They're Nocturnal 

Most species of glass frogs are nocturnal, staying hidden or sleeping under tree leaves and branches during the day near streams and becoming more active at night. Once the sun goes down, glass frogs venture out into the forest to mate and hunt for food.

6. Glass Frogs Are Great at Camouflage

Silhouette of glass frog (Centronella sp.) on leaf

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The evolution of their namesake glass-like skin wasn't widely studied until 2020. Scientists found evidence that the frogs' translucency helps them blend in with their surroundings and avoid being spotted by predators. They are less likely to be seen (and thus more likely to survive for longer) than opaque frogs.

7. They Lay Their Eggs on the Undersides of Leaves

Rather than laying eggs in the water like most types of frogs, glass frogs lay their eggs on the underside of leaves overhanging a stream. After the eggs hatch, the tadpoles fall from the leaf into the water below, where they develop into frogs.

8. Male Glass Frogs Guard Their Eggs Against Predators

Reticulated glass frog with eggs in Selva Verde, Costa Rica

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Male glass frogs are very territorial and choose to stand guard over their eggs around the clock until they become tadpoles. They often find themselves fighting predators like carnivorous wasps to ensure their eggs reach the next stage of maturity unharmed.

Parental care is rare in other frogs, as only about 10% to 20% of extant species care for young after they're born.  

9. Glass Frogs Are Carnivores

Given their lack of teeth and short tongues, you may be surprised to know that glass frogs are indeed carnivores. Their diet consists mainly of small insects like ants, tiny spiders, flies, and crickets. They will even prey on other smaller frogs when the opportunity arises.

10. They Are Mainly Threatened by Deforestation

Glass frogs have plenty of predators, from giant wasps to snakes, but the most significant risk to their existence is the loss of habitat from deforestation. The Central and South American regions where glass frogs live are continuing to decrease as rainforests are cut down to make room for human and agricultural development. In 2021, for example, Mexico lost 186,000 hectares of natural forest.

Frequently Asked Questions
  • How big are glass frogs?

    Glass frogs are generally very small, weighing anywhere from 0.2 to 0.5 ounces. The Hyalinobatrachium fleischmanni, also known as the Fleischmanni's glass frog or northern glass frog, typically doesn't grow much longer than 25 millimeters.

  • Are glass frogs rare?

    Some species of glass frog are incredibly rare, such as the endangered Bolivian Cochran frog, which has gone more than a decade without being seen since the year 2000. Because of their small size and arboreal nature, glass frogs are also difficult to spot in the wild.

  • What sound do glass frogs make?

    Glass frogs make a high-pitched whistling or chirping sound to ward off predators and attract mates.

View Article Sources
  1. Barnett, James, et al. "Imperfect transparency and camouflage in glass frogs." Proceedings of the National Academy of Sciences, vol. 117, 2020, pp. 12885-12890., doi:10.1073/pnas.1919417117

  2. Delia, J., et al. "Patterns of parental care in neotropical glassfrogs." Journal of Evolutionary Biology, vol. 30, 2017, pp. 898-914., doi:10.1111/jeb.13059

  3. "Mexico Deforestation Rates & Statistics." Global Forest Watch.

  4. "Fleischmann's Glass Frog." Encyclopedia of Life.