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glass frog sticked to a window monteverde
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Glass Frogs

Glass Frogs


  • Scientific Name: Hyalinobatrachium fleischmanni
  • Status in the Wild: Common
  • Habitat: Cloud Forests, Rainforests, Rivers, Tropical Dry Forests
  • Diet: Carnivore

Nature's original X-ray machine, the Fleischmann's glass frog has a transparent underbelly that reveals a complex web of veins, organs and tiny white bones. The frog's physical uniqueness continues with its translucent yellow fingertips and captivating eyes – golden irises and elliptical pupils that are surrounded by iridescent, marbled color variations.

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The Fleischmann's glass frog is also commonly known as the northern glass frog, or "ranita de vidrio" (literally, glass frog) in Spanish. Averaging less than an inch in length, both males and females have flat bodies, broad heads, rounded snouts and pale, green skin that usually displays faint yellow spots. Their undersides are transparent, save for an opaque layer of white tissue that surrounds their digestive systems.

Northern glass frogs are arboreal and nocturnal, meaning they live in trees and are most active at night. Little is known about the frog's diet, but researchers think they feed on insects, fish and smaller frogs.


The Fleischmann's glass frog ranges from central Mexico south into northern Venezuela and Ecuador. They prefer lower elevations, and generally live in vegetated areas close to streams and rivers. Occasionally, Fleischmann's glass frogs live in deforested areas and open pastureland. In Costa Rica, they are commonly spotted in Arenal, Monteverde, Tortuguero, and in the surrounds of Tapanti National Park.


Male glass frogs are very territorial, and often engage in physical altercations during mating season (March-November). Males call to females with a distinct "wheet" sound, repeated with short pauses in between each call. When a male invades an established mating territory, the defending male warns with "wheet" and "mew" calls; if the invader does not back off, the resident male provokes an attack. After a winner is declared, the loser withdraws and the dominant male is left to reproduce with any resident females.

Fleischmann's glass frogs breed in streams. After reproduction, females lay clutches of 18-30 eggs in moist areas, usually on the underside of a leaf that overhangs water. During the incubation process, both male and female frogs care for the eggs, either by sitting on them at night or sleeping near, but not on, them throughout the day. In order to prevent desiccation – one of the most common causes of glass frog embryo mortality – male frogs water the eggs with their urine.

Status in the Wild:

Fleischmann's glass frogs are considered a species of least concern, and are prevalent throughout Costa Rica. National research has shown them to be resistant to habitat alteration and polluted water sources, but even so, populations are declining in Monteverde. Major threats to this species are usually related to human development – deforestation, logging, petrochemicals, and illegal crops – but they are also sensitive to chytridiomycosis and other fungal infections. They have many predators, especially the ctenid spider.  

Glass Frogs in Pictures

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