Schlegel's Green Tree Frog

Fascinating facts about the Schlegel's Green Tree Frog

• When spring thaws, these frogs tunnel from rice paddies into holes just above the water, digging a cavity 6–9 cm wide and 10–15 cm high.
• The female carries the much smaller male into the nest, and together they create a 6–7 cm thick foam ball full of air bubbles that cushions the eggs. This foam turns liquid after a few days, spilling the hatchlings into the water below, a strategy that blends parental care with the environment’s own resources.
• Males grow to 32–43 mm while females reach 43–53 mm from snout to vent. They have truncated fingertip discs with circummarginal grooves.
• Endemic to Japan, the species occupies hilly forests to lowland paddy fields across Honshu, Shikoku, Kyushu, and the Ryukyu Islands.
• The International Union for Conservation of Nature lists the frog as not threatened.

At a glance

About the Schlegel's Green Tree Frog

Schlegel's green tree frog, Zhangixalus schlegelii, is a sleek amphibian native solely to Japan, inhabiting Honshu, Shikoku, Kyushu, and the Ryukyu Islands. Males range from 32 to 43 mm and females from 43 to 53 mm in snout-vent length, their bodies cloaked in almost entirely smooth dorsal skin. The frog’s fingertips end in truncated discs bordered by circummarginal grooves, while its webbing remains modest. Males are distinguished by yellow-white nuptial pads, a darkly colored throat, and a pair of slit-like vocal openings, all framed by a prominent supra-tympanic fold that lacks a dorsolateral counterpart. This subtle yet striking morphology allows the species to navigate the temperate wetlands and forested hillsides it favors, from lowland paddy fields to higher-elevation swamps, where it spends much of its life perched among reeds and low vegetation. When winter’s chill recedes, the frogs emerge to a ritual that sets them apart: they excavate shallow holes just above water level, 6–9 cm wide and 10–15 cm deep, and create underground foam nests. The female, carrying the smaller male, deposits a thick, aerated white mass that she kneads with her feet, breaking large bubbles into a fine, protective foam that envelops the eggs. After fertilization, the parents abandon the nest, leaving the foam to liquefy and release the hatchlings into the surrounding water. This underground, foam-filled nursery, a surprising adaptation among tree-frogs, ensures moisture and oxygen for the developing young before they join the bustling life of Japan’s rice paddies and wetlands.

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