Overview
The Frilled Tree Frog (Kurixalus appendiculatus), also known as the Southeast Asian mossy frog or rough-backed tree frog, is a master of cryptic camouflage native to the tropical rainforests of Sundaland. Belonging to the tree frog family Rhacophoridae, this miniature amphibian is renowned for its jagged dermal fringes and scalloped skin flaps running along its forearms, heels, and body margins. Perfectly mimicking lichen-encrusted tree bark, it vanishes completely from the sight of predators on the wet forest trunks of Borneo and Sumatra.
Biology and Physical Characteristics
Kurixalus appendiculatus displays a flattened, compact body, large protuberant bronze eyes with horizontal pupils, and prominent expanded adhesive digital discs on its fingers and toes. Its dorsal skin is rough and tuberculate, covered in fine granules and jagged, scalloped dermal flaps extending along the outer edges of the arms and legs, as well as a pointed triangular flap on the snout. Coloration is an intricate, mottled mosaic of lichen-gray, mossy green, cream, and reddish-brown, allowing it to seamlessly match damp, moss-covered tree bark.
Behavior and Ecology
Nocturnal and arboreal, the frilled tree frog rests motionlessly during the daytime by flattening its body tightly against tree trunks, saplings, or buttress roots. Its scalloped dermal fringes break up the frog’s physical silhouette and eliminate telltale cast shadows. At night, breeding males gather in low shrubs and emergent vegetation around temporary pools, muddy animal wallows, and sluggish rainforest streams, producing quiet, insect-like clicking calls to attract females. Eggs are deposited on vegetation or muddy banks above standing water, where hatching tadpoles drop into the water to develop.
Conservation and Human Impact
Assessed as Least Concern by the IUCN, the frilled tree frog is widely distributed and locally abundant across Sundaland. While widespread commercial palm oil conversion and clear-cut logging in lowland Borneo and Sumatra have degraded vast swathes of native forest, the species shows remarkable resilience, surviving in selectively logged forests, secondary growth, and protected national parks such as Gunung Mulu and Danum Valley.
Interesting Factoid
The scalloped, frilly skin fringes along the frog’s limbs and feet act as biological shadow-eliminators: when the frog presses flat against a tree trunk, the ruffled fringes smooth the transition between body and bark, preventing casting shadows that would reveal its location to sharp-eyed birds.
Last updated: October 2026