Overview
The Borneo Eared Frog (Polypedates otilophus), also known as the file-eared tree frog, is one of the most visually extraordinary and charismatic anurans of Southeast Asia’s Sundaland biodiversity hotspot. Famous for the serrated, bony ridges that flare prominently above each tympanum like jagged horns or ears, this large, golden-yellow arboreal frog commands attention across the humid lowland rainforest canopies of Borneo.
Biology and Physical Characteristics
Polypedates otilophus is a substantial tree frog featuring a striking bright golden-yellow to pale cinnamon-orange dorsal coloration adorned with dozens of fine, dark brown pinstripes running longitudinally down its back. Its defining morphological feature is a prominent bony crest with sharp, saw-toothed serrations running above and behind the prominent ear drum (tympanum). The posterior surfaces of its muscular thighs are boldly marked with vibrant black-and-yellow horizontal tiger stripes, functioning as flash coloration to startle nocturnal predators.
Behavior and Ecology
Arboreal and nocturnal, the Borneo eared frog roosts high within canopy foliage during hot daylight hours, descending to low branches and shrubs overhangs above temporary rainwater pools at night. During breeding events, the female whips a protective, aerated foam nest attached to leaves suspended several feet above standing water. The developing embryos hatch within the moist foam fortress; as torrential rains dissolve the nest, the tadpoles drop safely into the aquatic nursery below.
Conservation and Human Impact
Assessed as Least Concern by the IUCN, Polypedates otilophus possesses a relatively broad geographic distribution across Borneo and demonstrates moderate resilience to secondary forest regeneration. Nonetheless, large-scale commercial deforestation for monoculture oil palm plantations and timber harvesting continue to degrade lowland river basins. The species remains well-protected in major reserves such as Danum Valley and Gunung Mulu National Park.
Interesting Factoid
The saw-toothed ‘ears’ of this frog are not soft cartilage—they are made of dense, skull-projecting cranial bone that creates a razor-sharp helmet capable of deflecting grasping predators!
Last updated: October 2026