Amphibians
Flying Frog
Rhacophoridae · also called gliding frog, moss frog, Old World tree frog
Some frogs, when they run out of branch, do not fall — they glide. Wallace’s flying frog spreads four huge webbed feet, flattens its body, and sails 15 metres or more between trees to a controlled landing. It belongs to the Old World’s tree-frog family, which also holds the frogs that whip their eggs into meringue and the ones that hide as moss.
Overview
Flying frogs belong to the family Rhacophoridae, around 430 species, across sub-Saharan Africa, Madagascar, India, and Southeast Asia. This is the Old World’s tree-frog family, filling the niche that Hylidae occupies in the Americas, and it is not closely related to it. All have sticky toe pads; most are night-hunting insectivores of the canopy and understorey.
Gliding
The true gliders — Wallace’s flying frog, the Malabar and Javan gliding frogs — have hugely enlarged hands and feet with full webbing to the toe tips and skin flaps on the limbs. Spread in a leap, the whole body becomes a parachute and airfoil, and the frog glides at a shallow angle and steers to land upright, sticking with its toe pads.
Foam and moss
Many rhacophorids whip their eggs into a stiff foam nest over water, so the tadpoles develop inside the crust-protected foam before dropping into the pool. The mossy frogs have skin so patterned with green and rust tubercles that a still frog disappears against lichen, and it rolls into a ball if disturbed.
Status
Flying frogs as a family are Not Evaluated, trend decreasing. Some are common in gardens, but a large share are narrow-range specialists of single hills or streams in the Western Ghats, Sri Lanka, Borneo, and the Vietnamese mountains, and many are Endangered or Critically Endangered from deforestation, the chytrid fungus, and pet-trade collection.
Flying Frog: common questions
Can a flying frog actually fly?
No frog flies under power, but the gliding species genuinely control a descent through the air rather than just falling. When a flying frog leaps from a branch, it spreads its four feet wide, and the huge webs between the toes, together with skin flaps along the arms and legs and a flattened body, turn the animal into a set of small parachutes and wings. This slows the fall and, more importantly, converts some of the drop into forward travel and lets the frog bank and steer. A well-developed glider such as Wallace's flying frog can cover 15 metres or more from a modest height and land upright on a trunk or leaf, using its sticky toe pads to stick the landing.
What is the difference between a flying frog and an ordinary tree frog?
Flying frogs are tree frogs, specifically members of the Old World tree frog family Rhacophoridae, and only a minority of that family are true gliders. The gliding species differ from ordinary tree frogs, including their own non-gliding relatives, in having much larger hands and feet with full webbing right to the toe tips, extra skin flaps on the limbs and heels, and often a lighter build, all of which increase the surface area presented to the air. Non-gliding tree frogs have webbing that is reduced or partial, since full webs are useful for gliding and swimming but a hindrance for climbing and walking on leaves.
What is a foam nest?
A foam nest is a frothy mass of mucus, eggs, and air that a pair of frogs whips up with their hind legs during mating, usually while clinging to a branch or leaf overhanging water, or in a burrow. The outside of the foam dries into a firm crust that shields the moist interior from the sun and from many predators, while the eggs and then the tadpoles develop safely inside. When the tadpoles are ready they wriggle free and drop, or are washed by rain, into the pool below to finish growing. Foam nesting has evolved several times in frogs, and it is a hallmark of many rhacophorids and of the unrelated African and South American foam-nest frogs.
Why are so many flying frogs threatened?
The family is concentrated in exactly the places where tropical forest is being lost fastest and where biodiversity is highly localised. Many rhacophorids are found only in the moist forests of the Western Ghats of India, the wet zone of Sri Lanka, the mountains of Vietnam and southern China, or single islands and hill ranges in Southeast Asia, and a species may live in one valley and nowhere else. Clearing forest for timber, tea, oil palm, and farmland removes that habitat outright, and even fragmentation and drying of the remaining patches can be fatal for frogs tied to particular streams or humidity levels. The chytrid fungus and, for the most colourful species, collection for the international pet trade add further pressure.