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The mossy frog, Theloderma corticale, is a semi-aquatic member of the family Rhacophoridae named for a knobbly, mottled skin that mimics moss growing over bark or rock. It is native to northern Vietnam, south-central Laos, and southern China’s Guangdong, Guangxi, Hainan and Yunnan provinces, where it lives among the caves, cliffs and forest streams of the region rather than out in the open canopy favoured by many other tree frogs. Despite heavy demand from the international pet trade, it remains widespread enough to be classed as of Least Concern.
Within its genus, Theloderma, the species is one of the better-known members thanks to its distinctive look and its long history in the terrarium hobby, where keepers prize it for the same bark-like texture that hides it from predators in the wild. That popularity has made it one of the more thoroughly documented Southeast Asian frogs in captivity, even though field studies of its wild population remain comparatively sparse.
Identification
The frog’s rough, bumpy skin is mottled green and brown, a pattern that, combined with warty tubercles across the back, makes an individual sitting still on wet rock or bark almost impossible to pick out — the resemblance to a patch of moss is what gives the species its common name. It carries large, sticky toe pads and a soft underbelly, the pads an adaptation for gripping the wet rock and tree surfaces it climbs. There is a marked size difference between the sexes: males reach about 61 mm in snout-vent length, while females grow substantially larger, from 80 to 90 mm, a gap wide enough that the two sexes are easy to tell apart on size alone once a specimen is in hand. When a predator gets too close, the mossy frog does not flee; instead it curls into a tight ball and feigns death (thanatosis), trusting its camouflage to complete the disguise rather than relying on speed or a toxic secretion the way many other rainforest frogs do.
Habitat and range
Theloderma corticale occupies evergreen rainforest and subtropical forest across northern Vietnam, south-central Laos and four southern Chinese provinces, typically between 470 and 1,500 m elevation. Rather than living in open water, it is semi-aquatic in a narrower sense: it shelters in caves and on steep, wet rocky cliffs, venturing to standing water only for breeding. Suitable habitat is patchy, since it depends on the combination of rock faces, hollowed logs or tree cavities, and nearby water that karst forest terrain provides.
Behaviour and breeding
Mossy frogs breed in rock cavities or tree hollows positioned above a body of water, an unusual choice that means the eggs never touch the water directly. Once the tadpoles hatch, they drop down into the pool beneath, where they complete their development feeding on small aquatic invertebrates. As adults, they hunt on land, taking crickets, cockroaches and earthworms among the invertebrates available around their rocky shelters. In captivity, where the species is popular for its striking looks, individuals have been recorded living for up to 20 years, although breeding it successfully away from its native caves and cliffs remains difficult.
Conservation
Theloderma corticale is classed as Least Concern, as shown in the facts box above. Its range across four Chinese provinces plus northern Vietnam and Laos gives it enough breadth to withstand local habitat loss, but the picture is not without pressure: forest clearance, over-collection for the international pet trade, and susceptibility to the amphibian chytrid fungus (Batrachochytrium dendrobatidis) are all recognised threats. Its popularity in the terrarium hobby, driven by the same moss-like appearance that protects it in the wild, is a direct source of continued collection pressure, even as captive breeding programs slowly reduce reliance on wild-caught animals.
Similar species
Within the genus Theloderma, several relatives share the warty, camouflaged look, but T. corticale stands out for its size (females reaching 80–90 mm are large for the genus) and for its green-and-brown mottling paired with a soft, pale underbelly. Its cave- and cliff-dwelling habit, rather than the more arboreal lifestyle of many rhacophorid tree frogs, together with its Vietnam-to-southern-China range, sets it apart from unrelated moss- or bark-mimicking frogs from other regions.