Vietnamese Mossy Frog

Vietnamese mossy frog（圖片來源：Caitlin 0000，採用 CC BY 4.0 授權）

The Vietnamese mossy frog (Theloderma corticale), also known as the Tonkin bug-eyed frog, is a semi-aquatic tree frog belonging to the family Rhacophoridae. It is distributed across northern Vietnam, central to southern Laos, and southern China (including Guangdong, Guangxi, Hainan, and Yunnan). Its natural habitats include tropical and subtropical evergreen broadleaf forests, montane rainforests, rocky caves, stream margins, and water-filled tree hollows. It typically occurs at elevations ranging from approximately 470 to 1500 meters, where conditions are relatively cool and humid.

This species is best known for its green and brown mottled skin covered in irregular wart-like projections, giving it the appearance of moss-covered rocks or bark. This remarkable camouflage allows it to blend seamlessly into its surroundings. When threatened, individuals may curl into a ball and remain motionless, feigning death to avoid predators. Adult females are larger, reaching 8 to 9 cm in length, while males are usually 6 to 7 cm.

Vietnamese mossy frogs are nocturnal. During the day, they remain hidden in crevices, tree hollows, or rock gaps, becoming active at night to forage. Their diet consists mainly of insects and other small invertebrates, including crickets, cockroaches, and worms. Although their habitats are increasingly affected by deforestation and collection for the pet trade, they are currently listed as Least Concern by the International Union for Conservation of Nature (IUCN). In captivity, their unique appearance and tolerance to cooler temperatures have made them popular, though their sensitivity means they are not ideal for complete beginners.

Housing Requirements in Captivity

As a semi-aquatic species, Vietnamese mossy frogs require an enclosure that includes both aquatic and terrestrial areas. A paludarium-style setup is recommended, with a minimum size of 45×45×60 cm for 2 to 4 individuals. Larger enclosures are preferable for housing more frogs or for creating a more naturalistic environment.

The aquatic section should have a water depth of 2 to 4 cm, using dechlorinated water. Adding dried leaves such as oak leaves helps release tannins, creating conditions similar to their natural habitat. The water should not be overly clear; a slightly tea-colored appearance is more suitable. A filtration system can help reduce waste accumulation, but partial water changes should still be performed every two weeks.

The terrestrial area can be structured with cork bark, driftwood, and rocks to provide climbing surfaces and hiding spaces. Because of their strong camouflage behavior, incorporating live moss and humidity-tolerant plants such as pothos or peace lilies helps maintain moisture and offers natural shelter.

These frogs prefer cool, humid environments. Daytime temperatures should be maintained between 18 and 24°C, with nighttime temperatures dropping to 15 to 20°C. Temperatures above 26°C must be avoided, as excessive heat can cause severe stress or death. Humidity should be kept between 80 and 100 percent, maintained through regular misting or automated systems. Lighting is not essential due to their nocturnal habits, but low-level UVB or plant lighting can be used if live plants are present.

The enclosure should be cleaned regularly by removing uneaten food and waste. Partial cleaning should be done weekly, with partial water replacement monthly to maintain a stable microenvironment. Their skin is highly sensitive to chemicals, so untreated tap water and cleaning agents must never be used.

Vietnamese mossy frog（圖片來源：Katie Chan，採用 CC BY-SA 4.0 授權）

Feeding Conditions

Vietnamese mossy frogs primarily feed on insects and other small invertebrates. In the wild, they consume prey such as crickets, cockroaches, and worms. In captivity, suitable food items include crickets, Dubia roaches, fruit flies, and occasional earthworms.

Live prey should always be provided, as these frogs respond strongly to movement. Feeding is recommended 2 to 3 times per week, offering 2 to 6 crickets per feeding depending on the size and age of the frog. Juveniles can be fed small crickets daily, ensuring the prey size is smaller than the width of the frog's head. Adults can consume medium to large crickets. Due to their relatively slow metabolism, daily feeding is unnecessary and may lead to obesity.

Feeder insects should be gut-loaded beforehand with nutritious foods such as carrots or oats to enhance their nutritional value. Additionally, insects should be dusted with calcium powder and vitamin D3 once or twice per week before feeding, helping prevent nutritional deficiencies and metabolic bone disease.

Because enclosures often include a water section, crickets may fall into the water and drown. To prevent waste and water contamination, small feeding dishes or floating feeding platforms should be used on the terrestrial side. Feeding is best done in the evening before lights are turned off, when the frogs are most active.

Breeding Conditions

In the wild, breeding typically occurs during the rainy season, when males call to attract females. Eggs are laid in crevices near water, such as gaps in bark or rock surfaces, usually positioned just above the waterline. After several days, the hatched tadpoles drop into the water, where they undergo aquatic development. Metamorphosis into froglets takes approximately 4 to 6 months.

In captivity, breeding is moderately challenging and requires high humidity, lower temperatures, and simulation of rainy season conditions through frequent misting and slight temperature reduction. Successful breeding often involves one female paired with two to three males, increasing fertilization success.

Adult females are larger, while males possess reddish or pink nuptial pads on their forelimbs. Juveniles are difficult to sex, making selection of breeding individuals challenging.

Tadpoles should be kept in shallow water at temperatures around 18 to 20°C. Dried leaves can be added to provide tannins and shelter. They can be fed algae wafers, crushed crickets, or spirulina powder. As they develop limbs and begin transitioning to land, an accessible area must be provided for them to emerge. Newly metamorphosed froglets should be fed small fruit flies or small crickets, and enclosures should be checked daily for uneaten food.

For most keepers, breeding Vietnamese mossy frogs is not necessary. If tadpoles are produced unexpectedly, additional containers should be prepared, and consideration should be given to transferring them responsibly to experienced keepers or breeders.

Preventing Invasive Spread

The Vietnamese mossy frog is native to Southeast Asia and is not indigenous to Taiwan. Although there are no confirmed records of it becoming invasive in Taiwan or other non-native regions, keepers must never release captive individuals into the wild. If introduced, they may compete with native amphibians for resources or spread pathogens such as chytrid fungus, causing irreversible ecological damage.

Owners should be prepared for long-term care. If they are unable to continue keeping these animals, they should rehome them responsibly through legal channels or transfer them to appropriate animal care facilities. Under no circumstances should Vietnamese mossy frogs be released into natural environments.

Author: Shui-Ye You