Vietnam Flying Frog – Rhacophorus calcaneus – Smith, 1924

Science name: Rhacophorus calcaneus – Smith, 1924

Taxonomic:  Animalia>> Chordata>> Amphibia>> Anura >> Rhacophoridae >> calcaneus

Species status: Endemic ; IUCN status: EN (Endangered Species)

Description:

Physical Characteristics:
Rhacophorus calcaneus, commonly known as the Vietnam Flying Frog, has a head that is as long as it is wide, with a slightly pointed snout. The eyes are large, and the tympanum is distinct but smaller than the eye. The species exhibits sexual dimorphism, with males typically being smaller than females. The body is brownish-red, with striking yellow stripes running from the back of the eyes to the groin, and a third stripe along the back. The frog’s limbs, including its webbed feet, are colored yellow to orange, with dark patches on the sides of the body and legs.

Distribution and habitat:

Altitude:
Rhacophorus calcaneus is found at elevations ranging from 1,300 to 2,000 meters above sea level (asl).

Range:
This species is known from five locations in the Central Highlands of Vietnam, specifically in the provinces of Lam Dong, Dak Lak, and Khanh Hoa. Its range may extend into adjacent areas, such as western Ninh Thuan Province, where similar habitats are found. The species’ estimated extent of occurrence (EOO) is 4,138 km². Further surveys in these regions may uncover additional populations.

Habitat:
Rhacophorus calcaneus inhabits evergreen forests and is primarily arboreal. It is most commonly observed on trees or other vegetation near streams, particularly around cascades. The species depends on forested wetlands, breeding in streams and laying eggs on leaves or branches overhanging water. Tadpoles develop in pools within streams, indicating its reliance on slow-moving or standing water bodies for reproduction.

Behaviour and ecology:

Lifestyle:
Rhacophorus calcaneus is an arboreal species, spending much of its life in the trees, particularly in forested areas near streams. It is observed during the early rainy season, when it breeds. Pairs of frogs engage in amplexus (mating embrace), and eggs are laid on leaves or branches. The species relies on slow-moving streams or pools for breeding, and tadpoles are carried into these water bodies by rain.

Reproduction:
Breeding occurs primarily during the early rainy season, between March and May. Males call from trees to attract females, and eggs are laid in foam nests on overhanging vegetation. The tadpoles develop in water and eventually metamorphose into adult frogs, completing their life cycle.

Conservation and status:

Distribution and Habitat

Altitude:
Rhacophorus calcaneus is found at elevations ranging from 1,300 to 2,000 meters above sea level (asl).

Range:
This species is known from five locations in the Central Highlands of Vietnam, specifically in the provinces of Lam Dong, Dak Lak, and Khanh Hoa. Its range may extend into adjacent areas, such as western Ninh Thuan Province, where similar habitats are found. The species’ estimated extent of occurrence (EOO) is 4,138 km². Further surveys in these regions may uncover additional populations.

Habitat:
Rhacophorus calcaneus inhabits evergreen forests and is primarily arboreal. It is most commonly observed on trees or other vegetation near streams, particularly around cascades. The species depends on forested wetlands, breeding in streams and laying eggs on leaves or branches overhanging water. Tadpoles develop in pools within streams, indicating its reliance on slow-moving or standing water bodies for reproduction.

Description

Physical Characteristics:
Rhacophorus calcaneus, commonly known as the Vietnam Flying Frog, has a head that is as long as it is wide, with a slightly pointed snout. The eyes are large, and the tympanum is distinct but smaller than the eye. The species exhibits sexual dimorphism, with males typically being smaller than females. The body is brownish-red, with striking yellow stripes running from the back of the eyes to the groin, and a third stripe along the back. The frog’s limbs, including its webbed feet, are colored yellow to orange, with dark patches on the sides of the body and legs.

Behavior and Ecology

Lifestyle:
Rhacophorus calcaneus is an arboreal species, spending much of its life in the trees, particularly in forested areas near streams. It is observed during the early rainy season, when it breeds. Pairs of frogs engage in amplexus (mating embrace), and eggs are laid on leaves or branches. The species relies on slow-moving streams or pools for breeding, and tadpoles are carried into these water bodies by rain.

Reproduction:
Breeding occurs primarily during the early rainy season, between March and May. Males call from trees to attract females, and eggs are laid in foam nests on overhanging vegetation. The tadpoles develop in water and eventually metamorphose into adult frogs, completing their life cycle.

Conservation and Status

IUCN Red List Category and Criteria:
Rhacophorus calcaneus is listed as “Endangered” under the IUCN Red List due to its limited range and ongoing habitat loss. It was last assessed in 2015.

Threats:
The primary threats to Rhacophorus calcaneus include habitat degradation and deforestation. The species’ montane forest habitat is increasingly impacted by logging, agriculture, and infrastructure development. Forest loss and degradation are particularly concerning in the Central Highlands, where this species is found.

Conservation Actions:
While no specific conservation measures are currently in place for Rhacophorus calcaneus, the species benefits from protection within several national parks and nature reserves, including Chu Yang Sin National Park and Bidoup-Nui Ba National Park. Further research and surveys are needed to better understand its population trends, distribution, and ecological requirements, and to develop targeted conservation strategies.