Misty moss frog – Theloderma nebulosum – Rowley, Le, Hoang, Dau & Cao, 2011

Science name: Theloderma nebulosum – Rowley, Le, Hoang, Dau & Cao, 2011

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

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

Description: Physical Characteristics:
Theloderma nebulosum is a small frog, with adult females reaching a snout-vent length (SVL) of approximately 29.2 mm. The species has a brown dorsum with indistinct darker brown longitudinal markings. The skin texture on its dorsal surface is slightly rugose, with minute, sparsely distributed asperities. This species lacks webbing on its fingers, but its toes are partially webbed. The Misty Moss Frog is further distinguished by its bicolored iris, which is pale gold in the upper third and dark reddish-brown in the lower two-thirds, creating a striking visual contrast.

Its snout is blunt and rounded, and the species does not possess vomerine teeth. The fingers and toes of Theloderma nebulosum are tipped with well-developed disks, aiding in its semi-arboreal lifestyle. The distinctive smooth dorsal surface and brown coloration with minimal markings distinguish this species from its congeners.

Distribution and habitat: Altitude:
Theloderma nebulosum, commonly known as the Misty Moss Frog, inhabits high-elevation montane regions at altitudes ranging from 1,950 to 2,000 meters above sea level (asl).

Range:
This species is native to Vietnam, specifically found on Ngoc Linh Mountain within Ngoc Linh Nature Reserve, located in Dak Glei District, Kon Tum Province. The Misty Moss Frog is restricted to this isolated high-elevation area, which is known for its endemic fauna. The species’ estimated extent of occurrence (EOO) is 940 km². While it is currently confined to this single location, further surveys may reveal additional populations in adjacent areas with similar habitat characteristics.

Habitat:
The Misty Moss Frog is closely associated with montane evergreen and bamboo forests in regions that experience high rainfall and humidity. These forests are typically shrouded in mist, creating a unique and wet environment. Tadpoles have been observed developing in small water-filled tree hollows about one meter above the ground. Due to its dependence on undisturbed, high-elevation forests, any degradation of its habitat poses a significant threat to the species’ survival. The species has not been recorded in disturbed areas, emphasizing its reliance on pristine forest environments.

Behaviour and ecology: Lifestyle:
Theloderma nebulosum is a montane forest specialist and is often found in bamboo and evergreen forests. Individuals are typically observed on vegetation or in tree hollows, particularly in very wet conditions that are common in its misty habitat. The species is believed to be arboreal, relying on its well-developed toe disks to navigate the trees. Tadpoles have been found in small water-filled tree hollows, indicating that the species likely breeds in these phytotelmic environments. Weather conditions, particularly high humidity and frequent rainfall, likely play a significant role in their behavior and reproductive cycles.

Reproduction:
In the wild, Theloderma nebulosum has been observed to lay eggs in water-filled tree hollows. A clutch of eight tadpoles was found in a small tree hollow about one meter above the ground. These hollows serve as a protective environment for the developing tadpoles, which metamorphose into adult frogs over time. The species’ reproductive biology is closely tied to its wet montane habitat, although further studies are required to fully understand the details of its breeding behavior and lifecycle.

Conservation and status: IUCN Red List Category and Criteria:
Theloderma nebulosum is listed as “Endangered” on the IUCN Red List under the criteria B1ab(iii). This listing is due to its extremely limited distribution, restricted to a single location on Ngoc Linh Mountain, and the ongoing decline in the quality and extent of its montane forest habitat. The species was last assessed in 2015, and its population trend is considered to be decreasing.

Threats:
The primary threat to Theloderma nebulosum is habitat loss and degradation, particularly from agricultural expansion and deforestation in and around its montane forest habitat. The conversion of forested land for agriculture reduces the available habitat for this species, further fragmenting its already limited range. Logging and other human activities continue to degrade the forest, affecting the environmental conditions necessary for the survival of this forest-dependent species.

Conservation Actions:
Conservation efforts must focus on protecting the species’ high-elevation montane forest habitat. This includes preventing further deforestation and habitat fragmentation within Ngoc Linh Nature Reserve. Further research is needed to monitor the population of Theloderma nebulosum and to determine if it occurs in other nearby areas with similar habitat conditions. Expanding the boundaries of protected areas and increasing conservation efforts in these regions are crucial for ensuring the long-term survival of this species.