Thorny Tree Frog – Gracixalus lumarius – Rowley, Le, Dau, Hoang & Cao, 2014

Science name: Gracixalus lumarius – Rowley, Le, Dau, Hoang & Cao, 2014

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

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

Description:

Gracixalus lumarius is a medium-sized rhacophorid frog with a robust body.

Size:
Males: Snout-vent length (SVL) ranges from 38.9 to 41.6 mm.
Females: SVL is 36.3 mm in the only available adult female specimen.
Head: The head is wider than long, with a rounded snout when viewed from above. The canthus rostralis is rounded, and the interorbital region is convex.
Eyes: The pupils are horizontal and oval. The tympanum is small and about one-third the size of the eye, with a barely noticeable supratympanic fold.
Limbs: The forelimbs are robust, and the fingers vary visibly in length (I < II < IV < III) with wide disks at the tips. The hind limbs are smooth, with prominent webbing between the toes. Skin and Tubercles: The dorsal surface of adult males is covered with dense, white conical tubercles, especially during the breeding season. Females and juveniles lack these tubercles and instead have raised smooth tubercles. Coloration: Gracixalus lumarius exhibits diurnal and nocturnal color changes, with the dorsum being brown during the day and turning yellow at night. The ventral side is pink, and the flanks are bright yellow. The irises are dark gold with black reticulations.

Distribution and habitat:

Elevation:
Gracixalus lumarius, commonly known as the Thorny Tree Frog, is found at elevations between 1,845 and 2,160 meters above sea level.

Area:
This species is endemic to Vietnam, specifically within the Ngoc Linh Nature Reserve in Dak Glei District, Kon Tum Province. Its known range is highly restricted, covering an extent of 426 km², with the entire population residing in a single threat-defined location. It is possible that the species may occur in adjacent Quang Nam Province, but this has not yet been confirmed.

Habitat:
Gracixalus lumarius inhabits undisturbed montane evergreen and bamboo forests. The species is arboreal and strongly associated with relatively pristine habitats. In parts of its range that are less well-protected, habitat disturbances may be present. The species is a phytotelm breeder, meaning it lays eggs in water-filled tree holes, and the larvae likely develop as free-swimming tadpoles, although this has not been fully documented.

Behaviour and ecology:

Lifestyle:
This species is arboreal and exhibits sexual dimorphism, with males displaying conical tubercles on the dorsum, which are likely used to attract mates during the breeding season. It is a phytotelm breeder, laying its eggs on the walls of water-filled tree holes. The tadpoles probably hatch as free-swimming larvae, although this has not been directly observed.

Conservation and status:

IUCN Red List Category and Criteria:
Gracixalus lumarius is listed as Endangered on the IUCN Red List under criteria B1ab(iii), mainly due to its restricted range and the ongoing decline in habitat quality.

Population Trend:
The population trend is decreasing, with the species vulnerable to habitat degradation and loss.

Threats:

Habitat Loss: Deforestation and degradation of montane evergreen forests for agricultural activities are significant threats to the species’ habitat.
Climate Change: Changes in temperature and humidity at high elevations could also affect the habitat quality for Gracixalus lumarius.
Conservation Actions:

Protected Areas: The species is known to occur in the Ngoc Linh Nature Reserve, which offers some level of protection.
Further Research: Additional studies are needed to understand its population size, distribution, and reproductive biology to develop effective conservation strategies.