Limestone Small Treefrog – Liuixalus calcarius – Milto, Poyarkov, Orlov & Nguyen, 2013

Science name: Liuixalus calcarius – Milto, Poyarkov, Orlov & Nguyen, 2013

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

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

Description:

Physical Characteristics: Liuixalus calcarius is a small-sized treefrog with a compact body and an obtusely pointed snout. Males typically measure around 16.5 to 18.0 mm in snout-vent length (SVL), while females are slightly larger, ranging from 20.6 to 22.0 mm. The species has a well-defined tympanum that is visible and smaller than the eye diameter. Its dorsal skin is slightly verrucosed (bumpy), and its limbs are long and slender. The coloration in life is characterized by a henna-reddish background with an X-shaped dark pattern on the back, which extends from behind the eyes to the sacrum. In females, large dark blotches are present on the sides.

Coloration: The dorsal coloration is brown with reddish markings, including an X-shaped pattern on the shoulders. There is a dark band in the interorbital region, and the limbs show transverse dark bands. The ventral surface is light in color.

Distribution and habitat:

Altitude: Liuixalus calcarius is found at low elevations, ranging from 15 to 45 meters above sea level.

Range: This species is currently known from Cat Ba Island within Cat Ba National Park, located in Hai Phong City and the Ha Long Bay area of Quang Ninh Province in northern Vietnam. The species’ estimated extent of occurrence (EOO) is 1,207 km², comprising 1–5 threat-defined locations. It is likely that the species’ range extends beyond these known localities, as similar habitats exist in adjacent areas, but further surveys are needed to confirm this.

Habitat: L. calcarius is associated with small water-filled depressions, temporary lakes, and small pools found within undisturbed and disturbed limestone karst forests. It has been observed on limestone rocks, in rock crevices, near caves, and along walking tracks close to small stream pools. These environments, particularly the limestone karst formations, are critical for the species’ survival.

Behaviour and ecology:

Lifestyle: L. calcarius is a nocturnal species and is most active at night. During the daytime, individuals hide in rock crevices and caves. The frogs are dependent on the limestone karst landscape for shelter and breeding.

Reproduction: Little is known about the species’ reproductive biology, though calling males have been observed in April, indicating that this may be the breeding season. It is presumed that, like other rhacophorid frogs, L. calcarius breeds in water, with larval development occurring in small pools or water-filled depressions.

Feeding: Specific dietary details are not available for L. calcarius, but it is likely insectivorous, feeding on small invertebrates commonly found in its karst forest habitat.

Conservation and status:

IUCN Red List Category and Criteria: Liuixalus calcarius is listed as Endangered under the IUCN Red List criteria B1ab(iii), which indicates that the species is at risk due to a declining habitat. The assessment was last conducted in September 2020.

Threats: The primary threat to L. calcarius is the ongoing decline in the extent and quality of its forest habitat. This degradation is driven mainly by agricultural activities and, to a lesser extent, local subsistence use of forest resources. Habitat destruction, particularly the clearing of forested areas for agriculture, poses a significant threat to the species’ survival.

Conservation Actions: Currently, there are no specific conservation measures in place for L. calcarius. However, the species is found within Cat Ba National Park, which provides some level of protection. Conservation efforts should focus on habitat preservation and restoration, particularly in the limestone karst areas, to prevent further habitat loss. Additionally, further research is needed to better understand the species’ population size, distribution, and ecology.