Nguyen’s Wart Frog – Limnonectes nguyenorum – McLeod, Kurlbaum & Hoang, 2015

Science name: Limnonectes nguyenorum – McLeod, Kurlbaum & Hoang, 2015

Taxonomic:  Animalia>> Chordata>> Amphibia>> Anura >> Dicroglossidae >> nguyenorum

Species status: Endemic ; IUCN status: NT (Near Threatened)

Description: Physical Characteristics: Limnonectes nguyenorum is a small species of frog within the family Dicroglossidae. Adult males have a snout-vent length (SVL) ranging from 43.5 to 43.8 mm, while females measure between 36.5 and 43.6 mm. The species exhibits sexual dimorphism, with males displaying nuptial pads on their first and second fingers. Both males and females have elongated heads, longer than they are wide, and possess robust odontoid processes, or fangs, on their lower jaws—a characteristic feature of fanged frogs.

Coloration and Appearance: The species is light brown on its dorsal side, with dark brown markings and an inverted chevron pattern on the shoulders. The ventral surface is typically immaculate, although some mottling may be observed on the throat and hind limbs. Distinctive white spots are present along the upper lip, and a dark brown bar runs from the tip of the snout through the eye to the arm. The skin on the dorsal surface is feebly crenulate, while the ventral side is smooth.

Distribution and habitat: Altitude: Limnonectes nguyenorum is found at elevations between 240 to 1,300 meters above sea level. Its habitats are typically located in the montane and lowland areas of northern Vietnam.

Range: This species is known from the northern Vietnamese provinces of Ha Giang, Lao Cai, Son La, and Vinh Phuc. Its range extends across a small number of locations, with an estimated extent of occurrence (EOO) of approximately 28,307 km². Although it has not been confirmed, Limnonectes nguyenorum may also occur in nearby regions, such as Yunnan Province in China, where suitable habitat exists. The species’ potential range includes adjacent areas with similar environmental conditions, though further surveys are required to confirm its presence in these regions.

Habitat: Limnonectes nguyenorum is associated with small, shallow, rocky streams in primary and secondary evergreen forests. These habitats provide essential moisture and cover, particularly in montane and lowland tropical forests. The species has been found in disturbed areas near streams, including those affected by shifting cultivation and agriculture. It appears to require intact forest cover and may be sensitive to habitat loss, as ongoing declines in forest extent and quality have been observed.

Behaviour and ecology: Lifestyle: Limnonectes nguyenorum is a terrestrial, non-migratory species associated with freshwater streams in forested areas. It relies on intact evergreen forests, where it can be found near rocky, shallow streams. This species has been recorded in both primary and secondary forests and may be present in habitats affected by human activities, such as agriculture, though its tolerance for anthropogenic disturbance is uncertain.

Feeding: Like other species in the genus Limnonectes, L. nguyenorum likely feeds on small invertebrates, such as insects and other arthropods, found near its streamside habitats.

Reproduction: Reproductive activity has been observed in gravid females from May to June, with egg clutches deposited on submerged rocks or overhanging vegetation above streams. Larval development occurs in these streams, where tadpoles feed and grow before undergoing metamorphosis. The species’ breeding season coincides with the early wet season, when conditions are optimal for egg deposition and larval development.

Conservation and status: IUCN Red List Category and Criteria: Limnonectes nguyenorum is listed as Near Threatened under the IUCN Red List criteria B1ab(iii,v), last assessed in 2020. The species faces significant threats from habitat loss, primarily due to deforestation and shifting cultivation, which contribute to the ongoing decline in its population.

Threats: The most significant threat to L. nguyenorum is the degradation of its forest habitat. Agricultural expansion, including shifting cultivation, and infrastructure development have led to a reduction in the extent and quality of the forests where this species resides. Additionally, habitat fragmentation and loss of wetland areas, such as streams and rivers, further threaten the species.

Conservation Actions: While there are no specific conservation measures targeting L. nguyenorum, the species benefits from being located within some protected areas in northern Vietnam. Future conservation efforts should focus on the preservation of montane and lowland evergreen forests, particularly around stream habitats critical for reproduction. Surveys are also needed to better understand the species’ population trends, habitat requirements, and tolerance to habitat disturbance. Improved forest management and protection of riparian zones would help mitigate the threats posed by deforestation and agriculture.