Vietnam Spadefoot Toad – Leptobrachium pullum – (Smith, 1921)

Science name: Leptobrachium pullum – (Smith, 1921)

Taxonomic:  Animalia>> Chordata>> Amphibia>> Anura >> Megophryidae >> pullum

Species status: Endemic ; IUCN status: LC (Least Concern)

Description:

Physical Characteristics: Leptobrachium pullum is a member of the Megophryidae family, a group of frogs commonly known for their cryptic appearances and adaptation to life in forested environments. Males of this species typically have a snout-vent length (SVL) ranging from 41.3 mm to 50.6 mm, while females are slightly larger, reaching up to 52.4 mm. The species has a broad and slightly depressed head, contributing to its flattened appearance. The skin on the dorsal (upper) side is generally smooth, though it may exhibit slight texturing in certain individuals.

Coloration and Appearance: One of the most distinctive features of Leptobrachium pullum is the color of its eyes. The upper one-third to one-half of the iris is typically scarlet, which gives the species a striking red-eyed appearance. This eye coloration is a key characteristic used to identify the species in the wild. The dorsal coloration of the species is generally dark brown to black, which allows it to blend in with the forest floor and the surrounding leaf litter. The ventral (underneath) side is lighter in color, often featuring dark spots. Unlike many other species in the Megophryidae family, Leptobrachium pullum does not have large, prominent dorsal markings. However, some individuals may exhibit lighter spots on the belly (venter). This relatively muted coloration is typical of species that are well-adapted to forested environments, where camouflage is crucial for avoiding predators.

Distribution and habitat:

Altitude: Leptobrachium pullum is found at altitudes ranging from 553 to 2,113 meters above sea level. This broad range in elevation allows the species to thrive in various montane habitats, where temperature and moisture levels are suitable for amphibian life.

Range: This species is native to central-southern Vietnam, specifically concentrated around the Langbian Plateau. The Langbian Plateau is characterized by a combination of high-altitude forested landscapes and rocky terrain, providing an ideal habitat for Leptobrachium pullum. Its distribution is thought to extend into neighboring regions of southern Laos and eastern Cambodia due to the presence of similar habitats in those regions. However, despite the environmental similarity, no confirmed sightings have been reported from these countries. This gap in confirmed distribution suggests that further surveys may be required to clarify the true range of the species.

Habitat: Leptobrachium pullum primarily inhabits montane evergreen forests, where dense vegetation and rocky substrates are abundant. These forests typically feature a canopy of broad-leaved trees and a thick understory, creating a moist microclimate favorable to amphibians. The species is often found near rocky streams, ponds, and areas with significant leaf litter. This leaf litter provides cover, as well as habitat for the invertebrates that likely constitute a major part of its diet. Additionally, the species has been observed in wetland habitats, including permanent rivers, streams, and creeks. These freshwater environments are crucial for the species’ reproductive cycle, as they provide the necessary conditions for aquatic larval development. Leptobrachium pullum prefers subtropical and tropical moist montane forests, which are characterized by high humidity, frequent rainfall, and moderate temperatures, typical of its montane habitat.

Behaviour and ecology:

Lifestyle: Leptobrachium pullum is a terrestrial species, meaning it spends the majority of its life on land rather than in water. Unlike some amphibians that migrate seasonally, Leptobrachium pullum is non-migratory, remaining in or near its forested habitat year-round. It is typically found in montane evergreen forests and wetlands, often in areas with dense leaf litter or on stones near streams and ponds. This species is closely associated with the humid microhabitats created by leaf litter and rocky streambeds, where it can find shelter and food.

Feeding: There is limited direct information on the specific diet of Leptobrachium pullum. However, like many amphibians, it is likely to feed on a variety of small invertebrates, including insects, spiders, and other arthropods. These prey items are commonly found in the leaf litter or near water sources, which align with the species’ habitat preferences. The species’ broad head and mouth likely facilitate the capture of these small invertebrates as it forages on the forest floor or along the edges of streams.

Reproduction: Leptobrachium pullum breeds during the wet season, with reproductive activity peaking around August. During this period, males and females have been observed in amplexus, a mating position where the male clasps the female from above. Amplexus is typical among frogs and is crucial for the external fertilization of eggs. The eggs are laid in freshwater environments such as streams or ponds, where they undergo aquatic larval development. The tadpoles of Leptobrachium pullum are fully aquatic, relying on the oxygenated water of streams or ponds to grow and develop before metamorphosing into terrestrial adults.

Conservation and status:

IUCN Red List Category and Criteria: Leptobrachium pullum is listed as Least Concern on the IUCN Red List (2017). Despite this relatively favorable status, the species’ population is considered to be in decline, primarily due to habitat degradation.

Threats: The most significant threat facing Leptobrachium pullum is habitat degradation, which is largely driven by agricultural expansion. As agriculture expands into montane regions, it results in deforestation, reducing both the quality and extent of the species’ natural habitats. Wetlands, streams, and forested areas that Leptobrachium pullum depends on for breeding and shelter are being lost or fragmented, impacting the species’ ability to thrive. Additionally, other human activities such as logging and infrastructure development may further contribute to habitat loss and degradation.

Conservation Actions: While Leptobrachium pullum is currently classified as Least Concern, the species requires ongoing habitat protection to prevent further declines. It benefits from occurring in some protected areas, but more research is needed to monitor population trends and habitat conditions. Specifically, studies on the effects of habitat degradation, population fragmentation, and potential shifts in the species’ range due to climate change would be valuable. Conservation efforts should prioritize forest and wetland protection, particularly in montane areas where agricultural expansion is most pronounced. Additionally, the establishment of protected corridors between fragmented populations may help maintain genetic diversity and population stability.