Truong Son Pit Viper – Trimeresurus truongsonensis – Orlov, Ryabov, Thanh & Cuc, 2004

Science name: Trimeresurus truongsonensis – Orlov, Ryabov, Thanh & Cuc, 2004

Taxonomic:  Animalia>> Chordata>> Reptilia>> Squamata >> Viperidae >> truongsonensis

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

Description:

Physical Characteristics:

Size: Males can reach a snout-vent length (SVL) of 521 mm, while females are slightly larger. The total length (including tail) of males can extend up to 642 mm.
Scales: 166–175 ventral scales, 65–69 pairs of subcaudals, and 21 scale rows at midbody. The scales are strongly keeled, with the exception of the first row of dorsal scales, which have barely noticeable keels.
Distinct Features: The head is small, triangular, and clearly distinct from the neck. It is covered by small, granular shields. The supralabials number 9–10, and the infralabials number 11–12. The rostral scale forms an isosceles triangle with a truncated top, and the species features a forked hemipenis with large and small spines.
Coloration and Appearance:
Males of the species are predominantly greenish-blue with red-brown bands running across the body and tail, while females have a more muted light-brown color. The belly is gray-bluish, and the red-brown spots on the head form a mosaic pattern. This distinct coloration pattern makes the species easily recognizable.

Distribution and habitat:

Elevation:
The Truong Son Pit Viper (Trimeresurus truongsonensis) is found at elevations ranging from 500 to 600 meters above sea level. Its type locality is within Phong Nha-Ke Bang National Park, in the Quang Binh Province of central Vietnam, in the Annamite Mountains.

Area:
This species is endemic to central Vietnam, and its range may extend beyond the type locality in Quang Binh Province to the neighboring Quang Tri Province. The species is estimated to have an extent of occurrence (EOO) of approximately 2,340 km². While there is speculation that it may occur in Laos, no confirmed records exist.

Habitat:
The Truong Son Pit Viper primarily inhabits evergreen tropical forests in the Annamite Mountains. The species is known to be partially arboreal, and individuals are often found basking on mossy karst rocks under the branches of trees and shrubs, typically after strong rainfall. They tend to avoid direct sunlight and high temperatures, preferring to remain in karst crevices or tunnels when not active.

Behaviour and ecology:

Lifestyle:
This species is secretive and often timorous, retreating into karst crevices when it senses danger. It is mainly active after strong rains and is commonly found basking on moss-covered rocks in shaded areas. The Truong Son Pit Viper is rarely found on the ground, preferring to remain within the safety of the karst crevices and tunnels.

Reproduction:
The species is ovoviviparous, meaning the eggs develop inside the female, and the young are born live. Specific reproductive details, such as clutch size and breeding season, are not well documented.

Conservation and status:

IUCN Red List Category and Criteria:
The Truong Son Pit Viper is listed as Endangered under criterion B1ab(iii) on the IUCN Red List, primarily due to its limited distribution and the ongoing decline in habitat quality.

Population Trend:
The current population trend is unknown, and the species is thought to be rare, with limited observations.

Threats:
The species faces significant threats from habitat destruction, including logging and agricultural expansion. The potential for exploitation for the pet trade also poses a risk to this species. Additionally, forest degradation within its range, including in Phong Nha-Ke Bang National Park, continues to diminish the extent and quality of its habitat.

Conservation Actions:
No specific conservation actions are currently in place for Trimeresurus truongsonensis. However, the species’ presence in Phong Nha-Ke Bang National Park provides some degree of habitat protection. To ensure its survival, further conservation efforts and habitat preservation are necessary.

Etymology
The species name “truongsonensis” refers to the Truong Son Mountains (also known as the Annamite Mountains), where the species occurs. This emphasizes the geographical importance and the species’ connection to this mountain range.