Yersin’s Forest Skink – Sphenomorphus yersini – Nguyen, Nguyen, Nguyen, Orlov & Murphy, 2018

Science name: Sphenomorphus yersini – Nguyen, Nguyen, Nguyen, Orlov & Murphy, 2018

Taxonomic:  Animalia>> Chordata>> Reptilia>> Squamata >> Scincidae >> yersini

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

Description: Physical Characteristics:

Size: The snout-vent length (SVL) of adult Sphenomorphus yersini ranges up to 56 mm.
Scale Details: It has 32-34 smooth midbody scale rows, 61-69 paravertebral scales, and 58-67 ventral scale rows. The subcaudal scales number 112, and there are 4 or 5 supraocular scales.
Distinct Features: The prefrontals are in broad contact with each other, and there are two loreal scales. The tympanum is deeply sunk, and the lamellae under Finger IV and Toe IV number 10-12 and 18-20 respectively.
Coloration: Males exhibit a striking coloration, with a black and interrupted dorsolateral line. The lateral side and lower parts of the head, neck, and tail are orange to red in males, distinguishing them from other species.
Distinctive Traits:

Sphenomorphus yersini differs from other species in its genus, such as Sphenomorphus bacboensis, Sphenomorphus cryptotis, and Sphenomorphus indicus, by the combination of its scale count, coloration, and smaller body size. The species is named after Alexandre Yersin, the famous bacteriologist, to honor his contributions to science and his association with the Hon Ba region.

Distribution and habitat: Elevation:
The species Sphenomorphus yersini, commonly known as Yersin’s Forest Skink, has been recorded at elevations of 932 m to 1162 m above sea level in Hon Ba Nature Reserve, Khanh Hoa Province, southern Vietnam.

Area:
This species is currently known only from Hon Ba Nature Reserve in southern central Vietnam. It is endemic to this area, and no sightings outside the reserve have been reported.

Habitat:
Sphenomorphus yersini inhabits evergreen montane forests. The species is found in leaf litter on steep slopes, near streams in secondary forest environments. These habitats provide the necessary moisture and cover for its survival, as the species forages on the forest floor for small invertebrates during the daytime.

Behaviour and ecology: Lifestyle:
Sphenomorphus yersini is a diurnal species that forages for small insects and other invertebrates in the leaf litter of its montane forest habitat. It is shy and relies on camouflage and the dense leaf litter for cover. The species is known to lay two eggs in tree hollows or under the leaf litter, where the moist environment helps incubate the eggs.

Conservation and status: IUCN Red List Category and Criteria:
Sphenomorphus yersini is currently listed as Data Deficient on the IUCN Red List due to insufficient information about its population size, distribution, and ecological needs. The most recent assessment was conducted in 2017.

Population Trend:
The population trend for Sphenomorphus yersini is unknown. While it is known only from a few specimens collected in the Hon Ba Nature Reserve, its population status and trends have not been thoroughly studied.

Threats:
The primary threat to Sphenomorphus yersini is habitat degradation due to deforestation, land use changes, and human activities in the surrounding areas. While the Hon Ba Nature Reserve offers some protection, ongoing forest fragmentation in other parts of Vietnam could impact the species’ habitat if it is found beyond the reserve.

Conservation Actions:
The Hon Ba Nature Reserve, where Sphenomorphus yersini was first discovered, provides a degree of habitat protection. However, no specific conservation measures have been put in place for this species, and further research is needed to better understand its ecological requirements and ensure its long-term survival.

Etymology
The species is named in honor of Alexandre Yersin, the renowned bacteriologist who discovered the bacterium responsible for the bubonic plague. His association with the Hon Ba region, where he built a research station, is commemorated through this naming.