Vipera walser

Vipera walser, the Walser viper or Piedmont viper is a viper endemic to the western Italian Alps. While long considered as an isolated population of Vipera berus, molecular analyses have shown it to be a distinct species related to the Vipera ursinii-complex.

Morphology

Morphologically, Vipera walser closely resembles the far more widespread Vipera berus. It differs in having a higher number of cephalic scales and more frequently shows fragmentation of the cephalic large shields. Additionally, most individuals possess 1.5 to 2 rows of subocular scales at both sides of the head, while Vipera berus usually only has a single row. Colouration is highly variable, with some specimens possessing a typical dorsal zigzag pattern, and others with a reduced pattern of horizontal bars. Additionally, melanistic individuals exist.

Geographic range

Vipera walser is limited to a small area in northern eastern Piedmont in the italian western Alps, with two disjunct populations, southern population of ±225 km² confined to an area of just 500 km² north of Biella and northern population of ±45 km² in the upper Valsesia.

Ecology

Vipera walser occurs in open habitats at an altitude of 1300-2300 m in valleys with high precipitation. It is mostly found on gentle south-oriented slopes with low forest cover.

Threats and conservation

Due to its recent description, Vipera walser has not yet been evaluated by IUCN, although the original species description argues that the limited extent of occurrence warrants a classification as 'endangered'. Fragmented habitat, decline in agropastoral landuse, culling and collection pose short-term threats, while in the long term climate change may alter the distribution. Additionally, low genetic variability may make the species even more prone to disturbances.