Reptiles & Amphibians of France - Orsini's viper, Vipera ursinii

Orsini's viper, Vipera ursinii
(Bonaparte, 1835)

History and origin
The Orsini's viper was first described by Bonaparte in 1835, the scientific name of this species is Vipera ursinii, Vipera meaning viper and ursinii, this name comes from a certain Mr Orsini who dicovered this species in 1833, Bonaparte named this species after him.

Characteristics
They are characterised from other vipers by their small size and rounded head.

Description
=Size=
They are born at around 12 cm long, averaging about 30 - 40 cm long growing up to sometimes up to 50 cm long.
=Morphoology=
They are very short, robust with a small rounded head, keeled scales and vertical pupils. Their nose appearance, eye size, scales counts are all variable and are the reason of many subspecies having been described.
=Patterns & colours=
The pattern is quite stable in this species. They are usually grayish or light brown with a dark zigzag pattern. The flanks are usually slightly darker with various often vague blotches and markings. They have a darker line running from the eye backwards. Their belly is dark.

Geographical range
A highly fragmented distribution of many isolated populations in central Italy, southeastern France, Croatia, Greece, Bosnia, Montenegro, Romania, Hungary. Extinct in Austria and most likely also in Bulgaria. Populations from the Ukraine are now considered as Vipera renardi, those of the Danube river delta in Romania, are of questionable attribution.

Subspecies
- graeca - Found in Greece; Mountain form. It has several enlarged supralabial scales.
- macrops - Found in western Balkans in a few countries; Mountain form.
moldavica - Found in Romania; lowland form.
- rakosiensis - Found in Hungary, Romania (recent rediscovery) and formerly in Austria; lowland form; gives birth to about only 11 young.
- ursinii - Found in Italy and France; Mountain form; gives birth to only about 4 young.
Animals from the Danube river delta (Romania) are of uncertain (sub)species rank and might belong to the eastern Vipera renardi, formerly a subspecies of Vipera ursinii. Other related (sub)species live further east.

Sexual differences
Females are larger then the males, especially in late spring when they carry their young.

Seasonal variations
None.

Diet
They mainly eat insects, like larger crickets and grasshoppers but also lizards.

Defensive habits
They are usually said to be very placid and docile, rarely biting, but they might also be fairly aggressive and may bite. They often hiss and attack with their mouth closed.

Reproduction
Breeding occurs when the snakes wake up from hibernation in spring, a week after, they are all looking for each other and mating begins. The female carries around with her about 6 young (extremes of 3 to 20, depending on subspecies, see above). They are born 4 months after being conceived.

Sexual maturity, life span
The average life span for Vipera ursinii is unknown, it is also not well know when they reach sexual maturity, but possibly in their fourth year.

Habits
Active by day, they are easily observed early in the morning (during the first couple of hours of sunshine). In areas of its range without too much of human impact (for ssp. ursinii), they may be very common, sometimes with as much as 15 to 25 specimens per hectare.

Venom
The venom of the Orsini's viper is less potent than that of any other European viper. Due to its small size, weak venom and its acclaimed calmness, this viper is considered to be the least dangerous of Europe.

Habitat
Habitat type differs between subspecies. Mountain forms (ursinii, macrops and graeca) are found over 1000 m and sometimes no lower than 2700 m. On dry hillsides with some vegetation, often very scarce (e.g. dwarf juniper bushes). Other subspecies are lowland forms, living in dry meadows.

Predators
Their natural predators are birds of prey and mammals. Some competition with other vipers, like Vipera aspis, seems to explain in part their limited current range.