Vipera seoanei seoanei   Lataste, 1879

Distribution and habitat:
Vipera seoanei seoanei is distributed throughout the north of the Iberian Peninsula from Galicia to Navarra and the extreme southwest of the French Pyrenees.

In Portugal it is found north of the Duero River. It inhabits an average altitude of 600 mts (2000 feet) a.s.l. although it may be found at altitudes between 0 and 1600 mts (0 – 5250 feet) a.s.l.

A combination of mild climate and high humidity, which are typical in the north of the Iberian Peninsula comprise an ideal setting for the prolific Vipera seoanei seoanei to thrive in.

The presence of this viper is associated with areas of dense vegetation, such as blackberry bushes, ferns and heather, especially if there are old stone walls in between.

It avoids dense forest due to the lack of sunlight, however, it can be found in forest clearings.

         Vipea seoanei
Vipera seoanei seoanei, Sª de Covadonga
(Asturias) - photo: Daniel Gómez

Like the rest of the European vipers Vipera seoanei seoanei inhabits areas where ferns are abundant, because these plants offer a perfect camouflage for this kind of snake. Fern leafs are very similar to the viper´s zigzag pattern, and the shadows that they project on the ground configure an optimum camouflage.

Colouration:Vipera seoanei seoanei shows four different colour morphs;

* The classic form: The ground colour is beige or grey and even reddish is some specimens.
Along the dorsum runs a zigzag band which is dark brown in the centre bordered with black bars on both sides.

These numerous black bars or dots along the zigzag stripe give the visual appearance of a “zip” along the dorsum of the body. Dark bars or blotches are also present along both sides of the body.

The “classic” form is found throughout the entire distribution range of Vipera seoanei seoanei.

Vipea seoanei
Vipera seoanei seoanei, classic form
photo: Alberto Barreiro

* The bilineata form: In this form the zigzag edges have disappeared completely and the side bars or blotches have fused together, thus resulting in an overall uniform dark colouration with two thin parallel stripes of lighter colour running along the dorsum.

Surprisingly, these twin stripes are the remainders of what once was the ground colour.

The males of the bilineata form can be black with either yellow, orange or cream stripes, or can be dark brown with either grey or cream stripes.
Females are less colourful than males; usually they are brown with yellowish stripes. This form is most abundant in the north of Asturias.

Vipera seoanei
Vipera seoanei seoanei, bilineata form - photo: Daniel Gómez

Vipera seoanei
Vipera seoanei, unicolor form - photo: Raúl Doblado

* The uniform or unicolor form:

Specimens of this form don’t have a dorsal pattern.
They exhibit an overall uniform colouration which is usually coppery-brown or olive-brown. This variety is relatively rare.

Vipera seoanei
Vipera seoanei seoanei, melanic form - photo: Daniel Gómez

* The melanic form:

These are the black coloured specimens.
Melanic specimens may be found throughout the entire Seoane´s viper´s distribution range and they represent a significant percentage of all the specimens in the different populations.

Head: Both male and female specimens frequently exhibit a marked head ornamentation. The two oblique markings which form the typical inverted “V” are always present.
The frontal scale is present in most of the Vipera seoanei seoanei specimens and the parietal scales are quite frequently also present. There are two apicals and two canthals on either side of the head. Most specimens have one single row of scales between the eye and the supralabials.

Pholidosis: Vipera seoanei seoanei has 21 (rarely 19 or 23) rows of dorsal scales along the body. All of the dorsal scales are keeled except for the first row on either side of the body. Males have between 122 and 144 ventrals, the average being 136,3 ventrals. Females have between 132 and 145 ventrals, with an average of 137,4. There are 30 to 40 paired subcaudals in males and 27 to 33 in females. The average number of subcaudals is 37 for the males and 29,8 for the females.

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