species of the week #87 – asp viper

Germany’s forests are getting darker, did you know that? Nitrogen input from the air fertilises areas that are actually free of trees and bushes. As a result, blackberries and other nitrogen-loving plants are colonising the forests. Because of the (actually sensible!) renunciation of large clear-cuts, there are also fewer sunny areas in the forest. Light species such as the asps viper, which lives on sunny, exposed rocks, are increasingly losing habitat. The asps viper has been declared a forest target species in its last remaining German habitat in the southern Black Forest. The target species is the species whose needs are to be taken into account in forest design.

Besides the adder, the asps viper is the second venomous snake species in Germany. Its venom is not lethal to humans, as is the case with the adder. Asp vipers are very varied in colour, from grey, brown and beige to yellowish or reddish, there are many colour variations and colour gradients. In the alpine region, completely black specimens can be found. As a rule, asps show a characteristic black dorsal pattern consisting of two rows of alternating dark bars. An often dark brown temporal band runs from the eye to the neck. To distinguish asp vipers from vipers, look at the dorsal markings and snout region. Adders carry a zigzag band and have a pointed snout, the dorsal markings of asp vipers almost always show unconnected spots and they have a snub nose. Asps only reproduce every two to three years. Females mate with several males in autumn, after which the female stores the sperm in a sperm pocket. After ovulation, fertilisation and a gestation period of about 12 weeks, up to 15 young are whelped, which hatch from their egg cases during or after birth.

The asps viper is one of the few forest target species. Target species, which are representative of other species due to their ecological requirements and on which promotion measures can be focussed, can have important functions for the functionality of a landscape and represent its biological diversity, or they can also be representative representatives of certain habitat types. Endemic occurrences can also be classified as target species. Baden-Württemberg harbours the only autochthonous asps in Germany, presumably a relict occurrence that was associated with the occurrence in the northern Swiss Jura during a post-glacial warm period. The population of about 240 animals has been scientifically monitored since the 1980s and is considered stable. The nearest occurrence is a good 20 km away in the Swiss canton of Aargau. Bordering the Saarland, there are further occurrences in the French Lorraine between Metz and Thionville, which, however, all settle on the left side of the Moselle. The occurrences at Grenzacher Horn near Basel and near Lörrach are considered extinct.

Factors threatening the habitats are shading, which leads to a changed microclimate, and disturbances. Currently, attempts are being made to connect the individual rock piles in the southern Black Forest with tree-free corridors through targeted thinning. Due to its low dispersal rate, the Asp is severely threatened by habitat fragmentation. In Switzerland, its decline is attributed to the intensification of agriculture and increasing building development. Individuals also repeatedly fall victim to road traffic.

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Image: By Bernard DUPONT from FRANCE – Asp Viper (Vipera aspis) male (found by Jean NICOLAS), CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=