- Published: 03 April 2015
The common adder (Vipera berus) belongs to the family Viperidae. Its distribution range is among the largest among all reptiles: its spreads from the Atlantic to the Pacific, and from the Arctic to Greece. Despite the fact that it occupies such a vast areal, the adder’s populations are mostly declining, often due to various anthropogenic influences on the species and its habitats.
Particularly vulnerable are the adder populations present in the Balkans, designated as the V. b. bosniensis subspecies (the Bosnian, i.e. Balkan adder). This subspecies is usually thought to inhabit exclusively high mountains; it is less known that it also occupies lowland regions, usually along large rivers.
Very little is known about the lowland adder populations, not only in Serbia, but in other countries as well. According to the available literature, they can be found in the vicinity of the Obedska bara wetland, and on the Fruška gora and Vršački breg Mts.; at the beginning of the XX century they were apparently present on the Avala Mt. South of the Sava and Danube rivers the adder inhabits hilly and mountainous areas: it was found on the Kopaonik, Stara planina, Šar-planina and Prokletije mountains, on the Vlasinska visoravan plateau, and in several other highland places.
The lowland adder populations usually occupy comparatively cold and moist places around the autochthonous, old forests of the pedunculate oak (Quercus robur), and near wetlands. These areas are increasingly threatened with urbanization, deforestation, expansion of agricultural areas, climatic changes and other, natural and anthropogenic processes and influences. Adder populations in the above-mentioned lowland localities are virtually fully isolated from each other, being separated with vast areas of arable land and human settlements. Such isolation of small populations poses serious threats to their survival.
The adders are usually 50–70 cm long. Males are typically greyish and females brown or reddish, with distinct dark zig-zag pattern along the back. In the Balkan adders (the bosniensis subspecies), this zig-zag line is often broken. Some adders are completely black (melanistic), but there are also light brown patternless (concolor) specimens. The adders are characterized with a row of white scales on the upper lip/jaw (supralabialia); on their nape there is a V- or X-shaped pattern. Among the larger scales on the head, the largest are frontal and two parietals. The head is elongated, oval. Dorsal scales are ridged. As in other vipers, the tail of adders is short compared to trunk; it is longer in males than in females. As in other vipers, the pupil is vertical.
The cold period of the year (between October–November and March–April) the adders spend in the state of dormancy, the so-called winter sleep (hibernation). In spring the males emerge first, and two to three weeks later the females begin to appear; shortly afterwards, the snakes engage in mating. As other European vipers, the adder is viviparous: it does not lay eggs, but gives birth to fully formed young. At least in the montane populations, adder females reproduce bi-annually. They can deliver 3–18 young, each 13–15 cm long and not heavier than 3 grams.
The adders are comparatively secretive hence people rarely meet them in nature. When encountered, the adders try to flee and escape contacts with people: a man is not their prey, and the snakes never attack unprovoked. Like other snakes, an adder can attack a man when it feels threatened: if accidentally stepped on, or if a person tries to catch it.
The adder’s venom is efficient for subduing small animals: its effects on men are usually weak. In the case of adder’s bite, people experience pain, redness and swelling develop, as well as dizziness, problems with digestion, nausea, diarrhoea and similar effects; complications seldom occur, and fatalities are exceptionally rare.
Adders feed predominately on small mammals, amphibians, other reptiles, and on birds, occasionally. In their diet various rodent species predominate, therefore these snakes are very important in ecosystems: they present a natural mechanism of rodent abundance regulation (chemicals used to eradicate these pests – rodenticides – are toxic for people as well). It is a well-known fact that rodents are transmitters of numerous severe infectious diseases, and they can seriously damage the crops/harvest (from 20–30%, up to 100% of damage in the years of rodent calamity): in other words, they have both economic and health impacts on people. Bearing this in mind, the adders should be considered as the men’s allies.
In Serbia, the adder (Vipera berus) is listed as a strictly protected species. Nevertheless, disregarding such high level of formal protection, in practice this species is exposed to numerous threats.
Influences which most seriously threaten adder populations and their habitats:
- occupying adder habitats by expanding areas under arable land;
- excessive application of pesticides in agriculture;
- unplanned/total deforestation, cutting of old oak forests and replacing them with poplar plantations;
- intentionally lit and incidental fires in the adders’ habitats;
- killing of individuals;
- collecting and taking the adders out of their natural habitats.
Like numerous other species, adders prefer the so-called mosaic habitats, landscapes with forests, water bodies and open spaces. Tree plantations or forming of large areas under single culture lead to disappearance of habitats suitable for wildlife, and are often almost sterile.
Protection of the adder and its habitats offers, at the same time, prerequisites to conserve other rare and endangered animal species; therefore, the activities scheduled within this project shall have manifold implications for nature, but for men as well.
Detailed field searches for the Bosnian adder populations shall be performed in suitable lowland habitats in northern Serbia (the Vojvodina province). Our intention is to obtain precise data on their current distribution, levels of mutual isolation, and threats to which this strictly protected species is exposed. We shall collect the basic population information (population sizes and densities, sex ratios, age structures): these shall serve as the foundation for future studies, and as the basis upon which we shall propose conservation and monitoring activities. Basic morphological measurements shall be recorded which will enable the comparisons of lowland Bosnian adders in Serbia with populations of this species in other parts of our country, and in several other Balkan countries.
Along with field research activities, we shall establish contacts with local schools, farmers, forestry services, and authorities, and give them talks and presentations concerning adders, their roles in natural and human-altered ecosystems, and potential threats to humans. One of our primary aims is to reduce fear and break the prejudices which surround vipers (and snakes in general): we will explain the basics of snake behaviour, and present the data from publications concerning the incidence and severity of snakebites (available for several European and Balkan countries). We shall highlight the importance of adders in agroecosystems, as natural regulators of rodent populations. Also, we shall emphasize the need for maintaining the mosaic structure of habitats and for preservation of the remaining corridors between suitable habitat patches: these are under severe pressures from the already existing and newly proposed monoculture plantations in the Vojvodina province. Printed educational materials, covering main themes of the project, shall be provided for all target groups.
Main aims of the project are:
a. to check the presence of lowland adder populations in the known (published) and potentially suitable unknown localities;
b. to list all threats the lowland adder populations are exposed to, and consider necessary conservation measures;
c. to obtain, wherever possible, basic adder population parameters;
d. to educate local inhabitants, managers and decision-makers of the need to preserve this snake species and its habitats, in order to ensure the background for future local management plans.
For further information contact:
Rufford Website: http://www.rufford.org/projects/aleksandar_simović
Project site: http://www.berusbosniensis.shdmr.org