The records of Albino Snake, partial albino, and leucistic individuals among four species of European Viperinae (Vipera ammodytes, Vipera aspis, Vipera seoanei, and Vipera berus) were summarized based on literature records, museum material, reports of field herpetologists and herpetoculturists, and a short description of all reported specimens was made. For the first three species only scattered observations have been made, whereas at Vipera berus these defects proved to be more widespread, and present an occurrence pattern shift to the Nordic countries.
Albino Snake might have a higher survival chances also due to higher population densities in the north. The number of snakes per habitat unit seems to be higher in the northern parts of the species range: e.g., 3 individuals per hectare in Dischma valley, SE Alps, Switzerland; 0.99 to 4.00 individuals in different populations of Western Germany (Biella et al., 1993); up to 6 individuals per hectare on the Island Stora Hästholmen, southwestern Sweden (Andrén and Nilson, 1983). Still this number is highly dependent on food availability and weather conditions (Andrén and Nilson, 1983; Forsman and Lindell, 1991; Lindell, 1997). As adders are subjected to high predation pressure by avian predators, it might be possible even for an albinistic or leucistic individual to hide from a predator due to the movement of many snakes at its approach.
The albino Snake individual observed for V. seoanei, the fourth European viperin species where the color defects was observed, intimates a more widespread occurrence of the mutation, which probably is present for all European species, but for most of them is rare and has not been recorded yet.
The offset occurrence pattern of these color defects for V. berus specimens raises several questions which have to be answered and research on the topic has to be carried out. The albino Snake state seems to be was widespread in the population at Riihimäki, and if this mutation is still preserved there, this population might serve as a test locality for the hypotheses.