The effects of microclimate factors on reproduction of the species Vipera berus berus

Adders of the species Vipera berus berus were captured at the beginning of spring and followed up during captivity with regard to their reproductive behaviour. Following parameters were examined: the length of the reproductive period, the length of copulation, the length of pregnancy, the weight of female adders before and after parturition, the number, weight and length of newborn adders. The result were compared to data obtained from a group of pregnant female adders captured at the end of August or the first days of September; thus, the longest part of pregnancy in this last group of adders took place in the natural habitat of the animals. The results of the experiment revealed a shorter length of pregnancy in adders that reproduced while captive in comparison to adders that reproduced in the natural biotope, probably due to microclimate factors, especially to temperature. No significant differences between groups were noted with regard to other reproductive parameters.