Density and Seasonal Movements of the Adder (Vipera berus L. 1758) in a Subalpine Environment

Abstract

AbstractWithin a study area of about 1 km2 in a subalpine dwarf shrub community in the Swiss Alps, 148 adders (Vipera berus) were marked and observed during more than six months in 1981. There was no synchronized prenuptial sloughing of males. They seemed to slough only when they had found a female. After copulation the female was guarded by the male. Adult males sloughed three times, adult females only twice or once a year. Adder density was estimated to be about three adults per hectare. Survival of adults probably surpassed 80% after three years. Displacement rate was higher in foraging adders than in pregnant females. Most neonates stayed near the birth place until hibernation. The median home range was 5.20 ha in adult males and 0.76 ha in reproductive females, when estimated with Jennrich & Turner's (1969) method. The difference was probably due to the increased distances the males travelled during the mating period. After the mating period no difference could be found between adult males and pregnant females, in distances travelled, measured as a straight line. Spacing of home ranges was absent even within sexes. Pregnant females seemed to choose microhabitats more selectively than nonreproductive females. Sites of pregnant females had a more southerly exposure than sites of nonreproductive females.