Genetic monitoring of a founder population of brown bears (Ursus arctos) in central Austria

Abstract

The small population of brown bears in central Austria originated from a single migrant bear that had settled in the area in 1972 and three bears that were released in the years 1989–1993. Subsequently, the population has been monitored by radio-tracking and collecting data on bear signs and observations. In 2000 we started a genetic monitoring program of the population with the aim to obtain data on population size, sex ratio, relationships as well as movements of individuals. We present results from six years of genetic monitoring, which were combined with field observations. During this time 1,005 hair and faecal samples were gathered in an area of >3,000 km², most of them in the core area of <1,000 km2. Furthermore we analysed blood samples from captured individuals. Eight microsatellite and two sex determination loci were employed for DNA profiling. The number of detected individuals is surprisingly low, ranging from 5–8 per year. Concerning relationships the analysis reveals that all genotyped individuals are descendants of the founder individuals indicating that no immigration took place. Only one male and three females (mother and 2 daughters) took part in reproduction. Considering the fact that 28 bears were born in this region since 1991 the question arises where the bears disappear to. Our results suggest that subadult bears migrate from the core area. However, indices of bear occurrence outside the core area are rare and migration could be proved only for two young males. Other explanations, such as increased natural mortality and illegal hunting are discussed.