Reintroducing the beaver (Castor fiber) to Scotland: a protocol for identifying and assessing suitable release sites

The general problem of evaluating the potential success of mammalian reintr oduction plans has been tackled by a case study illustrating a four-phase a pproach to finding and assessing potential sites for the reintroduction of European beavers, Castor fiber, to Scotland, combining the use of Geographi c Information Systems (GIS), fieldwork and population modelling. Phase 1 us ed GIS to investigate the wider availability of habitat for beavers in Scot land, and predicted that there is the capacity to support in the order of 1 80 to 390 beaver families. Phase 2 involved the preliminary assessment of n ine sites using brief field surveys. Phase 3 focused further on the three m ost suitable sites, where a thorough habitat survey was used as a basis for calculating carrying capacities of between three and five families. Finall y, phase 4 used population modelling to assess the viability and likely spr ead of beavers following release at these three best sites. High, medium an d low parameters were derived from the literature, and populations were pre dicted to persist and spread as long as at least the medium parameters were used. This exercise illustrates the power of combining field surveys and G IS-based population modelling as a tool for planning reintroductions in gen eral, and as a foundation for planning the reintroduction of beavers in par ticular.