A key issue in ecology is to understand the dynamics of metapopulations.
Fragmentation exposes each group to the risk of random extinction.
Consequently, colonisation and dispersal between groups play an important role in determining the persistence of metapopulations. However, these processes are extremely difficult to estimate using field methods alone. Water voles live in small separate groups along river banks and in patches of good habitat in uplands. In Cairngorm, colonisation and dispersal operate among populations in adjacent tributaries, but the spread of American mink upstream of Braemar has created a barrier between tributaries. This study will generate new insights into the dynamics of fragmented populations, and provide useful guidelines for the conservation of the water vole and other species.