 It was hypothesised that the Orkney voles were a relict population, left behind when the land-bridge connecting Scotland and Orkney had disappeared, by the date that the more competitive "Microtus agrestis" had reached Northern Scotland.This theory has now been rejected on palaeontological, ecological, biological and geological grounds.It is now accepted that they were introduced to the Orkney archipelago by humans in Neolithic times, possibly concealed in animal fodder.