This is again from the latest Current Archaeology:
Red deer reached Britain about 10,000 years ago as ice sheets withdraws, but they did not reach the Orkneys or Outer Hebrides for another 5,000 years. But recent genetic research shows the two groups were not genetically the same. More intriguingly, the deer DNA from Orkney and the Outer Hebrides did not match ancient samples from the next nearest likely sources of Ireland or Norway, so it seems they may have come from somewhere on continental Europe.
The deer are not alone: other species have also unusual genetic sources, such as the Orkney vole which arrived from Belgium c5,000 years ago.
This suggests that there was movement between the Scottish islands and Europe during this period. As in the case with the vole, the high genetic diversity seen in Neolithic deer remains from Orkney and the Outer Hebrides suggests that large numbers of individuals had been moved to establish the new populations.
I’m starting to wonder if there’s a Disney film in this odd story.