I am a bit of an anorak when it comes to deer distribution and I was really looking forward to the much delayed publication of the results of the BDS Deer Distribution Survey 2011 that finally appeared in the Winter edition of "Deer" recently received. I was disappointed to see what might be a major error in one of the maps which, if not an isolated instance, throws a lot of the records into doubt. I should say right from the start that I am not blaming the BDS as I am guessing that they just collate reports and don't validate them but if you look at the map for sika you will see that something remarkable has apparently occurred.
In the 2007 there was not a single 10km square in Wales with sika present. There were some deer on the Teifi estuary that were believed to be sika x red hybrids and were recorded on the 2007 map as reds but no sika were recorded. On the 2011 map there are now two populations of sika in SW Wales where there were none before and normally this might be the cause for celebration with some stalkers but a closer look reveals that their range almost exactly mirrors the range of the reds in that part of the World. This begs the question of whether two new populations of sika have managed to appear from nowhere and then cover eleven 10km squares in four years or have the recorders been mistakenly reporting reds as sika. The latter seems a much more likely explanation which, if true, means that many more of the reports of deer being present in new areas, especially in new areas well removed from the nearest similar population, may also be incorrect. I have asked BDS for their view but they seem to be very tardy in responding to emails.