While I've regularly travelled through Wales for far too many years, mostly diagonally south to north, as a borderer I've never really given much thought to deer in west Wales. I knew for instance that roe were common in the forests of Radnorshire and are I understand (possibly wrongly) that they are the most common species in the county, but I had no idea that they may have spread as far as Cardigan bay. Do you think that the present population in Carmarthenshire originated from there?
I would certainly be eager to hear more about your theory of the origins of roe in Carmarthenshire.
There's little doubt that the roe population in Monmouthshire and southern Breconshire (Powys) has expanded and extended in very recent times. I always thought that these were from the remains of a miniscule resident population plus an influx from Herefordshire and Gloucestershire.
Incidentally my daughter nearly hit a deer south or Builth Wells near Erwood last week. She was not certain of the species but thinks it may have been a fallow? Does anyone know if there are fallow in that area.