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Message: <blockquote data-quote="GDK" data-source="post: 1644166" data-attributes="member: 21712">Hi James, With regard to those two species:Red Squirrel - yes, my apologies I made a mistake there - it should be in the post 1500 list of introductions :eek!: (Now changed).  There is debate over what has historically happened to this species, but widespread agreement I think that it became at least very scarce over much of what we consider its core range today (i.e. Scotland).  Some suggest extinction in Scotland in the 1700s, others that it held on in an estate in Inverness-shire.  It also became extinct in Ireland (it was questionably 'native' there anyway).  The repopulation of this range was from introduced stock (some from England).  I dont know the situation in England and Wales, the literature always seems to be a bit vague here, but talks of large expansions in populations in the 1800s suggests a similar range/population contraction and possible introductions?  So it should be in the Cat that lists introductions on this basis.  However, it is also considered to have naturally made it across after the last ice retreat when we were still physically connected to continental Europe.  At its low ebb in the late 1700's who knows where it survived naturally.  Im sure there were places.  I have read before of complete extinction, but that is probably an extreme view put forward by (eg) Grey Squirrel fans.  More recent DNA studies on a few Red Squirrel populations in mid Wales show a very narrow lineage, suggesting a narrow ancestoral gene pool, perhaps akin to a relict population of older origins. Im not an expert and havent even read all the literature (just summarys) - so dont take my third hand as gospel, Im sure there are mistakes - have a read of the following if you can track them down:- 'Squirrels' by Shorten, M (1954)- 'A History of British Mammals' Barrett-Hamilton, GEH (1910)- summarised in 'A History of the Countryside' Rackham, O (1986)Harvest Mouse - Your guess is not too far off the hypothesis put forward for this species.  Again, no-one really knows whether it was or wasnt present naturally prior to the advent of 'modern' agricutural practices in the Neolithic period.  It was first recorded in the 1700s (Selborne) but is considered to have been overlooked prior to that.  Research has concluded that it was probably accidentally introduced with Neolithic changes in agriculture (eg transfer in Hay is thought to have been one possible conduit).  Clearance of wildwood for agriculture would help it establish and spread across its current and recent historical range, providing additional (a new?) habitat.  This species is possibly similar in colonisation to many of the archeophyte flora associated with (former!) farming practices.  Again Ive only read summarys, so there may be mistakes in this very broad overview, so to get the real research have a look at: - Sutcliffe, A.J., & Kowalski, K. 1976. Pleistocene rodents of the British Isles. Bulletin of the British Museum (Natural History) Geology, 27: 31-147- Harris, S. 1979a. History, distribution, status and habitat requirements of the harvest mouse (Micromys minutus) in Britain. Mammal Review, 9: 159-171- Yalden, D.W. 1992. Changing distribution and status of small mammals in Britain. Mammal Review, 22: 97-106.So that is why they were listed in the 'introduced' section.A few more texts that covers these things:- Macdonald, D. W. & Tattersall, F. T. (2001) Britain's mammals- the challenge for conservation. The Wildlife Conservation research Unit, Oxford University- Morris, P. (1993) A red data book for British mammals. Mammal Society- Hawksworth D L (1974) The Changing Flora and Fauna of Britain, Academic Press- Harris et al (1995) A Review of British Mammals, JNCC- Rackham O (1986) A History of the Countryside, CambridgeCheers....And another mistake in the list in post 23 is Gtr White toothed Shrew for ireland it is post 1500, for Channel Islands pre 1500 introduction.</blockquote>

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