Grey Squirrel - Sciurus carolinensis
Introduced into parks and gardens in the late 1800's it adapted quickly and has spread throught England Wales and southern Scotland. It can be found in most parks and woodland in England and Wales but is abscent from most of Scotland and some parts of Northern England. The black form is now well established in Beds, Herts and Cambs.
Sika Deer - Cervus nippon
Introduced in 1860 into parks in Dorset a large population has grown and is common in Dorset. Other populations exist as on Lundy and in Scotland.
Arne RSPB has a large and confiding population.
Muntjac - Muntiacus reevesi
Introduced as an ornamental deer to Woburn park it has escaped and bred readily in the wild. It has spread widely in south England and into the midlands.
Can easily be found in most woodland.
Chinese Water Deer - Hydropotes inermis
Introduced in the late 1800's to Whipsnade and Woburn. Escaped animals have spred east and the population is slowly increasing it prefers fens and boggy woodland.
Found only in East anglia and the eastern midlands.
American Mink - Mustela vison
Released from fur farms in it has been present since the 1960's and has spread far and wide and had a devistating impact on native wildlife. They can be seen on many waterways.
Feral Goat - Capra hircus
A mixture of wild and escaped domestic stock, they can be found in Snowdonia, many places in Scottish Highlands particularly the west coast and Loch Lomond, Lundy, Valley of rocks, Devon, Cheddar Gorge, Great Orme, Mull of Kintyre, Portland, Jura.
The findhorn valley and the mine at Dinorwic, Snowdonia are good sites.
Red Necked Wallaby - Macropus rufogrieseus
Escaped from Zoo's these marsupials have persisted in small colonies, helped with mild winters their numbers have risen but are still small.
Populations are present on the Isle of Man (the largest), Loch Lomond and around a few around Woburn.
Ferrett - Mustela furo
A few thousand persist on many of the Scottish islands, derived from escaped pets, there are also small numbers widespread through the UK.
Wild Boar - Sus scrofa
Probably should go in the reintroductions section, althought the animals were not released as part of a programme of reintroduction but were escapes from farmed animals. They were hunted to extinction in the 1700's
Good populations exist in Exmoor, Sussex and the Forest of Dean.
Black Rat - Rattus rattus
Accidentally introduced from shipping and were common around docks, indeed recent signtings from Cornish docks are recent travellers. The only self sustaining population is now on the Shiant Island in Scotland which is being exterminated, the Lundy population was exterminated a few years ago.
The Sark in the Channel Islands is the only place to see black rats in the British Isles.
Edible Dormouse - Glis glis
Introduced as far back as the romans for food the edible dormouse, it has only become established since the early 1900's when it was introduced into Tring park in Hertfordshire. They have not spread more than 50 miles from the original site as the habitat is isolated.
Black Tailed Prairie Dog - Cynomys ludovicianus
A small population is established in Northern Ireland, but as of 2010 has been eradicated, scattered indi.
Feral Dog - Canis familiaris
Widespread mainly in urban areas, although decreasing due to increased capture.
Feral Cat - Felis Catus
Widespread mainly in urban areas, more particularly in industrial / waste areas
Coati - Nasua nasua
A small population existed in the Lake District, they were present for several years but have not been seen for a couple of years.
Siberian Chipmunk - Tamias sibiricus
Commonly kept in zoos and as pets. Several small colonies have been founded all now eradicated, the last where they may still persist is in Berkshire although a trapping scheme was / is in place, but it is assumed they still persist in some sites with occasional sightings.
Raccoon - Procyon lotor
I have had little success in finding out about Raccoons in the UK there have been many escapes and rumours of breeding, the only confirmed breeding was in South Yorkshire and Somerset. One population persisted for four years before capture. There are scattered individuals present in the UK.
Coypu - Myocastor coypus
Escaped from fur farms in the 1930's and established themselves in East Anglia and the Norfolk Broads in particular, harsh winters had kept them in check but mild winters allowed the population to increase. An eradication programme sucessfully removed them by the early 1980's.
Muskrat - Ondatra zibethica
Escaped from fur farms in the early 1930's and established themselves in the Shrewsbury area and some parts of Scotland, an eradication scheme removed them fairly quickly by the end of the 1930's.
Mongolian Gerbil - Meriones unguiculatus
Commonly kept as pets it is no surprise that small colonies of these animals have been present in the UK, the largest and most persistant was a colony on the Isle of Wight which lasted for some years in the 1980's. Currently there are no major colonies.
Himalayan Porcupine - Hystrix hodgsonii
A small population was established in South Devon after escape from a wildlife park, breeding occured and the population increased they have now been removed but persisted for over 10 years in the 1970's. There are rumours of others possibly in Stoke or Wiltshire.
Golden Hamster - Mesocricetus auratus
Again kept as pets and many populations have come and gone, the largest was established in North London in the 1980's it persisted for some years and spread over a reasonable area. Currently there are no major colonies.
Crested Porcupine - Hystrix cristata
A few porcupines escaped in Staffordshire in the 1970's and a small population existed for several years before they disappeared, their fate unknown.
Striped Skunk - Mephitis mephitis
A small colony exists in the Forest of Dean, several sightings, photographs, CCTV fotage, a corpse and even a live animal capture, give real evidence to support this. Skunks can easily adapt to the UK climate conditions and are surprisingly commomly kept as pets. These are thought to be released pets, because since 2007 it has been illeagle to remove the scent gland making them less attractive as pets. Indeed I visited the site and found a skunk in 2009. There have been no sightings since 2013.
Greater White Toothed Shrew - Crocidura russula
Introduced to Co Tipperary, Ireland but it is not know when, only discovered in 2008 from owl pellet analysis. Their range is incresasing.
Bank Vole - Clethrionomys glareolus
Introduced into Southern Ireland in the 1950's it is now quite widespread.
Semi Wild / Free Ranging Species
Geoffroy's Marmoset - Callithrix geoffroyi
Free Ranging in South Lakes Wildlife Park
Common Marmoset - Callithrix jacchus
Free Ranging in Woburn Wildlife park