Developing red squirrel re-introduction techniques for use during regional grey squirrel eradication programs in Europe

Summary

The red squirrel (Sciurus vulgaris), Least Concern globally but displaced across the UK by the invasive grey squirrel through competition and squirrelpox disease, was the subject of a sequence of translocation trials in Dorset, Conwy and Anglesey that progressively developed workable reintroduction methods. An early 1993 Dorset trial released 14 radio-tagged wild squirrels into pine woodland to study survival alongside greys; most died within months, with foxes and squirrelpox among the causes, marking it a failure but yielding valuable data on inter-species competition. A 1990s Conwy trial in broadleaved woodland established a captive-breeding population and successfully bred wild young, but squirrelpox eventually caused local extinction, making eradication of grey squirrels, not just population control, an essential precondition for future releases. Building on these lessons, Anglesey combined a wider grey squirrel eradication campaign begun in 1998 with staged captive-bred releases, first into the 689-hectare Newborough pine plantation and later into broadleaved parkland and gardens starting in 2006-2007, using small founder groups, shortened captivity periods, fecal virus screening and woodmouse removal from enclosures to curb adenovirus and squirrelpox transmission. The Anglesey population grew from 80-90 adults in 2002 to around 700 today, the largest and most genetically diverse in Wales, supported by over 150 volunteer-run feeding stations and a citizen-science reporting network, with red squirrels dispersing naturally across the Menai Strait to the mainland by 2009. The project rates the two early trials as failures but the resulting Newborough and broadleaved Anglesey reintroductions as successful, crediting habitat-matched release protocols, disease-management measures developed from earlier failures, and strong community engagement.