The control of grey squirrels is often advocated as a measure to conserve red squirrels. It is well known that grey squirrels typically replace local red squirrel populations within 15-20 years, and there is significant evidence that grey squirrels may be involved in spreading the 'squirrel parapox' virus into red squirrel populations. Clearly, allowing red and grey squirrels to exist in close proximity is, in itself, an unsustainable option.

Red squirrels had once been widespread on Anglesey, but numbers declined rapidly following the arrival of the grey squirrel in the mid 1960s. The 1980s saw further declines and the demise of the last broadleaved populations of reds. In the mid 1990s red squirrels were only found in two coniferous blocks, but even here grey squirrels were increasingly common.

It is believed that there were around 3,000 adult grey squirrels on Anglesey at the beginning of 1998. In contrast, red squirrel numbers had declined to no more than 40 animals, all found within the conifer plantation of Mynydd Llwydiarth. In an effort to save these last few individuals, a systematic grey squirrel control operation was started in January of 1998.

To date over 8,000 grey squirrels (including both adults and young) have been removed from woodland on the island and the red squirrel population has responded positively. By the spring of 2002 there were approximatley100 adult red squirrels on the island. Since then numbers of grey squirrels caught have gradually fallen and , as can be seen in the figure above, in 2006 less than 170 animals were trapped. This fall coincided with the project being granted access to the Hen Parciau estate in 2005, an estate were previously no trapping had taken place.

In 2006, the project was awarded £450K funding from Grantscape which has enabled the level of grey squirrel control to be greatly increased. It is anticipated that in 2008, less than 100 grey squirrels will be removed and that this will pave the way for complete eradication of the species by 2010/11.

The removal of grey squirrels from Newborough forest enabled red squirrels to be reintroduced there during 2004. However, our failure to remove grey squirrels completely from the forest led to an outbreak of squirrelpox virus in December 2006. The figure opposite shows the number of greys removed each year and indicates that only a few animals pose a huge disease risk to the red squirrels there. In the autumn of 2008 there were 150 adult and young red squirrels in Newborough, and no grey squirrels were caught.

The eradication of grey squirrels from southern coast hardwood stands has enabled red squirrels to be released there.