BY BRENDAN ANDERSON

This is what happens when greys come into contact with red squirrels. It can take up to 14 days to die and the pain is unbearable – a very slow death. If we cannot stop this, there is no hope for the reds.

Best estimates state that the greys currently stand between 2.5 and 2.7 million whereas the reds number a mere 140,000.

Why we have to keep culling the Grey Squirrel in the UK and Ireland

Before the grey squirrel (Sciurus carolinensis) arrived in the UK and Ireland, the red squirrel (Sciurus vulgaris) was the only UK native squirrel. They evolved with and flourished alongside Britain’s native flora and fauna and were therefore suited to our climate and conditions.

While habitat loss and fragmentation impacted red squirrel populations, the introduction of the Grey squirrel in 1876 had a devastating impact. Greys compete with reds for food and also carry a virus known as squirrel pox.

While greys are immune to the disease, red squirrels are not. When grey squirrels come into contact with reds, they can transfer the virus, which results in death within a couple of weeks.

Adenovirus is another significant risk to red squirrels and is transmitted by grey squirrels.

Garden bird tables and feeding areas in locations where both red and grey squirrels are present result in disease transmission.

Red squirrel populations can only survive and thrive in the absence of grey squirrels so it is imperative that buffer zones are maintained and extended around existing red populations.

Bark stripping 

Grey squirrels strip bark from trees to get to the sap in the layers underneath.

While red squirrels also exhibit this behaviour, populations are so low, this does not pose an issue as it does with greys.

When a tree is damaged in this way, sap is prevented from flowing up the trunk to parts of the tree above the damaged area.

Ringbarked trees will usually die or be so badly damaged that their timber value is drastically reduced.

Over the years the government has spent millions on grants for tree planting, but unless the grey squirrel is controlled new trees will not last more than 20 years and will be of little commercial value.

Effects on Wildlife 

Grey squirrels eat a varied diet, much the same as the diet of the red squirrel, but they can digest tannins more easily than red squirrels so will often eat acorns and other tree nuts before they are ripe, which results in less food for native red squirrels and other wildlife. This can have a negative impact on the reproductive success of red squirrels and other wildlife.

Grey squirrels have also been known to predate on song bird chicks and eggs and there is evidence to suggest they may raid nests of dormice and hedgehogs and eating the young and possibly when hibernating and even Bats.

This is being investigated by Andjin Siegenthaler at Salford university, who are conducting DNA analysis of grey squirrel stomach contents.

Research by GWCT shows the presence of grey squirrels in a woodland reduces songbirds by an average of 15%

Property damage

Grey squirrels can damage your house if they get into your roof space.

This is an issue faced in many other countries, where timber, cables and pipes can be damaged by nesting squirrels.

Your house will not be insured for squirrel damage so if your house burns down you will lose everything. Outbuildings are also put at risk.

Health and safety

Increasing contact between humans and their dogs and grey squirrels in urban areas such as gardens and city parks can increase disease transmission, particularly in areas where people feed squirrels by hand. They are a public Health risk.

Squirrel diseases that humans can catch include:

• Salmonellosis.
• Lyme disease and other tick-borne diseases.
• TB
• Tularemia.
• Leptospirosis.
• Rabies.
• Bubonic Plague (Black Death) Some Grey squirrels in the USA have been found to carry this disease.

Why control can be effective

There are now an estimated 3 million grey squirrels in the UK and red squirrels could be extinct within the UK in the next 10 years.

Control of grey squirrels is therefore essential.

Natural solutions such as pine martens, which predate on squirrels, have been shown to reduce grey squirrel numbers in areas where both red and grey squirrels are present.

Grey squirrels have been found to be more vulnerable to predation from pine martens than reds.

This is because red squirrels evolved with pine martens and are more agile than greys.

Trapping and shooting grey squirrels is a recognised method of effective red squirrel conservation.

An oral contraception has been proposed as another way to control grey squirrel numbers in other habitats, but it is unclear when this will be introduced.

Scientists can use the powerful gene editing technique CRISPR-Cas9 to target a specific gene and make very precise changes to the DNA of plants or animals.

CRISPRs are specialised stretches of DNA, while Cas9 is an enzyme that acts a bit like a pair of molecular scissors, cutting up strands of DNA. Using this technique, scientists can remove an unwanted gene or insert a new one. With this process only males are produced so the Greys will eventually die out.

Lord Goldsmith claimed invasive species wreak £1.8 billion damage a year on UK woodlands.

Grey squirrels alone are thought to cost the UK economy around £40 million a year, due to the damage they inflict on broad-leaved forests.

There are hundreds of dedicated volunteers throughout the UK and Ireland fighting to save our red squirrels, but we urgently need more volunteers and land owners to get involved and help save this iconic species before it’s too late.

Brendan Anderson is a campaigner to protect the Red Squirrel and his Group can be accessed here.