Researchers at the Roslin Institute who cloned Dolly the sheep in 1996 are looking to create gene-edited squirrels for eventual release into the wild. This decision comes as an aim to save the UK native red squirrels from North American native grey squirrels, which have seen a decrease in number since the grey’s arrival. The Roslin Institute is partially funded by the European Squirrel Initiative, a charity dedicated to red squirrel conservation.

There are an estimated 140,000 red squirrels in the UK versus around two million greys. North American grey squirrels were imported to the UK in the late 19th century and have played a large part in driving Britain’s red squirrel population to near eradication. The red squirrels can be found in remote locations such as Anglesey, the Isle of Wight and forests in north of England and Scotland.

One major factor causing the decreasing number of red squirrels is infection from the parapox virus that grey squirrels carry. As well as this, red squirrels can only digest green acorns which are often eaten by grey squirrels, and the loss of woodland and more predators have also played a role in driving the reds to low numbers.

The researchers want to create a “gene drive” for male grey squirrels, which would make female squirrels that inherit the gene infertile. Males would be unaffected and allow them to continue spreading the gene throughout the squirrel population. The experts claim that this could completely wipe-out Britain’s grey squirrel population in the most humane way possible.

“We are investigating strategies that could humanely control the UK grey squirrel population. One is spreading female infertility.” Gus McFarlane, a researcher at the Roslin Institute, told The Sunday Times.

The researchers are also looking at ways to ensure more male babies are born than females by changing the grey squirrels’ genes. These genetic changes that the researchers propose would lead to a decrease in reproduction within the grey squirrel population and could lead to their eventual eradication, saving Britain’s red squirrels.

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