Why are there no native squirrels in Guernsey?

A grey squirrel made headlines when it arrived as a stowaway on a ferry to Guernsey - an island which has neither grey or red squirrels.

But why does the Channel Island have no native red squirrels - and why does it lack other small species like moles, badgers and foxes, as well as snakes and toads?

Dr Ellie Scopes, a population modeller for Forest Research, says Guernsey became an island towards the end of the last ice age before many small animals reached it.

"That's definitely what happened with Ireland," Dr Scopes said. "It got cut off much earlier than Britain did so has a completely different assemblage of animals."

She said some small species such as moles "could have made it over" in the past, but become extinct later.

Because Guernsey is a small island, once they went extinct locally they would not be able to re-establish themselves, she said.

Dr Scopes was part of a team that discovered the largest example of a subspecies of giant vole on Guernsey in 2018.

She said another possible reason Guernsey did not establish a population of red squirrels, which are native to Britain and France, is because they "like tree cover" and Guernsey does not have larger areas of woodland.

However other species such as field voles and common shrews could thrive on Guernsey if they became established.

Dr Scopes said a single animal, even a pregnant female, was "highly unlikely" to be able to establish a viable population because of inbreeding.

"You need quite a few to start a population," she said, potentially as many as 20 to 40 individuals.

"Very interestingly, Ireland has had a population of greater white-tooth shrews introduced recently," Dr Scopes said, adding that they are suspected to have come into the country hidden in some hay.

Guernsey and the other Channel Islands were originally joined to mainland France but broke away towards the end of the ice age, according to Guernsey Museums.

Guernsey and Alderney were separated from the French mainland about 11,200 years ago, a spokesperson said.

Herm and Sark became separate from Guernsey 2,500 to 3,000 years later.

Jersey separated from the mainland much later, around 6,000 years ago according to the island's government.

Unlike Guernsey, Jersey has a native species of toad as well as red squirrels, which were introduced to the island in the late 1800s, Jersey's government said.

Grey squirrels are native to North America and classed as an invasive species in the UK because of the threat they pose to native red squirrels.

They were first brought to the UK by the Victorians as an "ornamental species" in gardens of stately homes.

They can out-compete smaller reds for food and habitat, and some also carry a virus fatal to the native species.

Releasing greys in the UK was banned in 1930, but they have spread across England, Wales and large parts of Scotland.

Follow BBC Guernsey on X and Facebook. Follow BBC Jersey on X and Facebook. Send your story ideas to [email protected].