Wild ferrets have become a major problem for the island

Geoff Le Gallez, the only person licensed to catch the invasive non-native species, said they continue to be a major problem in Guernsey and have now spread to every parish and were affecting wild bird populations.

Native to the UK, the small predators have become established on the island over the past decade.

Mr Gallez has been trapping them on behalf of the States for the last seven years. He said he believed that originally some ferrets had been intentionally released.

‘I’ve no proof it, it’s just hearsay and it probably wasn’t illegal. People have them and can’t afford to keep them and just let them go.’

He said that males and females in season hunted for each other.

‘They can have 18 young in a single litter and even have two or three litters in a year, so you can see how it can quickly become a problem.’

La Societe land manager Jamie Hooper said that ferrets had recently been spotted at La Claire Mare Nature reserve near the coast in St Peter’s.

‘We’ve seen the reed warbler population at Claire Mare fall dramatically,’ he said.

‘We were scratching our heads for a reason, but this is probably it.’

He added that he had seen evidence of the predators near the reserve's bird hides.

‘You can smell where they have been if it’s an established group – it's a strong musky smell.

‘They are very efficient killers – anyone with chickens who have been attacked can verify that. If there is an established group here that is a very bad sign for our wild bird population, especially if they nest near or on the ground.’

States Vet David Chamberlain said the authorities knew that feral ferrets were breeding successfully because there have been many sightings of feral ferret kits.

‘If feral ferrets are predating captive poultry, they will certainly be preying on Guernsey’s indigenous wildlife,’ he said.

‘Ground-nesting birds will be at high risk as will be native mammals such as wild rabbits, the Guernsey vole, greater white-toothed shrews and presumably mice and rats.’

In 2022 a survey of Guernsey’s small wild mammal population determined that there had been a sharp fall in the population of Guernsey voles at sites across the island, other than the airport.

‘There could be other reasons for the decline in the population of the Guernsey vole,’ said Mr Chamberlain.

‘But feral ferrets certainly have to be a contender.’