Polecats have been making a comeback in Oxfordshire after years of being virtually extinct. They have been seen in several parts of the county as these carnivores have gradually spread eastwards from their stronghold in mid-Wlaes.

These elusive mammals have been sighted on the Oxfordshire/Wiltshire boundary on the river Cole and also on the river Thame at Chiselhampton.

Julia Armstrong, of the Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust (BBOWT), said: “Polecats commonly enter traps set for other species and the sightings on the Cole and Thame were reported by estate managers who had set live-capture traps for mink but who inadvertently trapped polecats.

“It is illegal to intentionally trap and kill polecats without a licence and any polecats found in traps should be released unharmed.

“We did have a further record of a polecat on our reserve at Dry Sandford.”

There was also a study of polecats on the river Thames west of Oxford, which was undertaken by WildCRU, the wildlife conservation research unit of the Department of Zoology at Oxford University.

Polecats were widespread throughout Britain up until the 18th century.

They began to decline when they were hunted by farmers and gamekeepers as suspected predators of game birds.

“Polecats were also killed in the pre-Victorian and Victorian ages for their fur for clothes,” said Natalie Buttriss, chief executive officer of the Vincent Wildlife Trust, which is based at Ledbury, Herefordshire.

The trust has carried out two three-year surveys on the revival of polecats in England and Scotland and has verified their stronghold in Wales.

Polecats have been emerging from Wales thanks to changes in farming in recent years and a general upsurge in conservation.

A first survey by the Vincent Wildlife Trust (VWT) from 1993-97 found evidence of the eastward movements of the mammals.

In their second study from 2004-06 the VWT, working in conjunction with The Mammal Society, confirmed their spread into the Midlands, and it is now estimated there are 47,000 polecats in Britain.

So it is encouraging that the mammals have been located in Oxfordshire, Wiltshire, Berkshire and Buckinghamshire.

“Oxfordshire is among the Midlands counties that are seen as being the gateway for polecats to spread eastwards. The re-colonisation of polecats in these counties is seen as a natural success story that has happened without the intervention of conservationists,” said Natalie Buttriss.

VWT also found that Oxfordshire was among the counties which contained the purest polecat population, in that the county has the highest proportion of true polecats and fewer of the polecat-ferret hybrid.

One of the problems of studying polecats is that they were the originators of ferrets. Just as dogs were descended or bred from wolves, so ferrets came from polecats.

Ferrets, of course, were and still are popular among country folk hunting rabbits as they are used for flushing out rabbits from their burrows.

There is an element of cross-breeding among polecats and wild or feral ferrets that have escaped from captivity into the countryside.

However, the VWT’s most recent survey found that 86 per cent of the mammals found in England were pure or true polecats.

Johnny Birks, of VWT, reported to the Wales Mammal Conference last year, that this figure compared with 95 per cent of true polecats in Wales and 41 per cent in Scotland.

And it was also discovered that true polecats had a better survival rate than polecat-ferrets.

Polecats were first re-recorded in Oxfordshire in 1993 and were first trapped in 1996 on the same stretch of the Thames that was covered by the WildCRU study into the co-existenc of polecats, otters and the invasive American mink.

For the study, both polecats and mink were trapped and they were fitted with radio-tracking transmitters on waterproof collars. Eleven mink and seven polecats were tracked for a year by staff of WildCRU and by volunteers and, to help, transmitters were placed among tree roots, hedgerows and open fields.

Among the conclusions was that polecats and mink were able to co-exist on the Thames at that time, though perhaps not necessarily in the long term. But there was no conclusion as to whether the presence of mink affected the habitat of polecats.

One question left open — and a possible subject for further study — was whether the removal of mink by trapping would assist the revival of polecats. However, it seems encouraging that Oxfordshire is on the front line for the resurgent polecats.