Ferrets are domesticated polecats, so yes, polecats can and do breed with feral ferrets – and have done for centuries.
Breeders have also ‘back-crossed’ domestic ferrets with wild polecats to produce a variety of colours. (Some ‘ferrets’ can be distinguished from true polecats with certainty only by genetic analysis.)
As a result, a confusing mix of ferrety polecats lives alongside true polecats in the British countryside, reducing the overall purity of the wild population.
The occurrence of ferret genes among our polecat population may not, though, represent a threat, and may even be advantageous in increasing genetic diversity.
Polecats suffered a catastrophic decline during the 19th century, after which the population was almost entirely restricted to a stronghold in mid-Wales.
Hybrids occur mostly at the edge of the expanding polecat range, and true polecats appear to outcompete hybrids in the long term.
There is also no clear evidence of a ‘genetic bottleneck’, so the long history of cross-breeding with ferrets may have obviated the expected reduction in genetic diversity.
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Main image: Polecats can breed with feral ferrets. © Chris Jolley/Getty