A new university study has found that the population of these creatures, a genetic mutation of the North American grey squirrel that was responsible for the decimation of our native red variety across England, is rapidly expanding, and sightings are set to become more and more common.

The black squirrel has been forging its way into Bedfordshire from neighbouring Cambridgeshire and Hertfordshire, where it was first spotted nearly 100 years ago, and has set up camp in rural spots such as Whipsnade, Studham, Kensworth and Woburn.

The study will come as a welcome relief to nature lovers wondering if they have witnessed a trick of the light or a just a particularly dirty specimen. But less enthused about the growth in numbers will be the grey squirrels, who may be getting a taste of their own medicine from their more aggressive black cousins, which have higher levels of testosterone.

Dr Alison Thomas from Anglia Ruskin University, who carried out the study, said black mutations were not uncommon in the animal kingdom.

She said: "Many vertebrate species will occasionally produce black 'melanic' forms, including the leopard, tiger, jaguar, fox, rabbit and coral snake. The dense black colour results from an imbalance in the pigmentation process."

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