In the past, pine martens (Martes martes) were one of Britain's most persecuted mammals.

They were wiped out in large parts of the UK by landowners and farmers anxious to prevent them from eating game and poultry.

At the start of the 20th century, they only survived in remnant populations in remote forests in northwest Scotland. In recent decades, however, pine martens have expanded their territory, and according to Government wildlife agency Scottish Natural Heritage they now number about 3000 adults across much of Scotland.

Martens were given full legal protection in 1988, so it is an offence to kill, injure or trap them, or to damage their shelters. The only exceptions are if they take up residence in the loft of home, or if a special licence is obtained from the Scottish Government.

Famously elusive, martens prefer woodlands, where they live in holes in trees, old squirrel dreys or birds' nests. Good climbers, they feed on small rodents, birds, eggs, insects and fruit. In the summer 30% of their diet can consist of blaeberries, turning their droppings blue.

They grow to 70 centimetres long, including a bushy tail, and are mostly chestnut-brown in colour, with a characteristic pale yellow bib on their chin and throat. They make shrill, cat-like calls in the mating season, have litters of three to five young in the spring, and live for about 10 years.