Pine Marten

A Tree-Climbing Acrobat

The European pine marten (Martes martes) is a lean member of the weasel family, about the size of a domestic cat, usually wearing dark brown fur with a cream-yellow throat patch, or bib, that is unique to every individual, much like a human fingerprint. Females measure 46 to 54 centimetres long, not counting the tail, and weigh around 1.5 kilograms; males run larger, at 51 to 54 centimetres and about 2 kilograms.

Its climbing gear is the real trick. Sharp, semi-retractable claws and ankles that rotate through 180 degrees let it climb up and down trees, and muscular legs and long feet help it leap from branch to branch. In the wild, a pine marten is only likely to reach seven to ten years.

A Diet That Barely Touches Squirrels

Pine martens are adaptable opportunists. Meat makes up 30 to 70 percent of the diet, and the rest is fruit, nuts, eggs, invertebrates and fungi, changing with the season and whatever is locally abundant; voles are a particularly important prey item in Britain. Oddly, studies in Britain and Ireland find red squirrel rarely in a marten’s diet, yet in Ireland and Scotland, where martens are recovering, grey squirrels are decreasing and red squirrels are moving back into the woods.

A Squirrel Regime Change A survey of the Irish midlands found the invasive American grey squirrel population had crashed across roughly 9,000 square kilometres of its former range, and native red squirrels were common again after an absence of up to 30 years. The authors suggest pine marten abundance may be a critical factor, but scientists are still not sure why or how this happens.

Delayed Motherhood

Pine martens are considered slow breeders: they wait until they are two or three years old to start, and breed only once a year, mating in midsummer. What follows is delayed implantation, where fertilised eggs sit in the womb without attaching for around 230 days, a strategy that ensures kits are born in early spring, as the weather warms and food becomes more abundant. Kits are born blind and weigh about 30 grams; a litter is usually one to three, but up to four or, rarely, five when food has been particularly abundant, and the young stay in the den, totally dependent on their mother, for about six or seven weeks.

Back From the Brink

Pine martens are thought to have been Mesolithic Britain’s second most common carnivore, but woodland clearance and predator control devastated them; by 1915 they were confined to just a few remote areas of Britain and Ireland and had become the second rarest carnivore there. Full legal protection came in 1988. Between 2015 and 2017 the Vincent Wildlife Trust moved martens from Scotland to mid-Wales, and later projects reintroduced them to the Forest of Dean and Devon. The global IUCN assessment lists the species as Least Concern, but the Red List for Britain’s mammals rates it Critically Endangered in England and Wales and Least Concern in Scotland.