The pine marten (Martes martes) is an agile and playful hunter and in the Caledonian Forest is increasing in numbers again, because of an expansion of tree cover.

Global distribution

The pine marten has a Palearctic distribution: its geographic range extends from western Siberia across Russia and Europe to Scotland and Ireland, and from the northern limit of the boreal or coniferous forest in the north to the Mediterranean and the Caucasus region in the south. It is also found on many of the Mediterranean islands, including Sicily, Corsica, Sardinia and the Balearic Islands of Majorca and Minorca.

There are eight marten species in the world altogether, and these include the beech marten, which occurs in Europe and Asia, and the American marten and the fisher, both of which are found throughout northern parts of North America.

Distribution in Scotland

Until about 1800, the pine marten was widespread throughout Britain, but today it is confined mainly to remote, forested areas in the north and west of Scotland, with a few small isolated populations surviving in north Wales and northern England. Its range reached a minimum at the beginning of the 20th century, as a result of habitat loss through deforestation and conversion of the land to agriculture, hunting for its fur and persecution for predation on game birds and chickens.

Since then, its range in Scotland has increased due to the expansion of commercial forestry plantations, and more recently, the regeneration of native woodlands. The pine marten prefers well-wooded areas with plenty of cover, but it lives in more open habitats as well. There is a captive breeding programme underway in Kent, and suggestions have been made for the pine marten to be reintroduced to parts of southern England.

The pine marten is listed as a protected species in Appendix III of the 1979 Bern Convention on the Conservation of European Wildlife and Natural Habitats. It is also included in Annex V of the European Community's Habitat and Species Directive of 1992, as a species 'of Community interest whose taking in the wild and exploitation may be subject to management measures'.

In the UK, the pine marten is protected under the Wildlife and Countryside Act of 1981, and it cannot be trapped, disturbed or sold without a specific licence from the relevant government conservation agency – in Scotland this is Scottish Natural Heritage. However, despite this legal protection, martens are still killed inadvertently each year by traps or poisoned bait set out for crows or foxes.

Protected now from human persecution, and with its range in Scotland still expanding, the future of this agile but seldom seen predator of the Caledonian Forest looks secure.

The pine marten is a medium-sized member of the mustelid family of carnivorous mammals, whose other members include the stoat, weasel and badger. It is about the size of a cat, with a body up to 53 cm. long and a bushy tail which can be 25 cm. in length. An individual will weigh between 1.3 and 1.7 kg., with the female being slightly smaller than the male. In the wild, the pine marten can live up to 11 years, although the average lifespan is 3-4 years. In captivity ages up to 18 years have been recorded.

The body and tail are covered in dark brown fur, which is short and coarse in summer, but thicker and more silky in winter. The large cream-coloured throat patch or 'bib' distinguishes the pine marten from the beech marten, which has a white throat patch. The fur on the pine marten's paws is darker brown in colour, and the pads on the undersides of its feet are covered with fur in winter.

The pine marten has sensitive whiskers on its pointed muzzle and prominent, triangular ears. Its senses of hearing, sight and smell are all excellent, and it is both playful and curious in its behaviour. It is mainly active at night, and spends the day sleeping in a den, which can be a hollow in a tree, a disused squirrel drey, or a crevice amongst rocks. As a skilful predator, it has sharp canine teeth and claws, which are used to catch and hold prey. Martens are the only members of the mustelid family to have semi-retractable claws, and these give it considerable proficiency in climbing trees, while at the same time enabling it to run quickly on the ground.

Like other mustelids, the pine marten has anal scent glands, which are used (along with faeces, or scat) for marking territories and it also has an abdominal scent gland which is more active during the breeding season. Territories vary in size depending on the availability of food, with those of males ranging from 10-25 square kilometres and females from 5-15 square kilometres. Although it is a solitary animal, individual territories will often overlap and are not aggressively defended.

The pine marten is omnivorous, with small mammals forming the major part of its diet, particularly in winter. It feeds on voles (Microtus agrestis) and other rodents, birds such as the treecreeper (Certhia familiaris) and capercaillie chicks (Tetrao urogallus), insects, frogs and carrion . It is also one of the few predators able to catch red squirrels (Sciurus vulgaris), which it chases at speed through the treetops, using its claws and tail for agility and balance. However, in Scotland, pine martens do not eat significant numbers of squirrels, although they are a more important food source in other parts of their range.

In summer, the diet is more varied, and includes bird eggs, honey, caterpillars and fruits such as blaeberries (Vaccinium myrtillus). In a good berry season, these latter can form 30% of the marten's food and give a telltale blue colour to the animal's scat. Some food is stored in the summer and autumn for retrieval in the winter. As a mainly nocturnal animal, the pine marten forages at night or dusk, and can roam more than 10 kilometres from its den in search of food.

Because of the pine marten's elusive nature, its breeding behaviour is still inadequately known. Mating usually occurs when the animals reach two or three years of age, and takes place in the months of July and August, after a noisy and at times violent courtship in which the male chases the female at speed through the trees. However, the implantation of the fertilised eggs in the female's uterus is delayed for about seven months, and only takes place in February or early March.

After a gestation period of about a month, the young are born in late March or early April, in a nest which is an old squirrel's drey or bird's nest. The average litter size is three, and the young martens or kits weigh about 30 gm. and are blind at birth. After five weeks, the eyes open, and the mother, who is solely responsible for raising the young, weans them at about six weeks of age. At seven or eight weeks, the kits venture out of the den, and they can begin dispersing at 12-16 weeks, which is during the next breeding season, although some may remain in their mother's territory until the following spring.

As a predator, the pine marten plays an important role in regulating the numbers of its prey species. In the case of voles and other rodents which undergo periodic population explosions, it responds to the cycle of greater numbers by increasing the proportion of these animals in its diet. However, because of its delayed breeding cycle, any resultant increase in marten numbers does not occur until the following year, when food supplies may not be so abundant.

The pine marten has few natural enemies itself, apart from humanity. It is occasionally preyed upon by the golden eagle (Aquila chrysaetos), and the red fox (Vulpes vulpes) may kill a marten, not only to eat it, but also to eliminate a potential competitor for the same food resources.