Music by Pine Marten the band. Song: Doggone from the EP ‘Gone Beyond’.
The pine marten is a medium-sized animal, about the size of a domestic cat, with a slender and elongated body, and a long bushy tail. It has prominent rounded ears that have a pale outline, and its fur is chestnut to dark brown in colour. Pine martens have a distinctive creamy-yellow bib on the throat that extends to the chest, and helps to tell it apart from the American mink and feral ferret. Mink fur is dark chocolate brown or black in colour with no throat or chest markings, although there is usually a white chin patch. Feral ferrets have white faces with a characteristic facial mask, which can be quite variable.
Habitat and range
Pine martens like woodland, preferably large-scale deciduous woodland, but they will also live in small pockets of deciduous woodland and are found in commercially managed coniferous plantations. They can also live in scrub, rocky areas and crags; in fact, any place that provides shelter and food. Pine martens prefer to rest and breed above ground, usually in tree cavities, but where these are not available they will use a variety of sites such as rock crevices, burrows, buildings, nests, squirrel dreys and log piles.
The pine marten is a territorial animal. The size of its territory can range from 50-400 hectares, with some overlap between neighbouring individuals (one hectare is approximately the size of an international rugby pitch).
Distribution and population
The pine marten is currently found throughout the island of Ireland and is present in every county, but is less common in Mid-Ulster and parts of the south, particularly Limerick and Cork. The pine marten almost became extinct in Ireland during the 20th century, but its population has recovered due to legal protection, restrictions on the use of poisons and the increase in coniferous plantations. The most recent estimate of the pine marten population size in the Republic of Ireland, based on a survey conducted in woodlands, suggests a population of approximately 4,000 animals.
Although a carnivore, the pine marten has a varied diet and eats both animal and plant material, including small mammals, birds, eggs, amphibians, invertebrates, berries, fruits, fungi and carrion. The pine marten will eat what is plentiful locally, including food left out for pets and birds. It will also take food from rubbish bins.
Pine martens are solitary animals and adult animals avoid contact with each other throughout most of the year. They are active during the daylight hours of spring and summer, when they breed. In autumn and winter they are mostly active at night, and in winter they spend most of their time in resting and den sites. The pine marten is extremely agile and a very confident climber.
Pine martens mate once a year in July and August, but the young (called kits) are not born until the following March or April. Pine martens experience ‘delayed implantation’, whereby eggs that are fertilised following mating in the summer remain in stasis through the winter. In January, if conditions are favourable and the female is in adequate condition to carry a pregnancy, the fertilised eggs implant in the uterine wall and are able to develop.
This ensures the kits are born when food is plentiful during the summer months. Females can give birth to up to five kits, though the average is two to three. The kits are entirely dependent on their mother and do not leave the natal den for the first six weeks. By mid-summer they are semi-independent, and by autumn they are fully grown. They remain with their mother for up to eighteen months, when they are forced to disperse and set up their own territories. Only a small number of kits will survive to become adults and breed. Juvenile females are sexually mature at one year old, whereas males do not reach sexual maturity until three years of age.
A pine marten can live for up to 12 years, although the majority of individuals do not live more than five to eight years. Pine martens are killed by foxes and eagles, but they face a range of other challenges for survival, including habitat fragmentation, being killed while crossing roads, and persecution.
Interactions with squirrels
Research by Emma Sheehy and Colin Lawton of NUI Galway suggests that the recovery of the pine marten population in certain parts of Ireland has caused a significant decline in the number of non-native grey squirrels. This has allowed the native red squirrel to return to woodlands from which it had been driven out by the grey squirrel. The grey squirrel was introduced to Ireland in the early 20th century and soon displaced the red squirrel, through a combination of competition for food and disease. Adult grey squirrels are twice the size of red squirrels and, although they have a very similar life cycle and biology to the red squirrel, have a broader diet.
The squirrel/pine marten relationship was explored more rigorously in Scotland by Emma Sheehy and a team from the University of Aberdeen. They found that grey squirrel occupancy decreased with increased abundance of pine martens, whereas red squirrel occupancy was positively related to pine marten abundance. The findings suggest that red squirrels can coexist with pine martens but grey squirrels cannot, though grey squirrels still occurred in areas where there was low pine marten density (newly colonised areas).
What is not yet understood is the mechanism underpinning grey squirrel decline in the presence of pine martens; whether it is direct predation, increased stress from exposure to pine martens (pine martens creating a ‘landscape of fear’), or a combination of factors. Pine martens and red squirrels, however, have coevolved over tens of thousands of years, and though red squirrels are occasionally predated by pine martens, they coexist throughout their range in Ireland, the UK and Eurasia.