European pine marten

Pine marten at the British Wildlife Centre

In Great Britain, the species was for many years common only in northwestern Scotland.[5] A study in 2012 found that martens have spread from their Scottish Highlands stronghold, north into Sutherland and Caithness and southeastwards from the Great Glen into Moray, Aberdeenshire, Perthshire, Tayside, and Stirlingshire, with some in the Central Belt, on the Kintyre and Cowal peninsulas and on Skye and Mull. The expansion in the Galloway Forest has been limited compared with that in the core marten range. Martens were reintroduced to the Glen Trool Forest in the early 1980s and only restricted spread has occurred from there.[6] This may be due to ongoing persecution and trapping by local gamekeepers.

In England, pine martens were long considered to be extinct. Analysis of a scat found at Kidland Forest in Northumberland in June 2010 may represent either a recolonisation from Scotland, or a relict population that has escaped notice previously.[7] There have been numerous reported sightings of pine martens in Cumbria, however, it was not until 2011 that concrete proof—some scat that was DNA-tested—was found,[8] followed in October 2022 by images being captured of a pine marten in Grizedale Forest.[9] In July 2015, the first confirmed sighting of a pine marten in England for over a century was recorded by an amateur photographer in woodland in Shropshire.[10] Sightings have continued in this area, and juveniles were recorded in 2019, indicating a breeding population.[11] In July 2017, footage of a live pine marten was captured by a camera trap in the North York Moors in Yorkshire.[12][13] In March 2018 the first ever footage of a pine marten in Northumberland was captured by the Back from the Brink pine marten project.[14] In September 2022, the first pine marten to be seen in London in a century was spotted by the Zoological Society of London's wildlife cameras as part of a hedgehog monitoring program.[15]

There is a small population of pine martens in Wales. Scat found in Cwm Rheidol forest in 2007 was confirmed by DNA testing to be from a pine marten. A male was found in 2012 as road kill near Newtown, Powys. This was the first confirmation in Wales of the species, living or dead, since 1971.[16] The Vincent Wildlife Trust (VWT) has begun a reinforcement of these mammals in the mid-Wales area. During autumn 2015, 20 pine martens were captured in Scotland, in areas where a healthy pine marten population occurs, under licence from Scottish Natural Heritage. These animals were translocated and released in an area of mid-Wales. All of the martens were fitted with radio collars and are being tracked daily to monitor their movements and find out where they have set up territories. During autumn 2016, the VWT planned to capture and release another 20 pine martens in the hope of creating a self-sustaining population.[17]

The marten is still quite rare in Ireland, but the population is recovering and spreading; its traditional strongholds are in the west and south, especially the Burren and Killarney National Park, but the population in the Midlands has significantly increased in recent years.[18] A study managed by academics at Queen's University Belfast, using cameras and citizen scientists, published in 2015, showed that pine martens were distributed across all counties of Northern Ireland.[19]

The European pine marten has lived to 18 years in captivity, but the maximum age recorded in the wild is only 11 years, with 3–4 years being more typical. They reach sexual maturity at 2–3 years of age. Copulation usually occurs on the ground and can last more than 1 hour.[22] Mating occurs in July and August but the fertilized egg does not enter the uterus for about 7 months. The young are usually born in late March or early April after a month-long gestation period that happens after the implantation of the fertilized egg, in litters of one to five.[4] Young European pine martens weigh around 30 grams (1.1 oz) at birth. The young begin to emerge from their dens around 7–8 weeks after birth and are able to disperse from the den around 12–16 weeks after their birth.