Bringing Back Bele: The Pine Marten Recovery Project in Wales

In this article, Dr. Jenny MacPherson (Pine Marten Project Manager, The Vincent Wildlife Trust), tells more about the pine marten recovery project in Wales…

The pine marten, known in Welsh as Bele or Bele’r coed (marten of the wood), is now back in Wales in healthy numbers. Between autumn 2015 and 2017, a total of 51 pine martens have been translocated from the Highlands of Scotland to the forests of the Cambrian Mountains, in an effort to prevent the species from going extinct in Wales. This has been carried out as part of The Vincent Wildlife Trust (VWT)’s Pine Marten Recovery Project.

The Pine Marten
The pine marten (Martes martes), is one of six members of the weasel family (mustelidae) native to the UK. Pine martens are about the size of a domestic cat, with males being slightly larger than females. In common with many carnivores, pine martens are solitary and territorial and, while a male home range usually encompasses that of one or two females, there is rarely overlap between adult male territories. They are attractive animals with light to chestnut brown fur and a distinctive creamy yellow to apricot throat patch or ‘bib’, the shape of which is unique to each individual. Pine martens are predominantly associated with wooded habitats and are adept tree climbers. Their many adaptations for arboreal life include powerful forelimbs, a long tail to aid in balancing, and sharp, semi-retractable claws.

Fall and Rise
Despite once being common throughout Britain, the pine marten had declined, along with its woodland habitat, over a long period of time. This was exacerbated by the intensive predator control that became widespread throughout the 19th century so that, by the early 20th century, the main pine marten population was confined to northwest Scotland and only a few isolated animals remained in the remote uplands of northern England and Wales.

With increases in afforestation and legal protection, the pine marten population in Scotland has been recovering well and expanding since the 1980s, but this is not the case elsewhere in Britain. There have been sightings, occasionally verified by photographic or DNA evidence, of individual animals in some areas, but, after 30 years of research and surveys, the VWT had found no evidence of pine marten recovery in England and Wales. While it is likely that pine martens will naturally recolonise parts of northern England as the population in Scotland continues to expand southwards, the urbanised areas in north-west and central England may act as a barrier to dispersal further south. This led to the conclusion that intervention was necessary to prevent complete extinction of the pine marten south of the Scottish border and to restore viable populations of martens to their historical range in southern Britain (Jordan, 2011).

The Pine Marten Recovery Project
The VWT’s pine marten recovery project began in 2014, starting with a study to examine the feasibility of using translocations as part of the conservation strategy for this species (MacPherson, 2014). IUCN guidelines for conservation translocations were closely adhered to throughout the process. Habitat suitability and population viability models were used to classify regions according to their potential to support a viable breeding population. Pine martens are not restricted to forests, but each animal requires a significant amount of woodland within its territory (around 200 hectares). Central Wales was identified as having high biological suitability because of the large amount of well-connected, suitable woodland habitat and relatively low risk to pine martens of road mortality. There was also recent DNA evidence (in 2007 and 2012) that indicated there could still be extremely small numbers of pine martens still present.

Evaluating the social feasibility of translocating pine martens to Wales was as important as the biological feasibility. The results of a wide-scale public opinion survey suggested that the majority of people would be in favour of action to prevent the pine marten from becoming extinct in Wales. However, crucially, much more detailed consultations with stakeholders and communities in the prospective release areas were carried out in order to answer questions, discuss specific issues, and ensure that there was local involvement and support for the project. All the feedback gathered during community discussions and stakeholder consultations in the early stages, was taken into account when making the final decision to proceed, and in deciding where releases should take place.

GIS data were used for the initial habitat suitability assessments and these needed to be ground-truthed. Field surveys were carried out to appraise the structural and species diversity of woodlands, and the extent of ground cover and potential denning sites in the proposed release area. Survey data were also used to assess the availability of prey and other food. The pine marten is a generalist predator and in Britain its diet includes small mammals, but fruit, including bilberry, is also important, as are birds, invertebrates and carrion. Therefore, it was necessary to be sure that there were enough resources available in the release area to support sufficient numbers of pine martens for a viable population.

Alongside all of this work, we also needed to find a suitable source of animals for translocation and release. Field surveys were carried out to identify a number of sites and source populations, where two to four individuals could be taken at the end of the breeding season without having an impact on population viability. This was based on site-specific marten density estimates and harvesting models. Following the preparation work, including disease risk analysis, and with licences and permissions from Scottish Natural Heritage and Forestry Commission Scotland and Natural Resources Wales (landowners of the source and release sites), trapping and translocations began. A total of 20 healthy adult pine martens were translocated in autumn 2015, with another 19 the following year and the final 12 in 2017. These have been taken from robust populations spread right across the north of Scotland.

Research and Monitoring
Research and monitoring are key to improving both the science and practice of conservation translocations. All the pine martens are radio-collared and studied intensively for at least a year following release. Some of the research is focused on the martens’ ranging behaviour and habitat use in the days and months following release. All translocations are essentially exercises in forced dispersal, but dispersing animals in many, even relatively asocial species, relies on the presence of conspecifics to assess habitat suitability. Translocated individuals invariably face an environment with no, or very few, conspecifics, therefore they may not settle in suitable habitat at the release site, choosing instead to disperse to another area in search of conspecifics. Radio-tracking results show that the first animals released in 2015, into “empty” habitat, initially made some relatively long distance exploratory movements, often using wooded river valleys to travel around, before tracking back to the release area. It took approximately four months before they established stable home ranges. However, those released in the second year, when there were conspecifics present, settled much more quickly and established territories within about two months of being released.

Pine martens have relatively large territories for their size and so they are not central place foragers and need a number of different den and lie-up sites within their home range. They preferentially den above ground in tree cavities, birds’ nests and squirrel dreys, but they will also use cairns, tree roots and brash piles. Tree holes are particularly important to female martens for breeding dens, so they can safely rear their kits above ground away from predators such as foxes. Extensive mature conifer plantations provide martens with plenty of cover, and previous radio-tracking studies have shown that they spend much of their time in such areas. However, while they may be used by pine martens as habitat and for feeding, even-aged plantations may not provide good denning opportunities, generally due to the lack of deadwood habitat and cavity trees. To counteract this, a network of artificial den boxes was put up throughout the release area, and we have observed some of the translocated animals using them. However, our radio tracked pine martens have also found many natural den sites that we may have overlooked, including tree holes, squirrel dreys, rocky ledges and derelict buildings.

Breeding Success
Trapping in Scotland was carried out immediately after the marten mating season, to maximise the chances of translocating females that had already been mated. Pine martens, in common with some of the other mustelids, have delayed implantation so, although mating takes place in July-August, the females do not become pregnant until early the following year. If females are under stress at this time or if there is a shortage of resources, any fertilised eggs do not implant and develop into pregnancy.

The timing of releases has been shown to have an impact on reproductive success in other mustelids (Facka, 2016). It has been suggested that females released in autumn should have an advantage compared to females released in late winter and spring because they will be better acquainted with, and able to exploit, resources in the new landscape when reproduction re-activates. Pine martens were released between September and the beginning of November in 2015. By early April, following the first release, some of the radio tracked females began staying very close to a chosen den site, which suggested that they might have had kits, but we had to wait until the middle of May to find out for certain. By this time the kits are quite well developed and the females start to leave the den for longer periods of time so we were able, under licence, to check the dens. Happily, this confirmed that at least four of our females successfully bred in 2016 and we counted five healthy looking, Welsh-born pine marten kits.

In 2016, all 19 martens were released between September and early October. From March onwards, radio tracking of the females was intensified to determine if any of them were showing signs of breeding. Camera traps were also used at den sites, along with a combination of other evidence. This confirmed that at least five females bred in spring 2017, with breeding by a further two females suspected but not confirmed. This has resulted in at least 10 Welsh-born pine marten kits this year, four of which were born to ‘PM16’ who was released in autumn 2015. This means that there was at least one male in her territory with which she mated in Wales last summer.

Wider Benefits
The return of a healthy pine marten population has the potential to provide benefits beyond biodiversity. The interaction between pine martens and grey squirrels has been a subject of great interest since distributional evidence from a study in Ireland, showed declines in grey squirrel numbers as the pine marten recovered in some areas. It is not yet known if a similar effect will be observed in Britain, but further research is ongoing. There is also the prospect of pine martens benefitting local businesses through ecotourism, as is the case in Scotland.

Engagement with communities in the project area is ongoing. Many local volunteers are directly involved in the project by radio tracking the martens and now use more non-invasive monitoring methods such as camera, scat and hair tube surveys. Ultimately, this local support and ownership will be as important to the long-term integration of pine martens back into the Welsh landscape, as is all the science and preparation that have led to the return of the pine marten to Wales.

About the Author: Dr. Jenny MacPherson is the pine marten project manager at the Vincent Wildlife Trust. She has been involved with species reintroduction programmes in the UK and in Tanzania and carried out research on the ecology and behaviour of a range of mammal species including pine marten, dormice, red squirrel, hedgehog, water vole and mink.