The October meeting of the Dumfriesshire and Galloway Natural History and Antiquarian Society (D&G Heritage) took place via Zoom only, as the lecture room was unavailable for an in person meeting.
The speaker was Johnny Birks, assisted by John Martin, and their talk was entitled Twenty years of studying Pine Martens in Galloway Forest Park.
The pair have previously worked for Nature England and the Environment Agency respectively.
The pine marten is the largest British representative of the mustelid (weasel) family, and is an aggressive omnivore, feeding primarily on small mammals. It lives in forests and breeds in cavities in trees, but being mainly nocturnal is rarely seen.
It had until recently suffered from severe persecution by humans, being killed for its fur or for sport. Prior to this it was probably the second commonest carnivore in Britain, with an estimated population of around 150,000, but by 1915 it had become the second rarest (after the wild cat), and confined largely to the northwest Scottish Highlands, with smaller populations in the Lake District and Snowdonia.
It had become extinct in Galloway by the mid 1800s, but reintroduction was started in the early 1980s, however, it breeds slowly, so recovery of the population would take time, and it was to aid this that the speakers had embarked on a programme of providing artificial breeding sites using specially-designed boxes, or dens.
Part of the problem is that pine martens now use mainly commercial forestry plantations, rather than mature broadleaf woodlands. The old gnarled trees of the latter can provide natural dens, a process aided on the Continent by the presence of the large black woodpecker, whose nesting holes can subsequently be accessed by pine martens, but the black woodpecker does not occur in Britain. In contrast forestry plantations, while generally undisturbed, are harvested when the trees are still relatively young and cannot provide natural dens.
The first boxes to be used had two entrance holes with a protected area in between for the breeding female. However, while successful in attracting breeding pine martens they were heavy, and could only be placed in large conifers that were likely to be felled shortly. More recently a modified box using lightweight plastic for the sides and roof has been trialled in the Fleet Valley basin. Although these also attracted the pine martens, with all of them having been used within four years, it was found that they were only used as winter shelters, not for breeding. However a further modification to increase the depth of the plastic chamber enabled them to be used for breeding, and during the study period (2014-2017) the estimated number of pine martens in the Fleet Valley basin increased from about 17 to about 30. Despite that fact that it was not possible to study a control group of animals in an area without boxes, it was thought unlikely that any other external factors could have caused the increase.
Monitoring pine martens without disturbing the animals by looking into the boxes was problematic. The most successful method was found to be by studying their faeces, or ‘scats’ in the woodland. These had to be genetically analysed to ensure that faeces of other animals such as foxes were not included, but while expensive this also allowed individual animals to be identified by their genotype, thus aiding population estimates. Recently thermal imaging has also been used as a means of detecting occupied boxes.
Some interesting points arose during questions to the two speakers at the end of the meeting. The popular notion that pine martens aid the survival of red squirrels by selectively predating greys was discussed, and this does seem to be the case where there is a well-established pine marten population, though they will take reds if they can. The latter, being a native species that has evolved with pine martens present, has developed strategies for avoiding capture, whereas the grey squirrel was introduced relatively recently to Britain from north America, where there are no pine martens, and so they have not evolved with a strategy to avoid predation. It was also suggested that the introduction of pine martens caused increased predation of ground-nesting birds, but Johnny Birks said that he had not found this to be the case.
The next meeting will be on Friday, November 8 at 7.30pm in The Bridge, Glasgow Road, Dumfries, and will also be streamed on-line via Zoom. The speaker will be the surveyor Bruce Keith, who will talk about Scotland beneath the Surface. Visitors welcome to attend.
Further information from www.dgnhas.org.uk or on Facebook.