In the autumn 2024 issue (ARB Magazine 206, pages 60–66), Will Robertson described innovative work to create precision-carved homes for some of Europe’s most endangered tree-dwelling mammals. Here’s an update on results.
Garden dormice (Eliomys quercinus) showed a strong interest in minimally invasive precision-carved nest holes in our field study with Goedele Verbeylen and her team in Belgium – the first time that this has been observed with any veteranisation technique. Dormice of different ages visited one carved nest hole 16 times. In the same family as the UK’s hazel dormice, garden dormice are identified as Vulnerable on the IUCN Red List. Goedele said, ‘The garden dormice quickly discovered some of the carved hollows, and I can’t wait until hibernation is over to see if they will start building nests in them.’
Enormous improvements in the speed and precision of freehand minimally invasive chainsaw carving techniques were achieved in a study organised with Dario Wegmüller and his team at Forst-Seelan in Switzerland. Creating nest holes for dormice entirely through a narrow and precisely carved entrance with no damage to surrounding cambium in under 40 minutes became possible for the first time.
A garden dormouse emerging from a carved nest hole.
Great spotted woodpeckers have been observed working to enlarge a carved nest hole.
Red squirrel.
Will Robertson working on a precision-carved nest hole.
Carving rectangular, rather than round, entrances with carefully planned dimensions – for hazel dormice (Muscardinus avellanarius), 16 x c. 40mm – allows dormice to enter but helps keep birds out. Damage to the cambium of living trees is restricted to only the entrance hole, so it is hoped that these nest holes will be available for many generations of dormice to come. Field studies will help gather information on how trees react over the long term.
Pat Morris, whose research has laid the basis for our understanding of dormice in the UK, said, ‘This technique looks very promising! Carving nest holes through a narrow entrance gives minimal visibility to predators and stable temperature and humidity. These nest holes should be particularly valuable for anywhere that there is food but few holes (e.g. coppice with standards and mature forest, which are otherwise potentially good Muscardinus habitat).’
Another wildfire severely affected Roach’s mouse-tailed dormice (Myomimus roachi) in southern Bulgaria, so our focus there has changed to doing what we can to help save them from the brink of extinction in Europe.
Endoscopy of chainsaw-carved bat roosts at Glengarriff Nature Reserve in Ireland showed internal dimensions matching specifications and strong occupancy by the Bern Convention-listed Kerry slug (Geomalacus maculosus).
In studies by Susan Kerwin at Bat Rehabilitation Ireland and by the team at Stiftung Wildstation Landshut in Switzerland, a wide range of European bat species in rehabilitation showed a strong preference for precision chainsaw carved roosts over other roosting opportunities.
Susan said, ‘Having the opportunity to work with Will on this project has been fascinating and has really given us an insight into the roosting preferences of the bats in our care. With often more than one species of bat occupying the bat flight at any time, we have had the opportunity to record interspecies relationships within the roosts. This allows the bats to exhibit as natural behaviour as possible. By providing the bats with several options of precision-carved roosts as well as the option of bat boxes, we are seeing a definite overall preference for the natural option in all species.’
For more information about techniques and latest news on the project, visit www.new-homes-for-old-friends.cairnwater.com
Separately, Jim Mullholland and team have demonstrated use of more established veteranisation techniques by Bechstein’s and Barbastelle bats for the first time.
Images of visitors to nest holes courtesy of Goedele Verbeylen.
Will Robertson is a climbing arborist who passionately promotes the opportunities that practice and research in arboriculture offer. As a proudly gay/bi guy, he’s committed to making our industry inclusive and welcoming. Contact him at w.robertson@cairnwater.com
This article was taken from Issue 208 Spring 2025 of the ARB Magazine, which is available to view free to members by simply logging in to the website and viewing your profile area.