Grey Squirrels in Young Woodlands
The damage that grey squirrels can do to young trees has been widely documented and the different methods of control (principally shooting and trapping) have also been discussed. My observations in a small mixed woodland point to a silvicultural solution to the problems of squirrel damage to young trees.
Nursery Wood was planted in 2008 with a wide variety of broadleaved trees with the object of creating a fully functioning woodland ecosystem. The particular part of the wood under discussion was planted with a band of mixed native shrubs on the edge. Inside the wood the main trees are pedunculate and sessile oak, ash, field maple and hazel with smaller amounts of alder, wild cherry and other species, all planted as an intimate mixture.
In spring 2016 I noticed grey squirrels in a corner of the wood for the first time and shortly afterwards I noticed the first signs of bark stripping on some of the field maples. I was concerned that the squirrels would damage the oaks, my principal timber tree in this area, but I was unsuccessful in trapping or shooting any of them.
By the end of the summer virtually all the field maple in an area of about 0.2 hectares had been severely damaged but not a single tree of any other species had been touched. The field maple had been planted as an understorey species to keep the trunks of the taller timber species in the shade, so I was not concerned about the bark stripping, in fact it was helping to stop the field maple from competing with the timber trees in the canopy.
Had the presence of field maple, which is very susceptible to bark stripping, stopped the squirrels from attacking the oak trees? I will be watching this closely over the next few years to see if this pattern of preferential bark stripping is repeated.
An internet search has revealed that the Forestry Commission states that “the planting of “sacrificial” species in mixtures has not been shown to reduce damage to “high risk” species” www.forestry.gov.uk/pdf/fcpn004.pdf/%24FILE/fcpn004.pdf . There is no reference to any studies which back up this rather sweeping statement.
It is no help to woodland owners with squirrel problems in their existing woods, but all future woodland planting should have an intimate mixture of “sacrificial” species. There need be no loss of oak timber production from such mixed woods. The finest French oak woods have an understorey of hornbeam to keep the oak stems clean. Field maple could play the same role in Britain and keep squirrels away from the oaks as well.