The Narrow-headed ant (Formica exsecta) is a rare wood ant entirely restricted to the Scottish Highlands and one remaining site in England. It is an important indicator of a healthy woodland ecosystem as it is associated with natural and man-made open glades and edges. It is also an important ‘functional species’, providing essential ecosystem services such as distributing the seeds of many plants and preying on range of invertebrates which feed on plants, such as aphids and caterpillars.
|Narrow-headed ant (Formica exsecta) © Gus Jones, Badenoch and Strathspey Conservation Group|
This ant has always had a highly disjunct distribution, but used to be more widespread in southern counties of England. The core population is now found in the ancient Caledonian Pine Forests of Speyside, with small outlying colonies in Deeside and Perthshire. It continues to hang on at its one remaining English site, a heathland SSSI in Devon, but it is feared this wonderful animal may soon become extinct in England.
The decline is thought to be the result of a combination of factors, including the dramatic loss of lowland heathland in England, disturbance through human activities (such as dirt-biking and pony grazing), and commercial forestry which destroys the natural habitat structure and is far too dense (and therefore dark) for the ants which depend on warm sunshine to raise the temperature of their brood. Fragmentation of woodland habitats in Scotland is also a serious concern as Narrow-headed ants are unable to cross areas of unsuitable habitat, and so can rarely colonise new habitat. This may result in inbreeding, as all of the colonies in one area are closely related and no queens are arriving from more distantly related populations. It also means that there are suitable areas that are unoccupied by the ants simply because they cannot cross the hostile habitat to get there!
The Narrow-headed ant is listed as endangered in the UK Red Data Book, and is both a UK BAP Priority Species and also listed on the Scottish Biodiversity List. Two important areas are receiving protection and conservation management – one as a Site of Special Scientific Interest (SSSI) and RSPB reserve, and the other a Forestry Commission Scotland forest where foresters are proactively helping to protect and enhance populations of the ant. The Scottish Wildlife Trust has also campaigned successfully for the better protection of this ant over the last decade and continues to provide management advice to those landowners with ants on their land. More information on the ecology of the species is available in a Scottish Natural Heritage commissioned report, and research is ongoing. To read this report, click here. It is hoped that conservation action, directed by improved understanding, will help ensure the Narrow-headed ant’s survival.
For more information on the Narrow-headed ant and other wood ant species click here to see the Forestry Commission’s Information Note on Forests and Wood Ants in Scotland.