Apr 25 2022

“Anthill Mob” protecting hairy climate heroes at Ledmore and Migdale

A group of Woodland Trust volunteers nicknamed “The Anthill Mob” have rushed to the rescue of hairy climate heroes under threat from an invasive non-native plant.

Hairy wood ants boost the carbon absorption of woodland, but risk being overwhelmed by Gaultheria shallon, a garden plant that has gone wild to become a serious pest in lowland woodland around the UK.

Site manager Ross Watson set volunteers Chris and Meg Mellish the task of surveying for the nests of hairy wood ants over the winter at Ledmore and Migdale, in order that they can be avoided and protected during any future work at the site. The Sutherland wood is at the most northerly edge of the ants’ range. Over 50 anthills were found, but the survey also revealed an immediate threat to the insects.


Meg and Chris Mellish who surveyed for nests

Some of these newly discovered nests were surrounded by an invasive garden plant, Gaultheria shallon that is also threatening parts of the oakwood. The ants prefer sunny open glades that are south facing and so does the plant. If left unchecked, it forms dense thickets that exclude native vegetation. It would overwhelm our ant nests too if we let it.


Anthill with invasive plant visible around the edge.

Chris and Meg were joined by more helpers to become a Gaultheria clearance squad aka The Anthill Mob. This Spring they have been manually removing the plant from around the anthills.


Ross Watson, Chris Mellish, Anna Currall and Meg Mellish – The Anthill Mob! Pic by Cherry Alexander/ArcticPhoto.

A common garden plant, it spreads to the wild when birds eat its berries passing the seeds out in their droppings. Once one plant is established it spreads via underground stems.

The hairy wood ant (Formica lugubris) collects large quantities of honeydew from sap sucking aphids in trees. This honeydew is a major source of carbohydrate for the adult workers and represents a significant input of carbon into soils in forests where they live.

A close relative of the hairy wood ant has been shown to account for up to 39kg of carbon per hectare per year.

Aside from their carbon capturing role, wood ants are a keystone species affecting many other organisms. They remove insect pest species from trees and provide food for other animals including capercaillie and badgers.

Wood ants eat a variety of other insects including caterpillars and beetles, but the bulk of their diet is made up of honeydew they “milk” from aphids. In return the ants protect the aphids from predators. Wood ants are commonly seen moving up the trunks of pine trees to collect honeydew from pine aphids living high in the canopy.

This is a great example of how biodiverse ancient woodlands can capture and store more carbon. It also shows the vital role our volunteers play. Without the time and care from Chris, Meg and the others these nests may well have been lost.


Hairy Wood Ants. Pic by Cherry Alexander/ArcticPhoto

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