Threats

Changes in woodland management, deforestation, inappropriate afforestation, urban expansion, human disturbance and agriculture are all linked to the loss of suitable habitat for woodland ants.

Across Europe, wood ants are under threat and for some species; their range seems to be shrinking. A number of studies have shown that forest fragmentation and human disturbance all have negative impacts on wood ants and appropriate management is essential if populations are to persist and expand.

Some species have become extinct from some parts of their former range, for example Formica rufibarbishas disappeared from heathland in the south of England and Formica rufa has vanished from some parts of northern England, north Wales and the Midlands. Formica pratensis is now completely extinct from mainland Britain, now only existing on the Channel Islands.

In terms of the wood ants (Formica rufa, Formica aquilonia and Formica lugubris) maintaining sunny glades and rides is important, particularly on south-facing slopes, in order to provide the high levels of insolation the ants need. Wood ants are relatively adaptable however and nests will also encroach onto heathland and scrub adjacent to the woodland if there is sufficient food available.

Studies in Finland indicate that the main factors in determining distribution of wood ants is the availability of suitable nest sites, a favourable microclimate, and a good food supply. Sap-feeding bugs are especially important, both as prey and for the honey-dew that they produce. It has been estimated that 90% of foraging activity by the ants is in the canopy of trees near the nest.

Luckily for these ants, in the UK many of the sites where they exists are designated as Sites of Special Scientific Interest, National Nature Reserves or are managed by the RSPB, National Trust, National Trust for Scotland, local Wildlife Trusts or the Forestry Commission, which manage sympathetically for woodland species.

Status

In the UK, both Formica rufibarbis and F. exsecta are UKBAP Priority Species and are considered endangered, having extremely isolated and fragile colonies. Formicoxenus nitidulus is also a UKBAP species. Although almost definitely under-recorded, it is entirely dependent on wood ants for its survival. Formica sanguinea is notably scarce, although an abundance of recent records across north east Scotland suggest it may simply be under-recorded. Even for those species considered locally common and widespread - Formica rufa, Formica aquilonia and Formica lugubris - we still do not fully understand the status and distribution of colonies and many nests are not recorded in national databases.

Formica exsecta

This species is directly affected by habitat loss and inappropriate management, and indirectly by competition from wood ants. Its inability to disperse over long distances (queens are believed to disperse on foot) make isolated nests and colonies even more vulnerable. Because of the sun-loving nature of this species, it is crucial that open glades are maintained around nests and corridors of open habitat exist to enable colonies to expand and relocate if necessary, and to allow new queens to disperse. Historically, grazing by large herbivores and natural disturbance such as fire would have created and maintained mosaics of different vegetation heights and in some places would prevent the growth of seedlings. Today, the targets for woodland expansion threaten the open habitat required by F. exsecta. As canopy cover increases wood ants will colonise and displace F. exsecta. If no suitable habitat is available close by colonies will die out.

Formica sanguinea

Recent evidence suggests this species is much more common than previously thought. Certainly across north east Scotland, it is able to take advantage of newly felled areas within commercial plantations. Not only do these areas provide suitable nesting sites, but there is also an abundance of Formica lemani which this species enslaves. Continued monitoring at key sites will help to ensure forest management is sympathetic to this species. 

Formica rufibarbis

The reasons for the red-barbed ant’s decline in the UK include loss of suitable heathland habitat through human development, inbreeding and disturbance. With only three nests at Chobham Common, the only mainland site for this species, this ant is under threat of extinction on mainland Britain. Recent observations suggest that the nests in Surrey are all one sex (no males being produced), making it only a matter of time before the population becomes unviable and dies out.

A reintroduction programme was started in 2008 lead by the Zoological Society of London and Surrey Wildlife Trust and finding by The Heritage Lottery Fund. The aim of this project was to establish a healthy, self sufficient population in Surrey. A trial release took place on St Martin’s in order to establish release protocol followed by a release at Chobham Common. Each colony released consisted of a queen, ten workers plus pupae and larvae.

Following release, a protocol was established to monitor the progress of released colonies which involved using bait close to release sites to assess ant activity.

Surrey Wildlife Trust have been creating suitable habitat for these ants on lowland heath to act is potential release sites. Creation of bare ground as nesting habitat for F. rufibarbis will also benefit a range of other UKBAP heathland species including heath tiger beetle (Cicindela sylvatica) and the mottled bee-fly. Proposed heathland management for F. rufibarbis involves creating bare ground, controlling succession to avoid excessive scrub and bracken encroachment, monitoring disturbance (trampling) and potential grazing and burning regimes. 

The long-tern goal for the reintroduction project is to release 40 captive-reared nests into the wild each year in order to create self-sustaining populations at Chobham Common National Nature Reserve, Wentworth Nature Reserve, Lightwater Country Park and Sunningdale Golf Course. In the future it is hoped that mated queens may be sourced from Europe in order to supplement the British gene pool.