Re-introduction of the Southern Damselfly to Venn Ottery Common, Devon, UK

Summary

The southern damselfly (Coenagrion mercuriale), protected under multiple European conventions and the only Odonata species in the UK's first Biodiversity Action Plan, had declined over 30% in UK site numbers since 1960 and was lost from Venn Ottery Common, a Devon Wildlife Trust reserve, in 1989 due to disruptive ditch digging and reduced grazing that let invasive tussock grass smother its breeding runnels. A multi-agency steering group selected Venn Ottery for the UK's first southern damselfly reintroduction, given recent extinction, acceptable water chemistry, strong landowner commitment, and potential to create a gene-flow-connected meta-population with two nearby populations. Beaulieu Heath in the New Forest, identified through genetic surveys as the UK's most diverse and dense population, was chosen as donor site; a pilot transfer of 57 adults in June 2007 proceeded despite an unexpected water-level drop, followed by two years of habitat restoration removing birch trees, introducing grazing cattle, and installing eleven dams to slow a previously unsuitable stream. By 2009, conditions had improved enough, and breeding descendants from the 2007 pilot were already found on site, to proceed with a larger transfer of 400 females and 100 males moved over six batches across ten days, with only three individuals lost in transit; most began reproductive behavior within minutes of release. Major difficulties included securing a reliable, slow year-round water supply and maintaining grazing to prevent vegetation encroachment. The project rates itself Partially Successful, still at an intermediate stage but expected to become fully successful pending confirmed breeding and gene flow with neighboring populations.