Efforts in the wild

The longhorn beetle (Plagionotus detritus) is critically endangered. It was once found in a number of landscapes in southern and central Sweden, but today remains only in Stockholm county. The county administrative board has therefore been asked by the Swedish Environmental Protection Agency to co-ordinate work on a national action plan.

The existing action plan, which was originally scheduled to run from 2005 to 2011, was extended by the Environmental Protection Agency until at least 2014. In 2013 it was planned to revise the action plan timetable to give the active conservation measures a boost.

The collaboration with Nordens Ark, which had been breeding the species in captivity for several years, was an important part of this continuing work. A total of 34 individuals were ‘born’ during 2012 in the so-called ‘hatching boxes’. The idea is to rear enough of the species to allow releases to take place at a few sites in Sweden. An attempt was made to place hatching logs in Uppsala county (Båtfors), but so far, unfortunately, it has not been successful. Any larvae that might have lived in the old oak trunks probably died before hatching time arrived. The firmest strongholds in Stockholm county are now within the National City Park (north and south Djurgården). Carefully managing these sites, therefore, is currently the priority. Collaboration with the Royal Djurgården Administration and the municipality is ongoing on issues relating to conservation and management of oak woodlands.

We have also worked actively on so-called wood depots, whereby blown-down (and felled) oaks are collected as a resource for lower invertebrate fauna. There are now two such oak depots at Djurgården. In addition, we are working on spreading information about the species and its needs. Some oaks that are particularly valuable as colony trees are kept under special surveillance. In some cases we’ve used protective netting to deter predation from woodpeckers, which would otherwise devour the rare beetle larvae. The objective is to expand the inventory of Djurgården so we have a better idea of which colony trees we have there, and also of how regeneration of old oaks is progressing. After all, we have to take a long-term view to be sure the species has suitable habitats far into the future.

If you’d like to learn more about the longhorn beetle, you’ll find an information folder from the county administrative board here.

Mats Gothnier
Action Plan for Endangered Species in Stockholm