Cerambyx cerdo is a threatened longhorn beetle (Cerambycidae) which inhabits living old sun-exposed oak trees with thick bark. In these old oaks the species seem to live for centuries. C cerdo also colonise sun-exposed middle-aged oak trees in bad condition with a low vitality. In many cases the oaks die and the species has to find new trees to live in. There are however also examples where the colonised middle-aged oaks have survived and gained a much better vitality with the result that C cerdo has ceased to live in the trees. Larval development take place both beneath the bark and in the sapwood. In Sweden larval development is thought to take five years. Adults (imagines) leave their host trees in June. As soon as the adults leave the host trees reproduction take place. The adults are occasionally observed feeding on sap-flows. Many adults die quickly as they get predated by birds but occasionally adult individuals have been observed as late as in September.
The last remaining site with C cerdo is Halltorps hage on the island of Öland, in southeast Sweden. C cerdo is extinct on the Swedish mainland since about fifty years, probably mainly because old sun-exposed oaks have decreased continuously during the last 200 years due to logging of old oak trees, regulation of some large rivers and ceased grazing of oak woodlands. Regulation of the rivers stopped flooding and led to dense forests, and the competition advantage for the oaks disappeared. Formerly more open standing oak trees died from competition from other tree species like e g spruce and the recruitment of new oak trees stopped.
The short term conservation objective in Life BTG is to reintroduce C cerdo in the project sites Björnö and Tromtö-Almö on the Swedish mainland, within its former range, and in accordance with the national species action plan for the period 2015-2019. This will be done within the frame-work of a long term conservation objective to reintroduce and re-establish C. cerdo populations in four different oak landscapes. The goal is that the total Swedish population will exceed 500 active adult beetles per year in 2040, as estimated by counting the exit holes on tree trunks.