Great capricorn beetle conservation

Great capricorn beetle is one of Sweden's rarest and most endangered insects. Its distribution area used to extend from Skåne, Blekinge, eastern Småland to Öland, but is now only found in one place in Sweden; namely in the nature reserve Halltorps hage on Öland. The species is already extinct in Denmark, Belgium, Holland, Luxembourg and Great Britain.

The absolute number one threat to great capricorn beetle is the loss of suitable habitat. The larvae live in living, very old oaks with thick bark and during the 1850s millions of such oaks were felled in meadows and pastures. This, together with the regulation of rivers and a general overgrowth of grazed oak forests, has led to the sharp decline of the species. Bigger is today classified as Critically Endangered on the Swedish Red List and Vulnerable on the IUCN Red List.

Old dead oak on Öland.

What we do at Nordens Ark

Since 2012, Nordens Ark has worked actively with the conservation of the great capricorn beetle. The work takes place in collaboration with the County Board in Kalmar and Blekinge counties, and within the framework of the national action program.

In order to re-establish the great capricorn beetle on the Swedish mainland, Nordens ark has developed a unique breeding method. A challenging task as there was no previous experience of breeding the species on a large scale, but after three years of hard work we finally had a working method. The species has three life stages; larva, pupa and beetle, where each stage requires a special treatment. The larvae are reared in petri dishes filled with a nutrient-rich food mixture mainly based on oak shavings. There, the larvae eat and grow large for two years until it is time to transition to the pupal stage. The pupae hatch into fully formed beetles a month later at the end of summer. The beetle must overwinter in a refrigerator to complete its life cycle and become reproductive.

Eggs are picked from pieces of logs in Nordens Ark's breeding facility.

With this method, we can now annually produce 150–300 great capricorn beetle for release. The first releases on the mainland took place in 2017 in Björnö and Tromtö nature reserves. Thanks to extensive restorations, there are now large contiguous oak environments and good conditions for the species to gain a foothold. Since 2017, 900 great capricorn beetles have been able to be released, which has given good results. Namely, in 2022 the first hatching holes of great capricorn beetles were found on oaks where releases had previously taken place. It is a first sign that we have succeeded in re-establishing the species in its former range!

News from the project - March 2024

In 2023, a total of 95 great capricorn beetles could be released in Björnö nature reserve in Kalmar county and Tromtö nature reserve in Blekinge county.

A very positive piece of news from this year's release season is that a newly hatched male great capricorn beetle was found in the release area in Björnö nature reserve. In addition, several new hatching holes have been discovered in the area. The species has been missing from the reserve for the past 50–100 years. The newly hatched male and new hatching holes are a direct result of the last 6 years' releases of great capricorn beetles in the area have worked.

Great capricorn beetle larva.

In collaboration with

Kalmar and Blekinge county administrative board.