Researchers are to attempt to rear swallowtail butterflies from eggs frozen in liquid nitrogen in a test to see whether cryopreservation could support the long-term conservation of Britain’s largest native species.

In a groundbreaking project, researchers will freeze eggs of captive-bred European swallowtails in liquid nitrogen at -196C and attempt to rear butterflies from the unfrozen eggs, comparing their success with butterflies reared from eggs that have never been frozen.

If the method is successful, it could lead to eggs of the British swallowtail being stored to support long-term conservation strategies, such as breeding programmes and translocation efforts.

The British swallowtail (Papilio machaon britannicus) is a unique subspecies but its range is shrinking and it is vulnerable to extinction, confined to low-lying parts of the Norfolk Broads likely to be overwhelmed by rising seas over the next century. In 2024, it suffered its worst year since scientific records began.

Cryopreservation for butterflies is being tested by researchers from Anglia Ruskin University (ARU) in partnership with Jimmy’s Farm & Wildlife Park and Nature’s Safe charity, a biobank specialising in conservation cryopreservation.

Dr Alvin Helden, a member of the Applied Ecology Research Group at ARU, said: “Our project will combine fieldwork and lab research to see if we can establish a reliable method for preserving the British swallowtail’s genetic material by using its closely related, but less endangered, European cousin. Cryopreservation is a promising tool for supporting conservation efforts, but we believe this is the first time it has been attempted with butterflies.”

Jimmy Doherty, founder of Jimmy’s Farm & Wildlife Park, which houses a thriving captive population of the European swallowtail (Papilio machaon gorganus), said: “Our commitment to the science of entomology, and especially butterfly conservation, means this project is a natural fit for us. Partnering with ARU and Nature’s Safe allows us to apply our expertise to work that could make a real difference in protecting the British swallowtail for generations to come.”

Debbie Rolmanis, chief operating officer of Nature’s Safe, said: “This project holds significant importance for the development of cryopreservation techniques – not only for the British swallowtail, but across pollinators and invertebrates as a whole.”