But their future is at stake. Of the fifteen species of crane worldwide, most are considered endangered. Only two rapidly shrinking populations of snow cranes remain in the wild, along with a few hundred animals in breeding programmes. The cause? Us humans. Wetlands are being drained, dams are being built, breeding habitats are disappearing, and migration routes are being blocked.

What makes rescue even more difficult is that crane sperm loses its fertilising capacity after just a few days of artificial insemination. Breeding programmes often produce offspring from behaviourally incompatible pairings – when animals do not accept each other or are not compatible in terms of timing. In small populations, where every chick counts, this becomes an existential problem.

This is where a solution comes into play that sounds like something from the future, but has been working for a long time: cryopreservation. At minus 196 degrees Celsius in liquid nitrogen, sperm can theoretically be stored indefinitely – a genetic backup for endangered species.

The advantage: both sperm collection and artificial insemination are relatively straightforward and gentle procedures in cranes. However, each species is unique. For cryopreservation to work, a tailor-made protocol must be developed for each crane species: what protective substances does the sperm need? How quickly must it be frozen?

A mobile laboratory and a mission

In Gnevkow, Mecklenburg-Western Pomerania, two private owners care for 13 of the 15 crane species – a treasure that is virtually unique in the world. Together with them, the Leibniz Institute for Zoo and Wildlife Research is developing species-specific protocols for cryopreservation of sperm and artificial insemination.

A mobile sperm laboratory with a freezing unit, analysis system and transportable nitrogen containers is used. One parameter is crucial: sperm motility after thawing – in other words, how many sperm are still moving. This determines whether live chicks can be produced.

The results so far are promising: depending on the species, sperm motility after thawing ranges between 18 and 50 percent. Results of 30 to 50 percent have already been achieved for the grey crane, black-necked crane, snow crane and black-crowned crane. For other species, the results are only ten to 20 percent so far – further optimisation is ongoing here.

The next steps: From sample to biobank

What is planned for the coming years 2026 and 2027 sounds ambitious – and indeed it is:

The protocols are being further developed, especially for species with lower motility. At the same time, the Leibniz-IZW is creating a biobank for endangered crane species – a genetic treasure trove for future generations. High-quality frozen semen is used for targeted insemination to prove that this not only works on paper, but also produces real chicks.

Genetic analyses to determine paternity provide clear evidence of success. At the same time, they show which lines are particularly valuable and where breeding measures are most urgently needed. Biobanking standards are being established to ensure that the system remains stable and internationally compatible in the long term.