German researchers say they have hit on a way to safeguard the world’s population of endangered Asian elephants: safely freeze the animals’ sperm. Elephants are notoriously tricky to breed in zoos, with high rates of miscarriages and infant mortality. Artificial insemination almost always fails because fresh sperm rarely survives the procedure intact. Suzan Murray, head veterinarian at the National Zoo in Washington, D.C., says an effective cryopreservation technique would “revolutionize our ability to breed and maintain elephants in zoos.” Until now, however, a successful process had not been achieved.

The latest research was conducted by the Leibniz Institute of Zoo and Wildlife Research in Berlin. A team evaluated several ways of freezing using combinations of chemicals to protect the reproductive cells. One of the methods resulted in slightly more than half the sperm testing normal. Previously “no one was really able to freeze Asian elephant sperm so that enough of the cells were alive and moving,” team member Robert Hermes says. Insemination trials will begin soon.