BERLIN (AP) — Scientists in Europe said Tuesday they've successfully transferred a test tube rhino embryo back into a female whose eggs were fertilized in vitro, as part of an effort to save another nearly extinct sub-species of the giant horned mammal.

The procedure was performed last month on a southern white rhino at Chorzow zoo in Poland, said Thomas Hildebrandt of the Leibniz Institute for Zoo and Wildlife Research in Berlin.

Hildebrandt is part of BioRescue, an international team of scientists and conservationists trying to use IVF to save the rare northern white rhino.

Only two northern...