If you had asked Thomas Hildebrandt a decade ago whether the northern white rhinoceros could be saved, his answer would have been grim. The rhino’s numbers had dwindled to single digits, and the few remaining individuals all had severe reproductive issues.

“We thought, ‘The story’s over,’” said Dr. Hildebrandt, a wildlife reproductive biologist at the Leibniz Institute for Zoo and Wildlife Research and the Free University of Berlin. His prognosis got even bleaker when Sudan, the last male of the subspecies, died in captivity last spring.

But on Wednesday, Dr. Hildebrandt and a team of colleagues reported in the journal Nature Communications that the story of the northern white rhino is not, in fact, over.

Using frozen sperm from northern white rhinos and eggs from closely related southern white rhinos, the scientists created hybrid embryos that can potentially be implanted into surrogate southern white rhino mothers.