The birth of a southern white rhino at San Diego Zoo this week has been hailed as an historic milestone which could help save another subspecies from extinction.
The calf was conceived after its mother, Victoria, was inseminated with frozen sperm.
Conservationists are now hopeful that the process could be repeated with northern white rhinos, of which only two — both female — are still alive today, although sperm has been frozen.
"The Southern White Rhinos here are going to be eventually surrogate mothers for embryos for Northern White Rhinos," Dr Barbara Durrant, Director of Reproductive Sciences for the San Diego Zoo Global said.
"So there are several significant things here: one is that we had a successful birth, another is that this success is the result of artificial insemination with frozen semen, the first in North America to be a successful birth. And it’s also significant that now we know that Victoria is capable of conceiving and carrying an embryo to term, giving birth, and nursing an offspring," she added.