SAN DIEGO (AP) -- A southern white rhino has become pregnant through artificial insemination at the San Diego Zoo Safari Park -- giving hope for efforts to save a subspecies of one of the world's most recognizable animals, researchers announced Thursday.
Scientists will be watching closely to see if the rhino named Victoria can carry her calf to term over 16 to 18 months of gestation.
If she does, researchers hope someday she could serve as a surrogate mother and could give birth to the related northern white rhino, whose population is down to two females after decades of decimation by poachers. The mother and daughter northern white rhinos live in a Kenya wildlife preserve but are not capable of bearing calves.
News of Victoria's pregnancy was confirmed two months after the death of the last northern white male rhino named Sudan, who was also at the Kenya preserve and was euthanized because of ailing health in old age.
Victoria is the first of six female southern white rhinos the San Diego Zoo Institute for Conservation Research is testing to determine if they are fit to be surrogate mothers. If she and the others are deemed fit to do so, they could carry northern white rhino embryos sometime within the next decade as scientists work to re-create northern white rhino embryos.
There are no northern white rhino eggs so creating an embryo would require using genetic technology. Scientists plan to use frozen skin cells from dead northern white rhinos to transform them into stem cells and eventually sperm and eggs. Then the scientists would use in vitro fertilization to create embryos that would be put in the six female rhinos.
"The confirmation of this pregnancy through artificial insemination represents an historic event for our organization but also a critical step in our effort to save the northern white rhino," said Barbara Durrant, director of reproductive Sciences at the San Diego Zoo Institute for Conservation Research.
But more challenges lie ahead, with artificial insemination of rhinos in zoos rare so far and resulting in only a few births.
Victoria is a healthy 747-pound (1,700-kilogram) rhino estimated to be seven years old.
She and the other five female rhinos that range in age from four to seven years old were all born in the wild and relocated to San Diego's Safari Park in 2015. Scientists will soon start developing artificial insemination techniques and embryo transfer techniques for them. The rhinos also undergo weekly ultrasounds.
"We will know that they have proven themselves to be capable of carrying a fetus to term before we would risk putting a precious northern white rhino embryo into one of these southern white rhinos as a surrogate," Durrant said.
While embryos have been created for southern white rhinos, they haven't been for northern white rhinos.
The San Diego Zoo Institute for Conservation Research has the cell lines of 12 different northern white rhinos stored in freezing temperatures at its "Frozen Zoo."
The ultimate goal is to create a herd of five to 15 northern white rhinos that would be returned to their natural habitat in Africa. That could take decades.
Some groups have said in vitro fertilization is being developed too late to save the northern white rhino, whose natural habitat in Chad, Sudan, Uganda, Congo and Central African Republic has been ravaged by conflicts in the region. They say the efforts should focus on other critically endangered species with a better chance at survival.
The southern white rhino and another species, the black rhino, are under heavy pressure from poachers who kill them for their horns to supply illegal markets in parts of Asia.
There are about 20,000 southern white rhinos in Africa.