The San Diego Zoo is setting aside $2 million a year in efforts to prevent the extinction of the northern white rhino.

To date, there are only four northern white rhinos alive, and one of them, a female named Nola, is housed by the zoo. One male and two females are at the Ol Pejeta Sanctuary in Kenya.

The 41-year-old female showed no interest in mating with Angalifu, the park's male northern white rhino. Angalifu died in December at age 44.

In the last 12 months, three northern rhinos have died. One in San Diego, another in Czech Republic and one in the Ol Pejeta Sanctuary.

The recovery of the species, however, would span decades of vigorous effort and cut close to around $100 million in cost.

In the hope of imparting the vision for the northern white rhino, Randy Rieches, San Diego Zoo's mammal curator, shared the details of the project with a bunch of elementary students who were on a Safari Park visit.

"We want to be able to hand off a herd, a sustainable herd of northern white rhinos to some of these young kids here who are budding zoologists," said Rieches.

At the heart of the species revival project are six southern white rhino females, brought to San Diego all the way from South Africa. Researchers hope to be able to develop a plan for reproduction.

The southern white rhinos are highly similar to the northern white rhinos, according to San Diego Zoo researcher Barbara Durrant. The southern white rhino females can be used as surrogates for northern white rhino embryos, Durrant said.

The plan involves using DNA on file to come up with a stem cell line, and implanting an embryo in a female southern white rhino.

"It's been done in cattle, horse and humans - it's doable," said sanctuary chief executive Richard Vigne.

Researchers are careful to strike a balance between optimism, and realism for the project, as the technology they are using has yet to be adapted for larger animal species such as rhinos.

If successful, the process could be used for other endangered species.

Among the World Wildlife Fund's critically endangered species are the Amur Leopard, Black Rhino, Cross River Gorilla, Hawksbill Turtle, Javan Rhino, Leatherback Turtle, Mountain Gorilla, Pangolin, Saola, South China Tiger and Sumatran Elephant.

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