northern white rhino

Only two northern white rhinos remain, and they're both female. But researchers said Wednesday that they successfully have created embryos using sperm collected from the males before they died out.

Sudan lived most of his life in a zoo in the Czech Republic but was brought to a conservancy in Kenya in 2009 as part of a last-ditch effort to save his species. He died at the conservancy at age 45.

With the death of a northern white rhino in San Diego's zoo this week, researchers are working to see whether they can save the species. They'd better hurry — only five remain.