Researchers at the San Diego Zoo Safari Park believe a change in diet could be behind a southern white rhino baby boom. On April 30, a southern white rhino named Kiazi gave birth to her first calf, following 16 years of regular breeding. After nine years of study, scientists at the San Diego Zoo Institute of Conservation Research discovered that southern white rhinos born in zoos are often infertile, and that's likely due to compounds, called phytoestrogens, that are found in the soy and alfalfa they are fed.