Researchers say they have successfully created another embryo of the nearly extinct northern white rhino in a global effort to keep the species alive. Just two animals remain, and both are female.

Nigeria’s top candidates on Saturday condemned the surprise last-minute decision to delay the presidential election for a week until Feb. 23, blaming each other but appealing to Africa’s largest democracy for calm. The decision, announced five hours before polls were to open, is a costly one, with analysts at SBM Intelligence estimating an economic hit of $2 billion, plus a...