Northern white rhinos face extinction
Northern white female rhino Nabire, right, is shown at a Czech Republic zoo in 2011. At left is Natal, a southern white rhino. (Petr David Josek / Associated Press)
A northern white rhino in 1995 at the San Diego Zoo Safari Park, known then as the Wild Animal Park. (Bob Grieser / Los Angeles Times)
Fatu is under observation at a Kenyan preserve. Keepers say they doubt the extremely endangered rhinos there will ever reproduce naturally. (Ben Curtis / Associated Press)
Fatu, a female rhino shown in December 2014, is let out of her pen to graze at Ol Pejeta Conservancy in Kenya. White rhinos are the second-largest land mammal, the World Wildlife Fund says. (Ben Curtis / Associated Press)
Najin is a female northern white rhino at the Ol Pejeta Conservancy in Kenya. (Ben Curtis / Associated Press)