Northern white rhinos face extinction

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)