In December 2013, the northern white rhino Nabire walks around in her enclosure at a zoo in Dvur Kralove, Czech Republic. Nabire died of a ruptured cyst in July 2015, leaving only a few northern white rhinos left in the world.
In Kenya, where three of the remaining northern white rhinos live, armed guards prevent poaching.
Brent Stirton/Getty Images
Sudan was one of three northern white rhinos left worldwide. He died in March 2018.
Ol Pejeta Conservancy
As the only male, the fate of the subspecies depended on Sudan. Though he was too old to mate, scientists are hoping to impregnate other females using his sperm.
In addition to round-the-clock security, the conservancy has put radio transmitters on the animals and dispatches incognito rangers into neighboring communities to gather intelligence on poaching.
Courtesy Chris Morrow
Rhinos are targeted by poachers, fueled by the belief in Asia that their horns cure various ailments.