A distressing account of extinction in real time, “Kifaru” follows the lives of two young Kenyan recruits who join Ol Pejeta Conservancy's rhino-caretaker unit, a small group of rangers that care for and protect Sudan, the last male northern white rhinoceros — or kifaru, in Swahili. Although Sudan is quite old, the team zealously protects him and the two remaining female northern white rhinos from poachers, with the faint hope that science can somehow find a means to save the species. The rangers have made their mission personal, treating the rhinos as immense pets — running and playing with them, rubbing them with mud, fretting when they become sick. But their devotion comes at a cost: One of the rangers, JoJo, clearly loves Sudan and the others but is torn because the job requires his absence from his family for 10 months at a time. Offering a privileged view through the eyes of the recruits, “Kifaru” spans the caretakers’ first four years on the job and provides firsthand experience of the joys and pitfalls of conservation.