Angalifu, was only one of six rhinos left in the world died on San Diego Zoo Safari Park. (Associated Press)
A rare species of rhinoceros is one member closer to extinction after one of only six surviving animals died, zoo keepers said on Monday.
Northern white rhinoceros Angalifu, believed to be 44 years old, died on Sunday at San Diego Zoo possibly of old age, said spokeswoman Darla Davis, adding that post-mortem results were pending.
The only members of the species left now are an elderly female in San Diego, three in Africa and one at a zoo in the Czech Republic.
Zoo keepers in the southern Californian zoo had tried unsuccessfully to persuade their two northern white rhinos to mate.
The northern white rhino has been nearly wiped out by hunting and poaching for their horns, and by wars in Africa, according to the World Wildlife Foundation.