Northern white rhinos are critically endangered and up until recently, there were 6 of them that were known to be alive in the entire world. A northern white rhinoceros that was living at the San Diego Zoo Safari Park died on Sunday.

Northern white rhinos are critically endangered. Up until recently, only six were known to be alive in the entire world.

Now the population count has been reduced to five. A northern white rhinoceros that was living at the San Diego Zoo Safari Park died on Sunday.

44-year-old Angalifu passed away from old age. The facility’s curator released a statement noting that the rhino's "...death is a tremendous loss to all of us. Not only because he was well beloved here at the park but also because his death brings this wonderful species one step closer to extinction."

Only one northern white rhino remains at Safari Park. Zoo staffers had previously tried to get Angalifu and the female rhinoceros, Nola, to mate, but were unsuccessful.

No sightings or evidence has surfaced indicating there are more of the Northern white rhinos living in the wild. About 4 decades ago, there were about 500 in the wild, but poaching has played a major role in the significant population decline. Currently, all remaining northern white rhinos are in captivity.