One of the four surviving endangered northern white rhinos has died at a San Diego zoo in the United States.
The rhino named Nola, was put down at the San Diego Zoo Safari Park after suffering from a bacterial infection and age-related health issues. Nola had been living in the zoo since 1989.
Efforts to conserve the near-extinct species now remain uncertain as only three are now left on earth.
The three, all elderly, are kept under close guard at the Ol Pajeta Conservancy in Kenya.
