Nola, one of only four known northern white rhinoceroses, died on Sunday at the San Diego Zoo Safari Park, the park said in a statement. The park said that Nola, 41, had a bacterial infection, as well as age-related health issues, and that officials made the decision to euthanize her after her condition worsened overnight on Saturday.
"We're absolutely devastated by this loss, but resolved to fight even harder to #EndExtinction," the park wrote in a Facebook post, adding, "let this be a warning of what is happening to wildlife everywhere."
The northern white rhinoceros is the most endangered animal on earth, according to the San Diego Zoo Global Wildlife Conservancy. Frequent civil wars and widespread poaching of rhinos in Africa, driven largely by demand in Asia for ground-up horns as an ingredient in medicine, has caused their numbers to plummet. Only about 29,000 rhinos remain in the wild today, down from about 500,000 at the beginning of the 20th century, according to Save the Rhino, a charity.
The San Diego conservancy estimated that three of the animals were killed each day.
Nola had lived at the San Diego Zoo Safari Park in Escondido, California, since 1989 and spent most of her time as a resident of the South Africa exhibit. A video posted to the zoo's YouTube channel in January showed her ambling slowly through the dry grasses and shallow ponds of her 65-acre enclosure, poking at the ground with her gracefully curved horn.
"For us as an institution, she probably is one of the most important animals in our collection," said Jane Kennedy, Nola's lead keeper, in the video, which briefly discussed her health problems. "What she represents is extinction."
The northern white rhinoceros originally comes from Central Africa, said Andy Blue, the associate curator of mammals at the San Diego Zoo Safari Park, in a video posted to the wildlife conservancy website.
The last three known northern white rhinoceroses live at the Ol Pejeta Conservancy in Kenya, where they roam in a 70-acre enclosure, protected by armed guards 24 hours a day. There is only one remaining male, named Sudan, and two females, Najin and Fatu. All are older and neither of the females is capable of breeding naturally, the conservancy said, while Sudan's sperm count is "disappointingly low" due to his age.