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.