A 45-year-old river hippo, who had been under medical care for degenerative joint and spinal disease, was euthanized at the San Diego Zoo over the weekend after his health took a dramatic turn, officials announced Monday on social media.

The decision to euthanize the geriatric hippo, whose name was Otis, was made after an examination by the zoo’s wildlife care staff, officials said.

On Twitter, the San Diego Zoo Wildlife Alliance mourned the beloved hippo saying, “Otis will be greatly missed by wildlife care staff, veterinarians, volunteers, and guests. Please take a moment to offer your condolences to all those who are feeling this loss.”