COLUMBUS, Ohio (WCMH) — With no clear diagnosis, the Columbus Zoo announced it had to humanely euthanize one of its animals.

Anana, the zoo’s 15-year-old polar bear, had an unknown condition that was causing unusual behavior, and rapidly got worse over the week of Oct. 9. The Columbus Zoo said it tried some initial treatments, as well as a thorough evaluation of the bear with several local veterinary specialists.

While the team could not find a “clear diagnosis,” the zoo said it tried treating Anana for an autoimmune disorder. Her condition briefly improved before it “declined dramatically,” leading to the decision to euthanize. The Ohio State University Veterinary Diagnostic Lab handled a postmortem exam of Anana, and will provide results in the coming weeks.

Anana the polar bear (Courtesy Photo/Columbus Zoo and Aquarium).

Anana, born at the Toledo Zoo on Nov. 25, 2006, moved to the Columbus Zoo in 2010 after a stop at the Pittsburgh Zoo. She leaves behind one cub, born in November 2016, named Amelia Gray. The now six-year-old bear lives at the Oregon Zoo.

The team at the Columbus Zoo that cared for Anana said she was a “true princess,” and was the best at finding napping spots. The zoo said the polar bear was also an expert trout hunter, and an “incredible ambassador” for her threatened species.