MINNEAPOLIS (WCCO) — The Lake Superior Zoo announced that a 15-year-old Amur tiger named Lana has been humanely euthanized after a brief battle with liver disease.

Lana was diagnosed with liver disease in September, and had been receiving treatment.

She showed a positive reaction to the medication, but over time caretakers noticed a change in her behavior, along with a decreased appetite.

The zoo’s Facebook page says that the tiger was not acting like herself on Wednesday. She was “extremely lethargic and did not eat her morning diet.”

At that time, the veterinarian staff made the decision to euthanize her due to the diminished quality of life.

Lana was born at the Minnesota Zoo in 2004 and cared for after her mother rejected her. She arrived in Duluth in November 2015.