Blue, a cougar who had lived at Stone Zoo in Stoneham since he was a cub, died on Saturday, the zoo said in a press release. After months of seizures, 9-year-old Blue was responding well to treatment.

A 9-year-old cougar at Stoneham’s Stone Zoo was euthanized Saturday after its ongoing battle with seizures. Blue began experiencing seizures several months, a press release from the Stone Zoo said.