'As the Associated Press reports, Bridget had recently started to show signs of illness: she was lethargic, she wasn’t eating and she appeared to be in pain. In a statement, the Oklahoma City Zoo said that veterinarians decided to perform an emergency examination on the lioness and found excess fluid around her heart—a sign of heart failure or infection. “Given her advanced age and the severity of her condition, the vet and caretaker teams made the difficult decision to humanely euthanize Bridget” on Wednesday, April 4, the statement says.'