Zoo staff made the difficult choice to euthanize one of the zoo’s two female mountain lions, Sierra, earlier in the week. Officials said 17-year-old Sierra was suffering from advanced kidney failure.

The Phoenix Zoo lost one of its longtime residents this week. Sierra, a mountain lion, was humanely euthanized due to advanced renal failure. Sierra and her sister, Mystic, came to the zoo as cubs ...

The Phoenix Zoo lost its beloved mountain lion, Sierra, who was humanely euthanized this week after dealing with advanced renal failure. The Reid Park Zoo had to humanely euthanize their African lion, ...