Officials said keepers found the elephant, named Watoto, lying in her yard and unable to get on her feet early Friday morning. Several attempts by zoo officials to help her stand up failed, as did an attempt using a piece of equipment to lift her.
"There hasn't been anything recently in the last couple of days that would give us any advance warning or premonition," Watoto's veterinarian Darin Collins said.
Zoo animal health officials determined Watoto was sick and her condition was rapidly worsening. They then made the decision to euthanize her.
"This is a very difficult time for our zoo family as we mourn the loss of Watoto, a beloved animal and dear friend to our staff and volunteers, members and community," Bruce Bohmke, Woodland Park Zoo's Chief Operations Officer, said in a release announcing the death. "Watoto has lived a long, healthful life at Woodland Park Zoo under the care of dedicated keepers and staff. We will all miss her greatly."
Bohmke says a full necropsy will be done and they will release their findings in a few weeks.
Watoto has been at the zoo since 1971 and is considered to be the matriarch or leader of the zoo's herd, officials said.