Lucy the elephant, believed to be the world's fourth-oldest African elephant in captivity, was euthanized Friday morning after staffers found her lying down in her stall, the Milwaukee County Zoo said.

The medical staff had recently decided that if the 46-year-old elephant were found lying down again, she would be euthanized, spokeswoman Jennifer Diliberti said.

In June, Lucy became ill and was unable to stand up in the African exhibit yard. A crane was brought in to lift the 9,000-pound animal to her feet; she struggled for a few days after that but improved.

Diliberti said Lucy was found lying down in late July but was able to get up on her own.

Brittany, Lucy's companion and the only other elephant at the zoo, was allowed in Lucy's stall after she was euthanized so she could grieve, Diliberti said.

She said the zoo hopes to get another elephant soon as a companion for Brittany, who is in her late 20s. Lucy spent 44 years at the zoo.

"It's just so sad but she had a good, long life here so that's good," Diliberti said.