Woodland Park Zoo euthanized a 47-year-old, female hippo March 24 due to physical decline from age-related osteoarthritis.

Despite medication, the hippo, named Gertrude, experienced intense generalized lameness, which seriously affected her mobility and compromised the quality of her life, according to a Woodland Park Zoo press release.

Gertie, who weighed approximately 5,000 pounds, lived at the zoo since 1966. She was the oldest animal currently living at the zoo and is believed to have lived at the zoo longer than any animal in its 110-year history.

Two female hippos remain at the zoo’s African Savanna: 31-year-old Water Lily and 10-year-old Guadalupe.

According to Dr. Darin Collins, the zoo’s director of Animal Health, the hippo’s health had been under a normal age-related decline for the last year from the degenerative joint disease, not uncommon in geriatric animals, including humans.

During the past few months, the zoo’s animal management and animal health staff had been closely monitoring her mobility, condition and pain levels. Her condition worsened significantly in the last week as her mobility became challenging and discomfort more apparent, according to the zoo press release.

“We could no longer medically manage her pain and we had to follow her cue that the quality of her life was becoming seriously compromised,” Collins said in the press release. “Therefore, we had to make the difficult, but humane, decision to euthanize her.”

Hippos can live up to 49 years in zoos. The life expectancy of hippos is 45 years in the wild.

“For more than 44 years, Gertie has delighted zoo visitors of all ages and helped teach them about these impressive animals," Martin Ramirez, mammal curator at the zoo, said in the press release. "You could truly say she was an icon at the zoo. It is with a heavy heart that we say good-bye to Gertie."