Zoo Knoxville is mourning the loss of Dolly, a 56-year-old Southern white rhinoceros and the the oldest rhino in the United States, who was humanely euthanized following a decline in the rhinoceros’ mobility.

The oldest rhinoceros in the United States has died at a Tennessee zoo. Dolly was 56 years old. In a social media post Thursday, Zoo Knoxville said Dolly was euthanized after her mobility declined significantly in recent days despite receiving old-age medical care for some time.

Dolly the Southern white rhino had to be euthanized due to medical issues at the Tennessee zoo where she had lived since 1976. Screengrab from Zoo Knoxville's Facebook post A 56-year-old rhinoceros, the oldest in the U.