KNOXVILLE, Tenn. (AP) — The oldest rhinoceros in the United States has died at a Tennessee zoo. Dolly was 56 years old.

A 56-year-old rhinoceros, the oldest in the U.S., has died in Tennessee after exceeding the median life expectancy for her species by nearly 20 years. Zoo Knoxville announced Feb. 6 that Dolly the Southern white rhino had experienced severe mobility issues in recent days, leading to the decision to euthanize her.

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.