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.

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, a southern white rhino, was born in 1968 at the Hluhluwe-Imfolozi Park in South Africa. She had lived at Zoo Knoxville since 1976 and was one of the first white rhinos housed at the zoo. The zoo said Dolly raised 10 calves over her lifetime and was considered a “successful mother.