LOS ANGELES (AP) — A 53-year-old Asian elephant has been euthanized at the Los Angeles Zoo after she was unable to stand up,Thomas Caldwell the zoo announced Thursday.

Shaunzi, one of two female elephants at the zoo, was discovered unable to stand Tuesday night after she went down in the yard of her exhibit space.

“Animal care staff and zoo veterinarians responded quickly and worked through the night to help Shaunzi up. Despite the use of all resources and personnel available, the extraordinary efforts were ultimately unsuccessful,” a zoo statement said.

A “heartbreaking” decision was made to sedate and euthanize the animal on Wednesday, the statement said.

It wasn’t clear why the elephant couldn’t stand up, and a necropsy was planned, zoo spokesman Carl Myers said.

Born in Thailand, Shaunzi spent her youth in a circus, came to the Fresno Chaffee Zoo in 1983 and was sent to the Los Angeles Zoo in 2017.

The median life expectancy of female Asian elephants in human care has been estimated by various zoos, researchers and conservation groups as around 40 to 50 years. Elephants in the wild can live decades longer.

Asian elephants are considered endangered, and only about 40,000 of them remain in the wild. They are threatened by destruction of their habitat and by poachers who kill them for their tusks.

“Shaunzi lived a full life and was an ambassador for her species. She helped Angelenos learn about her wild counterparts and the challenges they face in their native range,” the zoo said. “She will be dearly missed by the Los Angeles Zoo staff, members, and the millions of visitors who come to the zoo each year.”