Dulary, an Asian elephant that spent more than 40 years living at the Philadelphia Zoo, died Monday at The Elephant Sanctuary in Hohenwald, Tenn. She was 50.

Employees said Dulary showed no recent indications of illness until early Sunday morning, when she was found lying down in the sanctuary's Asian barn. Though members of the elephant care team were immediately alerted, they were unable to help Dulary stand.

Veterinarians at the Philadelphia Zoo were called for consultation, and Sanctuary employees monitored Dulary through the night as diagnostic tests were performed. Despite the efforts, "Dulary passed away peacefully on Monday morning, surrounded by those who loved her," according to a news release from The Elephant Sanctuary and Philadelphia Zoo.

Those loved ones included Dulary's best friend, an elephant named Misty. Employees left the barn Monday to give Misty some time to spend alone with her departed companion.

Though Dulary was experiencing intermittent health issues at the beginning of this year, sanctuary staffers created a treatment plan that included multiple medications and a custom-made "elephant corset" crafted from burlap coffee bags. She soon recovered and in May celebrated her 50th birthday. Sanctuary workers said Dulary was active and had a good appetite in recent months.

Dulary was brought to the Philadelphia Zoo in 1964, a year after her birth. She was relocated to the sanctuary in May of 2007 after the zoo found it had insufficient funding to build a new elephant habitat capable of housing an expanded herd.

Staffers said the pachyderm "easily assimilated" into life at the sanctuary, where she and elephants Misty and Delhi "became an inseparable group." Misty and Dulary comforted one another following Delhi's passing in 2008. After that, the duo rarely spent time apart until Dulary's death.

"In India, 'Dulary' is a term of endearment intended for someone who is an object of great affection and love, and our Dulary will always hold a special place in our hearts," according to the release. "Strong-willed and self-confident, she was a treasured member of the Philadelphia Zoo community and The Elephant Sanctuary family, and she lived her life to the fullest every day. She will be remembered with joy by all of those whose lives she touched. We are honored to have been a part of her journey."