Lolita, an orca held captive for more than half a century at the Miami Seaquarium, has died at the estimated age of 57 from suspected kidney disease.
Also known as Tokitae or Toki, she was believed to have been the world’s second-oldest killer whale.
Her death on Friday came as her caregivers were making preparations for her to return to the ocean in the near future.
The Seaquarium posted a statement saying the whale had “started exhibiting serious signs of discomfort” over the last two days, for which they said she had been treated “immediately and aggressively”.
They went on: “Despite receiving the best possible medical care, she passed away Friday afternoon from what is believed to be a renal condition.”
Staff went on to call her “an inspiration” and a “beautiful spirit,” highlighting the Lummi Nation (a Native American tribe based in Washington state) who they said “considered her family”.
The theme park also shared a short video on social media showing her performing tricks in her pool and interacting with her keepers.
Lolita had spent decades performing for Miami crowds after being captured in the summer of 1970, when she was around four years old, during a period of deadly orca roundups.
An orca believed to be her mother, Ocean Sun, who is now in her 90s, continues to swim free with other members of their clan in the waters between Washington state and Canada.
Animal rights activists have since spent years fighting to have Lolita – who weighs 5,000lbs (2,267kg) – freed from captivity, where she lived in a tank that was 80 ft by 35 ft and 20 ft deep.
She retired from performing last spring as a condition of the park’s new exhibitor’s license with the US Department of Agriculture and had not been publicly displayed since.