SeaWorld, which has come under harsh criticism for its whale acts, is phasing them out. With Kayla's death, it has 20 whales between its three parks.
A 30-year-old female whale died Monday at SeaWorld in Orlando after suddenly falling ill over the weekend, park officials said.
Kayla — who prior to her death was the second-oldest whale ever born in captivity — first showed signs of not feeling well on Saturday, SeaWorld said.
Her condition quickly worsened before her dying "with her animal care specialists by her side" at 12:15 a.m. ET on Monday, according to a statement by SeaWorld.
"Her veterinarians immediately began treatment based on a physical examination" on Saturday, SeaWorld said. "Unfortunately, her condition worsened through the next two days. Although animal care specialists and veterinarians devoted around the clock attention to Kayla, she did not survive."
Results of a postmortem exam to determine Kayla's cause of death could take several weeks.
"The entire SeaWorld family is deeply saddened by the loss," according to the statement.
Naomi Rose, a marine-mammal scientist at the Animal Welfare Institute and frequent critic of SeaWorld, said the mean age of a whale who survives the first few months of life is about 50.
"She shouldn't be dead, she should be in the prime of her life," Rose told NBC News on Monday.
The company announced back in 2016 it is phasing out whale acts, by no longer breeding or acquiring any more of the massive mammals. Following Kayla's death, SeaWorld has 20 whales left at its parks — five each in Orlando and San Diego and 10 in San Antonio.
The youngest whale in SeaWorld's care now is a 4-year-old in San Diego.
SeaWorld had been pressured to end its whale operation in the aftermath of the 2013 documentary "Blackfish," which questioned the morality of keeping them in captivity.
The 2010 death of trainer Dawn Brancheau, at the hands of SeaWorld orca Tilikum, was a focus of the movie.