Over the past 35 years, America’s most famous living killer whale has shouldered a fraught history, emerging as the symbol of both orcas’ elegance and their capacity for violence. As the focus of the 2013 documentary “Blackfish,” Tilikum — affectionately called “Tili” — has been at once regarded as a victim of captivity and a maker of tragedy.

On Tuesday, SeaWorld Orlando announced that his knotty story may be coming to a slow and quiet end.

The marine park, which has owned Tilikum for more than two decades, said in a statement on its website that he is suffering from an illness that probably may take his life.

“Despite the best care available, like all aging animals, he battles chronic health issues that are taking a greater toll as he ages,” SeaWorld said. “Our teams are treating him with care and medication for what we believe is a bacterial infection in his lungs. However, the suspected bacteria is very resistant to treatment and a cure for his illness has not been found.”

Scott Gearheart, a staff veterinarian, teared up while discussing Tilikum’s prognosis in a SeaWorld video.

“I wish I could say I was tremendously optimistic about Tilikum and his future,” Gearheart said, his voice cracking. “But he has a disease which is chronic and progressive, and at some point might cause his death.”

The veterinarian added: “If he would have shown up with this disease in the wild, there’s no doubt in my mind he’d have been gone a long time ago.”

Male orcas in the wild have an average life span of 50 to 60 years, but the expectancy for killer whales in captivity is much shorter. Tilikum is believed to be about 35 years old; the median survival rate for orcas in U.S. marine parks is just 12 years.

If Tilikum passes away, he will be remembered for a number of things: the three human deaths — among them, the violent passing of SeaWorld darling Dawn Brancheau — to which he has been linked, the documentary that spurred a movement to have him freed and the complicated questions he has inspired about humans’ relationship to the animals we attempt to control.

Before Tili, there was Namu, the first orca to be captured and trained in the United States. Then there was Shamu (a portmanteau of “she” and “Namu”), who starred in eponymous and iconic killer whale shows. And who could forget Keiko, the orca who played the title character in “Free Willy”?

Yet none of these former aquatic stars has attracted quite the same mixture of scandal and sympathy as the energetic killer whale whose name means “friend” in Chinook.

In November 1983, Tilikum was found with two female orcas in the icy waters of west Iceland. He was netted as part of an extensive capture network organized by Don Goldsberry, who created the original Shamu shows with Ted Griffin.

According to Outside Magazine, the killer whales were housed in a concrete holding tank for nearly a year before being transferred to Sealand of the Pacific, a marine park near Victoria, British Columbia.

The conditions at Sealand were poor. The killer whales were confined to pools less than 20 feet deep, and Tilikum had to contend with two aggressive roommates (females are dominant in the orca world).

It was there that the first death occurred.

Eight years after Tilikum and the two female orcas were taken from the wild, a 20-year-old part-time trainer named Keltie Byrne slipped and fell into their tank.

“She tried to get back out and the other girl tried to pull her up, but the whale grabbed her back foot and pulled her under,” a witness told CNN in 1991. “And then the whales — they bounced her around the pool a whole bunch of times, and she was screaming for help.”

Byrne, a marine biology student and a competitive swimmer, had plenty of experience in water. But none of that matter when faced with several tons of killer whale.

Byrne drowned before anyone could save her.

She was the first trainer to be killed by orcas at a marine park, Outside reported, but she wouldn’t be the last, or even the last one with which Tilikum would come into contact.

And yet, a former employer at Sealand recalled to CNN that Tilikum was very “easy to work with.”

“He was very easygoing, he learned quickly,” Colin Baird said. “You know, he was probably my favorite of the three.”

Sealand’s business prospects never recovered from the incident. They closed in 1992, a year after selling their killer whales to SeaWorld.

To observers, it may have seemed a curious decision on SeaWorld’s part. After all, why would they want three orcas that had just involved in a high-profile tragedy?

A major factor was Tilikum’s virility. In an attempt to distance itself from capture methods that were coming under fire, SeaWorld was focusing its energies on establishing a strong captive breeding network. The park discovered that Tilikum had impregnated both of the female orcas at Sealand, indicating that his sperm could be of great use.

Today, Tilikum is regarded as prolific in his capacity for insemination, having sired 21 offspring (10 of which are still alive).

But even this achievement has been questioned. Given his violent tendencies, was it a good idea to share his genes? As The Washington Post’s Michael O’Sullivan wrote in his review of “Blackfish,” “A dog that had bitten that many people would have been euthanized long ago and not sent to a stud farm.”

SeaWorld was a major upgrade for the Sealand killer whales, with some of the best facilities for marine animals in the world. And yet, the fatalities continued.

In 1999, the limp body of 27-year-old Daniel Dukes was found lying across Tilikum’s back. He had recently been released from a county jail, and appeared to have snuck into the park at night. By the time they found Dukes, he had died from drowning.

Ric O’Barry, a marine mammal trainer of 40 years, told Orlando Weekly that regardless of what caused Dukes’s death, the orcas’ lifestyle was less than ideal, despite SeaWorld’s numerous amenities.

“They’re bored,” O’Barry said of the killer whales. “We literally bore them to death. It’s like you living in the bathroom for your life.”

Experts say it was something more than boredom, however, that led to the death of star trainer Dawn Brancheau.

The word orca researcher Ken Balcomb used in “Blackfish” was “psychotic.”

Brancheau had wanted to work with killer whales since she was nine years old, when she took a trip to SeaWorld with her family, Outside reported. She trusted the animals, she was comfortable around them, and, at age 40, the “vivacious” blond was “literally the poster girl for the marine park…appearing on billboards around the city.”

In February of 2010, Brancheau had just completed a show and was feeding Tilikum when he suddenly grabbed her by the hair and started “thrashing” her around the tank, the Associated Press reported at the time.

To many onlookers, the attack looked deliberate. “We don’t know for sure what motivated Tilikum,” former trainer Jeffrey Ventre told Outside. “But there’s no doubt that he knew exactly what he was doing. He killed her.”

As with the others, Brancheau was dead by the time they got ahold of her body.

Tilikum was retired from doing shows, but not for long. He returned to public performances in the spring of 2011. Two years later, “Blackfish” was released, documenting the plight of killer whales at marine parks across the country.

Tilikum instantly became a cause for viewers, who called for his release and rallied around the demand to “Free Tilly,” despite the difficulties of ensuring a captive orca’s survival back in the wild.

SeaWorld condemned the documentary as “propaganda,” stating in a lengthy response that “the film conveys falsehoods, manipulates viewers emotionally and relies on questionable filmmaking techniques to create ‘facts’ that support its point of view.”

Notwithstanding his troubling, controversial history, the trainers featured in the video announcing Tilikum’s illness were emotional about his deteriorating health.

Daniel Richardville, who has worked with Tilikum for a decade, concluded: “These are the ups and downs of the life we have been living with him.”

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