The recent attack by a captive orca on its trainer at a SeaWorld facility in Orlando, Florida, has again raised questions about our relationship with these top marine predators.
No-one knows what triggered the latest incident, and experts agree that it is almost impossible to determine why the orca, called Tilikum, reacted as it did.
But it does highlight the tensions that occur when we choose to interact closely with these huge animals.
It is also debatable what to do with those orcas, also known as killer whales, that remain in captivity.
“They are highly social animals that tend to live in cohesive groups, so it’s quite an artificial environment to capture them and put them in a small area,” says Dr Andrew Foote, an expert on wild orcas from the University of Aberdeen, UK
“The tragic events are a reminder that orcas are wild, strong and often unpredictable animals,” says Danny Groves, of the Whale and Dolphin Conservation Society (WDCS).
Reports differ, but there have been up to 24 attacks by captive orcas on people.
Contrary to popular perception, attacks by wild orcas on people have also been recorded, though no-one has been hurt.
Researcher Chris Pierpoint of the Marine Mammal Observer Association was working in Antarctica when he once subjected to a rather sophisticated, planned attack by a group of orcas.
Wild orcas in the region cooperate to hunt by swimming together towards seals resting on ice floes.
As they do so, they create a bow wave that washes the hapless seal from the ice and into the water.
“Chris Pierpoint had that done to him when in a rib in Antarctica,” says Dr Foote, though he wasn’t thrown overboard.
“A famous incidence occurred in the 1960s when a surfer was knocked off his board, but he was fine, the whale didn’t bite.”
A couple of years ago in Alaska, a child swimming in the sea also described how an orca made a bee-line toward him, before aborting a supposed attack at the last minute.
One idea is that air bubbles in neoprene wetsuits can confuse the echolocation of orcas, so they do not realise that they are approaching a person.
But the scarcity of such attacks underlines the difficulty in pinpointing their cause.
“It’s really isolated incidences. Killer whales live in cold water so they don’t overlap with people much,” says Dr Foote.
Send them home?
What the latest attack by a captive orca reveals is just how little we still know about the animals, in captivity and in the wild.
For example, we are only just glimpsing how intelligent orcas really are and the complexity of their society.
However, few insights come from studying captive whales, though some have helped reveal their acoustic behaviour.
“The science doesn’t justify the captivity. One thing I would hope is that this unfortunate incident might lead to a considered discussion on phasing out these marine parks.”
So what can or should be done with captive orcas?
One option would be to prevent further deaths by restricting trainers from encroaching too close to the poolside.
Another would be to put down any whale considered too dangerous to be kept in captivity.
The final option, and that which on the surface appears the most palatable from an animals rights perspective, is to release those whales still in captivity back into the wild.
The WDCS has repeatedly called for captive whales to be returned, not least because captivity appears to drastically reduce their life expectancy.
But that is not as simple as it sounds.
A study published by US and Danish scientists last year in the journal Marine Mammal Science documents the attempts to return a killer whale named Keiko from captivity back to the ocean.
Captured in 1979 as a near two-year-old calf, Keiko found fame as the star of the 1993 family film Free Willy, after which public pressure grew to release him back to the wild.