Captivity destroys their social skills
"They grow up without knowing proper social etiquette," Rose says of orcas bred in captivity, who are isolated from the crucial social support system that orca family provides. "Males...can be violent when mating," she notes. "Dominant females can assert their dominance with unnatural violence."
In 1989, an orca named Kandu violently attacked another orca at SeaWorld San Diego, breaking her own jaw and severing an artery. She died within minutes, blood spurting from her blowhole and staining the water while her year-old calf swam frantically around her.
"This level of aggressive interaction's never been observed in the wild," Rose says.
This violence can be directed against humans.
"Adult males without familes have no social status, no social protection, no social role other than stud," Rose says. In the case of Tilikum, the orca featured in "Blackfish," "his life has been one of unending frustration." Tilikum has killed three people so far.
There's never been a recorded incident of a wild orca killing a human.