The “adaptive fitness” argument seems pretty straighforward.
These are both free-ranging pelagic species with massive ranges.
Orca’s gotta eat, frequently and bigly. If Shamu doesn’t find it here, he’ll go somewhere else soon enough. Because he has to. and can. and will. The Humpbacks, on the other hand, don’t need to eat as regularly. Most of the time they are living off fat reserves. But the Orcas are a problem – they actually can hurt a Humpback, especially any children.
When an orca appears, a humpback’s response seems pretty clear: annoy the hell out of these peksy sea wolves until the interlopers move on. Shouldn’t take long [*]. And it’s probably hella entertaining for a species that appears to have a high play drive
[*] By whale standards. You just know baleen whales groove on Tarkovsky movies.
