A study in the Marine Mammal Science journal examines the question of why Southern Resident orcas in the Pacific Northwest harass and sometimes kill porpoises without eating them.
Such behaviour has been passed down through the generations and across social groupings, and has been recorded as far back as 1962.
The question of why comes to mind.
Not on the menu
Certainly not to eat them. Southern Resident orcas do not harass the porpoises to consume them.