BIOSPHOTO/Alamy
Lance Kennedy
Kaiwaka, New Zealand
In my opinion, none of the replies thus far has actually answered the question. Note that orcas aren’t the only ones that don’t attack and eat humans. Despite the phrase “man-eating shark”, cases of sharks killing and eating humans are vanishingly rare. Typically, up to 10 people are killed by shark attacks each year, but the bodies are very often recovered – with nasty injuries, but uneaten.
My hypothesis on why they aren’t eaten is due to the large number of poisonous animals in the ocean. For example, if an orca or a shark decided to make a meal of a large, fat, juicy moray eel, that would result in a very sick predator, due to the toxins inside the flesh of the moray.
So it makes sense that marine predators should evolve an aversion to eating the flesh of those species they aren’t familiar with. Each orca population seems to have a “shopping list” of prey animals its members know are safe to eat. Here in New Zealand, orcas are big on killing and eating stingrays. In other places, it may be salmon, seals or some other prey, but all of them are known to be safe to eat.
To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
Â鶹´«Ã½ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
