Whales in the southern oceans
have similarly wide-ranging effects.
One of the many post-rational excuses
made by the Japanese government for killing whales
is that they said, "Well, the number of fish and krill will rise
and then there'll be more for people to eat."
Well, it's a stupid excuse, but it sort of
kind of makes sense, doesn't it,
because you'd think that whales eat huge amounts
of fish and krill, so obviously take the whales away,
there'll be more fish and krill.
But the opposite happened.
You take the whales away,
and the number of krill collapses.
Why would that possibly have happened?
Well, it now turns out that the whales are crucial
to sustaining that entire ecosystem,
and one of the reasons for this
is that they often feed at depth
and then they come up to the surface and produce
what biologists politely call large fecal plumes,