The killer whales that feed on mackerel have been found to have very worn down teeth as a result of their feeding behaviour.

BBC: Earth News - Massive killer whale pod sighted

It can even be an exorcism of sorts, feeding photos of former lovers or ridiculously large medical bills into the metal teeth, one piece at a time.

WSJ: Paper Shredders: Finding Shredded Bliss

The animal's pointed, serrated teeth and large gaping jaw meant it would have been suited to feeding on large-bodied prey.

BBC: Tyrannoneustes lythrodectikos