Aydin Orstan of the Snails’ Tails blog was incensed to read this part of a sentence from an article in The Journal of Molluscan Studies: “…lived there for an extensive period, predating the pinninds’ mantle.” What the authors meant to convey, says Dr Orstan, was that the carnivorous Cymatium specimens recovered from inside the mantle cavities of several species of bivalves had been preying on the latters’ mantle tissue. He also points out that in three subsequent sentences of the article, snails are stated to be “predating on” bivalves.
‘Predate’ is the verb meaning “to happen before”. Hence, if one is writing about prey and predators, one needs to be clear about what is meant in English, by using a term such as “were preying on” as Dr Orstan suggests.
‘Predator’ and ‘predation’ are nouns that do not have a verb form in common English usage. A literal reading of the passage identified by Dr Orstan is that the snails lived before the bivalves.
A commenter at the Snails’ Tails post writes that he uses the term “depredate”, but I don’t think this is necessary or desirable, or even correct in this context (to my knowledge and my dictionary’s).