Is a mastodon dinosaur a predator?

Okay, let's back up a bit. Mastodons were built like elephants, whit the tusks and trunks and hair and the whole tamale. Being mammals, and not reptiles, they were barely related to the dinosaurs at all. They didn't even evolve until 64 million years after the dinosaurs went extinct.

Back to your question, they were herbivores, with teeth more built for grinding plant materials than tearing meat.