Talk:M.U.T.O./@comment-5234191-20140516192457/@comment-24868748-20140516204903

Dr. Serizawa tells that the Godzilla species were alpha predators who evolved to the point of feed on radiation. The M.U.T.O.s are parasites who feed on radiation as well, they being "parasites" probabbly absorbed all of the dead Godzilla's radiation, or killed him doing so.

He also states that both Godzilla and M.U.T.O. are natural beings, and since M.U.T.O. was back but thare was nothing on the nature capable of killing them, the planet brought a dormant and ancient Godzilla back to restore the order, or else the M.U.T.O.s would spread throught the planet and kill everything.

Anyway... M.U.T.O. is not a predator, but a parasite who leech energy of the predator. I just think the radiation wasn't enogh to allow them to grow or as they grow, they get killed by the Godzilla species... this is left open in the movie.