Ants are probably the least of the critters that inhabit compost piles. If you were to check closely you'd discover all kinds of creepy crawlers. Really, though, that's a sign of a healthy compost. We have huge ones here in the western U.S. called silage pits. Corn stalks and other material are put into shallow pits, covered with black plastic and then, during winter months the silage is fed to live stock. When the pit is uncovered for feeding, you'd be amazed at the insect population. the cow's love it though!