They might be lost or lonely or just want to socialize. They might be saying to other deer, the food is great over here, come check it out. Some people say does and young bucks pipe high-pitched grunts, while older bucks utter guttural calls. It s true sometimes. And one day last fall a spike cruised past my stand, grunting like a market hog.
All deer call a little differently, just like people talk differently.
One thing we do know from field research is that a single grunt is short and sweet, lasting a second or less. It sounds like ecc or acc. On stand from the bow opener until the end of gun season, you have nothing to lose by blowing contact grunts. The idea is to contact a buck skulking around in the brush. One day a big deer might like what he hears and come in.