psualt is correct, skunks are out feeding on white grubs right now, as are raccoons and many ohter animals incl. black bears. You can smell a skunk, typically far ahead of the danger but not always. A raccoon has no smell that gives it away so you could trip over one if it is obstinate or feeding. They love grubs like candy. Grubs are full of protein now and very tasty, to a skunk. So.....a growling could be animals competing for feeding areas, female animals although its a bit early for breeding season or just about anything else.
I remember a story of a raccoon as a pet. The guy would put a candy bar in a buttoned pocket and then put the raccoon on his shoulder. The raccoon would climb down his arm/chest to the pocket, delicately unbotton the pocket, remove the candy bar and open it carefuly, then consume it happily. The little hands/digits are so delicate and they use them so deftly it is amazing to watch up close. We had a mother birth them in a window well under our deck so we had a yearly raccoon terrarium under our deck. Got to watch the grow up (they did so quickly) then venture cautiously into the yard at dusk the first few nights. After that they ran out like children would and right to the mulberry tree to engorge themsleves on the berries, purple poop the next day. Very cute little animals. They never bothered our gargage can or any property.