When it comes to the animal kingdom, anything goes, it seems. From sounds heard miles away to spontaneous sex changes, these little-known facts were probably not discussed in that high school biology class you took.
That's how you call up pigs in my neck of the woods. When they reply, you can hear their squeals before you see them coming. The mud lovers can squeal louder than a jet engine's roar, causing many a farmer to lose his hearing over the years.