What was that sound?

Yesterday, I was out checking fences in the north pasture. The deer reek havoc on the electric fence over the winter and this year was no exception. It's a near do-over.
Walking the fenceline was a mucky and snowy experience, so I decided to walk back in the middle of the pasture where the snow had melted. As I walked, I could hear a strange sound. The best way to describe it would be the sound that ice makes when you walk across it and you can hear millions of tiny cracks forming. Now multiply that sound by an exponential power and you have the sound I was hearing. I stopped walking to listen and the sound was still there, so it wasn't my shoes in the wet earth. I listened for a few minutes because the sound was very mesmerizing. After a bit, the sound began to subside.
I began to walk again and the sound picked up. So, I stopped and it went down again. I did this several times. The sound was not just where I was walking, it went out through the whole pasture.
What was that sound?
Hint, there were also tiny piles of wet dirt all over the place.
Give up? The sound was the nightcrawlers. They were coming up to the surface now that the top layers are melted. As I walked, I disturbed them and they were slipping back into the earth with millions of tiny sucking sounds.
This earth is amazing!