Terrestrial crayfish usually roll the mud up in little balls and construct a short chimney(but not always) above their hole. I have seen turtles attempting to nest that dig holes similar to those you picture. It would be unusual to see a hundred of them though. The female slider sometimes will try a few times before she settles on what she likes and finally lays her eggs. I think that it is a natural attempt to fool nest robbers ( coons, coyotes, skunks, etc) by leaving many false areas to confuse them.
Tom Sterling (Shelby County )
