Do you see the area of grass that is not completely covered in dead hazel leaves, that runs from bottom left of the photo to the lime green patch of moss top right? That's a small mammal trail, made by a hedgehog or a squirrel running from the pile of prunings out of the picture to the left, up to the hazel tree on the right.
This one is quite wide and made by a big enough animal that you can see that the grass is slightly depressed by the mainly nocturnal traffic. If the light and weather conditions are right, you can stand in the spot this photograph was taken and see a series of tiny trails through the grass. The smaller ones are made by voles, shrews and mice, crossing the orchard on their nightly quest for food.