We live in an area with similar wild animals and it's only the squirrels and a few birds that ever bother with the compost. We have a 4 sided pallet bin. Twice in 12 years it's been thrown apart by a bear. The palllets were not damaged, DH just tied them together again. It was interesting to see the big bear paw print in the finished compost! I've never seen a crow or raven or any other animal near it. I've recently put a pile of fine wood shavings beside the bin to scatter over each layer but that's because I hope to get faster decomposition. It will I expect also change the odor of the bin so you might think about using sawdust, shredded paper or shredded leaves to do the same.

We have the creek, but when we are in drought, portions of it go dry, so I have two birdbaths, a small fountain out of galvanized tin, and bowls of water for cats, strays and mine. Has anyone else noticed that mosquitoes don't seem to lay eggs in galvanized tin? There are never any larvae in the fountain or in a small galvanized tub which is painted red. At first, I thought it might be the red color they didn't like, but then noticed there were never any in the fountain either. I also feed a stray tomcat that is deaf and blind. He sees light and dark but that's it. I also have a possum and raccoons that steal cat food whenever they can. I didn't know it, but the possum was living under a huge piece of cardboard that I keep to block weed killer when I'm spraying. When I discovered him, I chased him out of the garage with a broom. He got about five feet out in the driveway and seemed to realize, wait a minute, I live here! Then he turned around and came running and hissing at me. Let's just say I'm glad there were no witnesses to my retreat. It involved screaming and running. DH finally chased him out. I would adore some hedgehogs. They are one of the cutest things I've ever seen.

We get holes in the yard, too, and sometime get curious enough to try filling them up like you did. And like you experienced, they never do. Hopefully if there was a snake in there, the flood encouraged him/her to go out another hole and never come back. Probably not but clinging to this thought allows me to get to sleep. I don't really care who/what dug a hole, as long as there are no snakes in it! This may help you discover why there's a hole in your yard: what dug this hole?

sorry three responses haha... didn't see the bottom two pictures. Apparently the scroll feature is not over-rated. Thanks for posting this, I am not 100% confident on what the predator is and wish I had the opportunity to see it in person. My best guess is a weasel... I don't know where you are from but I'm assuming least weasel to be able to fit into the vole's burrow. Weasels have an innate instinct to kill as much prey as possible if the opportunity arises. The reason they do this is because they have a high metabolism and take the protein as they can. If they have excess food they will sometimes only eat the brains or in most cases they will store the food for a later time. Fishers also make food caches and a few others in the weasel family. I believe this picture shows a weasel's "cache." I don't think the weasel will come back and finish off the vole family because i'm sure some bird or insect will get at them first (especially because it seems like you live in a pretty warm area). Still... it may... Pretty awesome find and it seems like you found a natural pest control! no more trapping!