Every day, I re-fill clay cavern with seeds, but for the last few days, I have found one of the entrance tunnels full of gravel and seeds;completely filled so nothing could get through! I have back-filled the space around clay cavern and the box it is in with gravel, as the mice and voles kept climbing out of the cavern and hiding in-between it and the outside of the box. This mouse often jumps up, through a small hole at the top, retrieves gravel and then brings it into the chamber and packs it in the tunnel. Sometimes bits of gravel fall in, past the camera and he uses those, combined with seeds. I would imagine that this is quite common behaviour… if you have collected a stash of food, then you don’t want any other animals to find it, so you would block up any holes that might allow something else to get in. It is fascinating behaviour and even nicer to have caught it on video!