I have a group of 4 mice who live together in a very large tank. They have been very happy with this wooden house that they fill with torn up tp and then bank up the sides with the substrate on the outside. Today when I looked in this morning they have moved all the nest from the wooden box to the opposite side of the tank. Why would they do that. They have lived in this tank for 3 months. They have had various 'houses' as eventually I chuck them because they've either chewed them to bits or they stink. Point being they like being at the other side of the tank because I put paper over that end to make it darker for them. They've took all the paper from inside the house and are nesting in the open. Any clues what this is about ?