Our new mouse cage setup. The two new cages are on the right, while the two cages we bought two weeks ago are on the left.
To hold the new setup we assembled two of our IKEA modular shelf systems in our living room, which will also give us much-needed storage space. We simply attached the two new cages to the two old cages (while the mice were still in them), and let the mice discover the new cages on their own. It didn't take long before Rem, Deuce, and Ace all found the new cages, and were happily exploring.
Ace (or maybe Deuce) looking into the new cage.
The mice all displayed nearly identical exploring behaviors at first. They crawled through the tube leading into a new cage, sniffed the new cage's interior (and maybe put down a paw or two), then turned around and rushed back to the familiar cage. Then they turned right around and walked back through the tube and into the new cage without looking back. It didn't take the mice long to learn how to get around the entire setup.
Ace exploring one of the shelves of our new CritterTrail Three.
Right now the mice are running all over the tall cage, and are having a blast. The new red wheel is a huge hit (they now have three wheels total), and they can't seem to get enough of climbing on the bars.