Mice can do nothing on their own until a Shaman arrives to help.
There are two shamans on this level each with their own color hole. The shamans may engage in a shaman battle or call a truce and race to be the first the build. Note that the platforms on this level extend past the edges of the screen. Therefore, it is harder than normal to cannon ball the other shaman off the map. A quick solution is to simply kill the other shaman and summon a globally anchored large plank above the gap between the mice and your hole.
The blue shaman has a seemingly slight advantage on this map, as the pink shaman must go farther to bridge to their own hole. After arriving at the bottom of the map, the blue shaman must simply build a bridge for the mice to cross.
The pink shaman, despite being unable to stand near their hole, actually has an advantage since the blue shaman must run farther to be anywhere near their hole. The pink shaman may simply stand above the left gap and build a hanging platform bridge, or simply place a red anchored large plank above the left gap. To reach their hole, the pink shaman must block the blue hole before bridging to the center, and then to their own hole.