The tunnel isn't long, but it is narrow. If they dig through into the squishy mushrooms and fungi, they'll discover a sharp crystal hidden underneath that can be broken off with enough effort. They may find that the secretions from the fungi will cause some mild skin irritation. The mushrooms, however, are edible if they're capable of recognizing common mushrooms, but they'll need to use their limited water to wash off the same sticky secretions that's touched the mushrooms.