Badger fur is very bristly and grows over a rough, loosely fitting skin. A characteristic of the badger is that their colouring is the other way around to normal mammal colouring: the back is lighter than the belly. Badgers live in family groups in setts which they occupy for almost their whole lives and which are sometimes used by successive generations. This is why these burrows are often complex structures, dividing repeatedly with many chambers, a labyrinth of passageways and several exits. Not all of these are used at the same time. These passageways can extend up to 5 m underground. The entrances to this subterranean system are often protected only by a bush and are difficult to spot.