European badgers dig several categories of sett, from small outlying holes to a main sett that anchors a group's territory. Main setts can hold tens of entrances and tunnel networks measured in hundreds of metres, arranged over several levels with chambers for sleeping and breeding. Because the digging is cumulative, the structure is the product of many badger lifetimes.
Some setts have documented occupation running to a century or more, and archaeological evidence shows badgers reusing the same sites over far longer spans. The animals bed chambers with dry grass, bracken and leaves and periodically drag the old bedding out, a reliable field sign of an active sett.
Badgers are social in a way most mustelids are not, living in groups that share a sett and a territory while often foraging alone. In much of Britain and northwest Europe, earthworms make up the largest single part of the diet, which ties foraging to soft, damp ground and makes dry summers hard on them. The badger's role in transmitting bovine tuberculosis to cattle in Britain and Ireland is genuinely disputed, in magnitude and in what follows for policy.