Walking through the forest, you become aware of another presence. For a while there's nothing there but birdsong and the odd drone of a distant plane. But in the occasional silences it becomes evident that something - several things - have been here before you. Every few metres, the earth has been gouged up and pushed aside, the leaves freshly dishevelled.
The animals responsible for all this rearrangement have long gone.
They're nocturnal and nomadic, and their recent notoriety has made them shyer than usual. By day they retreat into the secret parts of the Forest of Dean in southwest England and by night they move from place to place, rooting their way to subterranean treasure and - just as likely - an early grave.
It isn't easy being a wild boar in Britain these days.
Walkers say they live in fear of boars attacking them or their dogs. Farmers complain of damage to crops and fences.
The beaver and the boar were both hunted to extinction in Britain more than 400 years ago but, in the mid-1970s, a few farmers in southern England began importing wild boar from eastern Europe to farm for meat. After a while, some of those boars escaped.
They were joined by boars dumped by illegal importers, set free by animal-rights activists or released by hunters for sport. Separate breeding populations established themselves in Kent and Sussex and the total in Britain is up to 1000.