I once asked a professor of agriculture in the southwestern United States what sort of fence would keep a goat from escaping.

"Well," he replied, taking a long and pensive draw on his cigarette. "If it can keep out air and keep out water, it can keep in a goat."

Those wise words came to mind early one recent Sunday morning as I stood near a steep, wooded ravine a few hundred meters from my house in rural Nagano Prefecture. Across the head of the ravine, which cuts down from the forest through farmland below, stands a two-meter-high wire fence topped with four rows of electrified wire intended to keep undesirable wildlife out of the village.