A wild boar runs through the grounds of a Kyoto University dormitory in the western Japan city of Kyoto - 2017 Kyodo News

Less than 20 years ago, the only challenges for the 100 residents of the tiny island of Kakara, off southwest Japan, were the elements and ensuring the fishermen’s catch could get to market on time.

Today, the islanders are outnumbered three to one by wild boar who feast on their gardens and are becoming increasingly aggressive and territorial.

The problems facing the residents of Kakara are being repeated across Japan, with boar numbers exploding as rural populations decline.

Japan's rapidly ageing and shrinking population is part of the reason behind the increase in wild boar, as older rural populations die out, leaving towns and villages empty. Meanwhile, young people are also moving to the cities in search of work. The number of people with shotgun licenses has also fallen sharply in recent years.

And as the people leave, the boar are moving in.

The first boars apparently swam to Kakara, which covers a mere 1 square mile and sits between Fukuoka and Saga prefectures, but have been in hog heaven ever since.

They have found a place with no natural predators and plenty of crops, such as pumpkins and sweet potatoes, that the local people grow in their back gardens.

Other than farming and fishing, the island’s only other industries were small-scale tourism and growing camellia for use in cosmetics, Kyodo News reported, but the famously aggressive boar have chased the tourists away and eaten the camellia plants.

Local children cannot play outdoors for fear of being attacked and residents have stopped walking even relatively short distances for fear of encountering one of the aggressive creatures.

Desperate islanders have set countless traps and catch around 50 of their tormentors every year, but that figure is far outstripped by the rapidly breeding boar population – a sow can give birth to as many as six piglets a years.

Some residents are even suggesting that they should evacuate the island, abandoning it to the wild pigs. Across Japan, confrontations between boar and man are inevitable as the hog population rises, and rural media are frequently reporting incidents in which humans have come face-to-face with large beasts.

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In October, a large specimen barrelled into a suburban shopping mall on the island of Shikoku, biting five staff and causing mayhem before it was captured.

In December, two boars managed to get into a high school in Kyoto and panicked students had to be evacuated.

Elsewhere, they are finding their way out of the forests and fields and into train stations, gardens and school sports grounds.

And with few checks on the boars’ territory, they are growing larger as well as more numerous.

In February, farmers in north-east Japan caught a male that weighed in at 280 pounds, well over the average 220 pounds of boars in Europe.

They are also expanding their range into areas that were previously considered too inhospitable, taking over villages with shrinking populations.

They are being given even greater licence to roam in areas close to the Fukushima Dai-ichi nuclear plant, abandoned in March 2011 in the aftermath of the destruction of three of the plant’s reactors and the release of radiation across the surrounding countryside.

Local people fled to safety; the wildlife remained and thrived.