Hunting wild boars is not illegal or punishable by law at some places during certain times across China, although the country is seeking other effective ways to control the rising population of the animal that lacks natural predators.

The National Forestry and Grassland Administration has recently carried out a pilot program to control the population of wild boars through scientific and technological means as well as hunting in 14 provinces. 

The administration has issued a guideline on controlling the wild boars, making clear that in hilly areas in southern China, the density should be kept at two wild boars within one square kilometer, and in northern China, one.

On Nov 12, a wild boar entered a residential building in the downtown area of Nanjing, East China's Jiangsu province, and in April, a wild boar ran on a university campus in Wuhan, Central China's Hubei province.

Such reports of wild boars destroying crops and farmland and entering farmers' houses and causing losses have been heard frequently in recent years, and now the animals are even entering large cities. How did this happen?

The population of wild boars exploded while the ecological environment of wild animal habitats improved a lot after the country took a series of measures to protect forests, nature reserves, according to the administration in an online response to a netizen.

"Wild boars have strong fecundity and high survival rate, especially in southern China where the weather is warm, and food is abundant," said Li Chunwang from the Institute of Zoology at the Chinese Academy of Sciences.

Fewer natural enemies are also one of the reasons for the high survival rate and rapid growth of wild boars, Li said. Wild boar's natural enemies are large predators such as tigers and leopards, but their populations are in slow recovery.

It is not realistic to use the biological control measure by restoring the number of these natural enemies, according to Li.

Many places have turned to hunting to control the animal or shortened the protection period of the animal, according to media reports.

Tongjiang county in Southwest China's Sichuan province plans to hunt 750 from more than 20,000 wild boars within this year. Jinzhai county in East China's Anhui province has also formed a hunting team of 20 farmers to kill the animal.

In July, the Shaanxi forestry authority issued a notice that the period of ban on hunting of wild boars has been reduced from eight months to two, between March 1 and April 30.

However, hunting might not be so effective in China, since the number of hunters has dwindled a lot, and few people have the certificates to have a gun.

"While more people have the awareness of protecting wild animals, the number of hunters have reduced a lot, and hunting needs skills," said Liu Bingwan, an associate professor at the College of Wildlife and Protection Area of the Northeast Forestry University.

Wild boars are fierce, and it is dangerous for villagers to use normal tools such as shovels in the hunt, but it needs a lot of procedures and permits for people to have a gun, a government worker from Shaanxi province said.

It's inefficient to use ropes and clubs, and because there is no economic value of wild boars, people have no enthusiasm for hunting, said Hu Huijian, a researcher from the Institute of Zoology, Guangdong Academy of Sciences.

In order to raise people's enthusiasm, local authorities have explored measures of reimbursements and subsidies. The government of Jinzhai county purchases the meat of wild boars at 20 yuan (3.13) per kilo.

But this way cannot last for a long time, as the subsidies would become a burden on local governments, Hu said.

Apart from hunting, local authorities have also attempted to use other scientific methods.

The national administration has issued documents suggesting the places with losses caused by wild boars to set up electronic fences to fend off the animal and setting up warning signs to remind people to keep a distance.

Field research from his students has shown that when wild boars are hit while jumping over the electric fence, they do not get close, but they do destroy the fenced farmland, Liu said. Such way needs to be reviewed.

Hu said his institute is researching an intelligent warning system that would use infrared cameras to monitor wild boars on real time, and when wild boars are found, it would inform local authorities and nearby villages.

"So far, we have finished the system of identifying wild boars, and are now working on a warning app," Hu said.

The institute is also working on an equipment to drive wild boars after finding them. The equipment will simulate the sound of wild boars being shot and the fake cry after being hit.

"Cases in Fujian province have shown that when wild boars hear the gun shots, they will not visit the place for two to three months, so this equipment can drive wild boars away," Hu said. It can cover an area of up to 1 km.