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Conservation society introduces unique method to curb ballooning deer population

A Japanese deer appears to lick salt left for them in Minakami, Gunma Prefecture, in July 2017. (Photo courtesy of the Nature Conservation Society of Japan)

MINAKAMI, Gunma -- Extermination efforts by the Nature Conservation Society of Japan to prevent an increase in the number of Japanese deer began in the Akaya forest here at the beginning of November, and the society hopes their unique methods will help regions control deer populations nationwide.

After studying the habits of the deer, the society came up with these rules: When a gathering of three or fewer deer is encountered, all of them will be exterminated, while groups of four or more will be left alone. This method was established so that areas with a low concentration of deer can be managed before their numbers grow out of hand.

The habitat of the Japanese deer has expanded due to decreases in the population of hunters and less accumulated snow. According to an estimate by the Ministry of the Environment, there were some 3.15 million deer in Honshu and southward in fiscal 2014 -- over 10 times more than the roughly 290,000 estimated in fiscal 1989. The agricultural damage carried out by these deer has grown to about 6.5 billion yen, with somewhere around 7,000 hectares of forest reportedly taking a hit.

With regions shouldering the most losses making progress with extermination efforts, the deer population had dropped to roughly 3.04 million by the end of the 2015 fiscal year. However, extermination to prevent damage before it occurs in areas where the deer population is still sparse is difficult, and has become an issue.

So far, no heavy damage from deer has been confirmed in the some 10,000-hectare Akaya forest. But signs of their presence, such as deer being caught on automated forest cameras, have increased 8.5 times in eight years, pointing to an overall trend toward population growth.

That's why the nature conservation society has placed deer treating salt in locations where high concentrations of the animals have been confirmed. If a group of three or less of the creatures gathers at the salt lick, they are all exterminated. However, in the case of a hard-to-handle group of four or more deer, they are left alone. The policy takes into account that in the cases of large groups, those animals that manage to escape become more cautious and harder to catch, and aims to properly manage the population keeping the habits of the creatures in mind.

According to the society, efforts to exterminate deer in overpopulated areas are being carried out throughout Japan, but this is the first project to take on population growth at the prevention stage.

"Response to damage done by deer is often too late, and the measures come with an enormous price tag," said professor Koichi Kaji of the Graduate School of Tokyo University of Agriculture and Technology. "If low concentrations of deer populations can be maintained, the diversity of the ecosystem can also be protected."

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