Drivers in Hokkaido have been advised to take extra care due to a spate of incidents in which Yezo sika deer have bolted onto the roads of Japan's northernmost prefecture and caused serious traffic accidents that have resulted in injuries and deaths.

The number of road accidents involving deer has been rising steadily in the prefecture, reaching a record high for the seventh consecutive year in 2023 of 5,287, including two deaths.

Experts blame reduced snowfall caused by global warming which has allowed the deer to expand their range from the eastern part of Hokkaido to the central and western parts where more people live.

According to Hokkaido prefectural police, the number of traffic accidents involving deer has been trending upwards since 2016. In 2023, there was a 2.9-fold increase from a decade earlier.

Seven people died and 26 were injured in deer accidents that occurred between 2019 and 2023.

File photo taken in October 2022 shows a minivan that was involved in a head-on collision with a truck after hitting a deer in Shibecha, Hokkaido. (Kyodo)

On the afternoon of Oct. 26, 2022, for example, a minivan collided head-on with a truck in the opposite lane on National Route 272 in the town of Shibecha, eastern Hokkaido, after the van hit a deer that had darted onto the road.

Two men in the van were killed and the male truck driver was seriously injured. A large doe was found dead at the scene.

Traffic accidents involving Hokkaido deer mainly occur during their mating period between October and November, with dusk the time of the day many encounters happen on the road.

In 2023, the most accidents -- 387 -- occurred in the central Hokkaido city of Tomakomai, followed by 281 in Kushiro in the eastern part of the island.

Yezo sika deer were endangered during the Meiji era (1868-1912), according to the Hokkaido prefectural government's wildlife division. But their numbers began to grow in the 1980s, partly as a result of hunting restrictions.

The estimated deer population in Hokkaido, excluding the areas under supervision of the Shiribeshi, Hiyama and Oshima subprefectural governments in the western part of the island, was 720,000 in fiscal 2022, up 1.8 times from fiscal 2000. The population is also increasing in the three subprefectures.

Recently, the Hokkaido deer population has expanded westward due to years of relatively low snowfall along the Sea of Japan which has made it easier for the animals to winter away from their traditional habitat. Experts say the increase in their numbers in heavily trafficked areas is an obvious factor in the increase in accidents.

Controlling the deer population is easier said than done. In the 1970s, there were about 20,000 hunters, but now there are only about 6,000 largely aging locals willing to participate.

Although the Hokkaido government provides training programs to improve young hunters' skills, it remains to be seen whether or not there will be any significant progress in culling the deer population.

Traffic accidents involving deer have also become a big headache for insurance companies.

In October and November last year, there were 1,085 cases of insurance payouts totaling 670 million yen ($4.5 million), all-time highs in both categories. Insurance payouts quadrupled from a decade earlier.

The Hokkaido branch of the General Insurance Association of Japan has printed posters and handouts for distribution to drivers at roadside rest stations, rent-a-car offices and other places, reminding drivers to be wary of the animals.

The notices point out that "if you see a deer, there likely are more nearby," also explaining that "deer often bolt onto the road" and they "react by stopping in headlights."

"Even if people think an area is deserted, we hope they drive slowly and carefully because deer suddenly run out of the woods," said Toru Nagasaki, secretary-general at the branch.

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