There goes the neighbourhood

Deer and monkeys invade Japan's high mountains, decimating alpine plants and the birds that live off them

Just below Kita-dake's summit, a snow ptarmigan and her chick were taking a dust bath in the middle of the path. A beady glare from the hen assured me that she had no intention of moving aside; it was for me to walk round the birds. Unthreatened by predators in their high alpine habitat since the last ice age, snow ptarmigan (raicho in Japanese) have little fear of people.

On Japan's second-highest mountain, this was no unusual encounter in the 1990s. It might be now. When Nakamura Hiroshi visited Kita-dake in October 2003, he found none of the friendly birds on a mountainside that once harboured one of the largest colonies in the Japan Alps. Instead, the ground was covered with monkey droppings and deer tracks, something he'd never seen before at this altitude.


Nakamura, a professor at Shinshū University, has been surveying Japanese snow ptarmigan populations since 1981. But it is only in the last five to ten years that monkeys and deer have started to move up beyond the treeline into the alpine zone of creeping pine and alpine shrubs. The implications for snow ptarmigan, which depend on those shrubs for cover and food, are ominous, he believes.

Writing in Yama to Keikoku, Nakamura suggests that Japan's high mountains are being invaded on a broad front. In September 2002, he saw 30 monkeys stuffing themselves on bilberries (kuromame-no-ki) near the top of Otenshō-dake, an almost-3000er in the Northern Alps, Never before had he seen a monkey troop at such a height.

Then in June 2005, he made a traverse between Hijiri-dake and Tekari, two "famous mountains" in the Southern Alps. Deer tracks were seen everywhere along the connecting ridges and all the alpine flowers had been grazed away, except for the poisonous species. The damage was most severe towards the south of the range, between Izaru-ga-dake and Tekari, where all the flower fields (hanabatake) marked on the map had been erased. "And what has already happened in the Southern Alps is only a matter of time in the Northern Alps," warns Nakamura.

The snow ptarmigan are menaced on all sides. Monkeys and deer are cropping their food supply. Kestrels and crows, also newcomers to the mountaintops, are raiding their nests. Foxes are hunting them. Monkeys have been seen stalking the unwary birds; they may have acquired a taste for fresh ptarmigan.

In the past, all these predators and competitors stayed down in the beech and oak woods at the mountain's foot. Dark and inhospitable, the evergreen forests at the middle altitudes kept them from foraging higher up. What has now pushed them beyond their traditional bounds?

Professor Nakamura believes that modern agriculture has caused the population of wild animals to explode. The decline of hunting has also helped numbers to increase. "But it's not the wild animals that have changed their habits," he concludes. "It's that we Japanese have moved from a co-existence with nature to a wholly human-centred way of life."

References

危機に瀕するライチョウ：日本の高山で、今何がおきているのか ("Snow ptarmigan on the brink of disaster – what is happening in Japan's high mountains") article by Professor Nakamura Hiroshi (中村浩志）in Yama to Keikoku, one of Japan's leading mountaineering magazines, January 2007 edition.

Photos of flowers taken on or around Kita-dake between 1991 and 1995; photo of raicho from Natural Monuments of Japan (Kodansha); photo of raicho and yama-skiers by Sunnybeauty

Update

In May 2009, a snow ptarmigan was spotted on Hakusan for the first time in 70 years. The bird became extinct on Hokuriku's highest mountain in the early Showa years. Full report in the Chunichi Shinbun