Rare Bird, Returned to Wild, Found to Have Successfully Overwintered; ‘Endangered’ Species May Be Revised to ‘Vulnerable’

By Naoto Suzuki / Yomiuri Shimbun Staff Writer

11:00 JST, May 3, 2025

NAGANO — One of seven artificially hatched Japanese rock ptarmigan chicks was found to have overwintered in the Central Japanese Alps, indicating that an Environment Ministry project to revive the species in the area is making progress, the ministry has announced.

The development is expected to reduce the risk of extinction for the rare wild bird species, which has been designated a special natural treasure by the government and was once thought to be extinct in the mountainous region.

The chicks, including the female one that overwintered, had been artificially hatched in zoos and released into the wild at the Central Japanese Alps in autumn last year, according to the ministry’s announcement in March.

Japanese rock ptarmigan, called “nihon raicho” or “raicho” in Japanese, inhabit only the alpine region of central Honshu. In the 1980s, their number was estimated at 3,000. By the early 2000s, the number had declined to about 1,700, mainly due to such predators as martens and foxes, which invaded the alpine region.

On the ministry’s Red List, the species is classified as “Endangered” with a high risk of extinction in the near future.

The project was prompted by the 2018 discovery of a female Japanese rock ptarmigan on the 2,956-meter-high Mt. Kisokomagatake in the Central Japanese Alps. The bird is believed to have flown from the 3,026-meter-high Mt. Norikura in the Northern Japanese Alps about 40 kilometers away.

It was thought that the species had been gone from the Central Japanese Alps since 1969, with experts believing that the environment had become unsuitable. The 2018 discovery overturned this belief.

The ministry relocated some adults and chicks of the species from Mt. Norikura to Mt. Kisokomagatake and transferred some to zoos to be bred and returned to Mt. Kisokomagatake. The number of the species has now increased to about 130.

The seven chicks returned to the wild in this project originated from birds that had been artificially hatched from eggs collected from Mt. Norikura in 2015 and 2016 and bred for several generations in zoos.

By eating their mother’s feces, the chicks are thought to get intestinal bacteria capable of breaking down the toxins contained in the alpine plants that they eat. However, the artificially hatched chicks lack these bacteria. The problem was solved by feeding the chicks the dried feces of adults in the wild.

In September last year, the seven chicks that had been artificially hatched at zoos in Omachi, Nagano Prefecture, and other places were released near the summit of Mt. Kisokomagatake. Four of them were found to be alive at the end of October.

On March 26, the ministry announced that one of the four chicks had survived the winter and that it was eating alpine plants and always with a male that was not one of the released chicks.

It is hoped that the couple’s chicks will hatch from spring through summer.

“If this project succeeds, we will have established a technology to prevent extinction,” said Shinshu University Prof. Emeritus Hiroshi Nakamura, an expert in avian ecology who has been leading the project. “By breeding the species in zoos, our long-held dream [of reviving the species in the Central Japanese Alps] is about to be realized.”

The ministry will continue to study the species’ condition and, depending on the results, consider lowering its Red List category by one level to “Vulnerable” in fiscal 2029 at the earliest.