Deer Population Surges in Southern Alps

A herd of approximately 200 to 300 deer has been captured on camera in the Southern Alps, signaling a rapidly growing population that is causing significant damage to mountain ecosystems. Footage from August 1 shows the deer covering the ground near Futagoyama, near the Southern Alps National Park, which spans Nagano, Yamanashi and Shizuoka prefectures.

Tatsumi Kawasaki, a mechanic for Toho Air Service, spotted the herd and initially thought the grass was a different color. However, upon closer inspection, he realized they were deer. Shinobu Saito, manager of the Umanose Hut in the Southern Alps, had never seen such a large group of deer together and expressed astonishment at their numbers.

Wild deer typically live for six to seven years, and their population growth is driven by their high reproductive capacity. Takayoshi Yamauchi, an associate professor at Iwate University, explained that deer can continue producing offspring quickly as long as there is sufficient food. Previous observations in the area have shown large herds, but this current population is unprecedented.

The expanding deer population is causing severe damage to alpine vegetation, which in turn poses risks for people and infrastructure. Saito noted that the deer have been eating plants like the Japanese globeflower, a flowering species found in the mountains. The deer's feeding habits can also create conditions that lead to landslides, as exposed soil becomes susceptible to water flow during heavy rainfall.

Damage from deer has been reported across Japan, including in Anji Kamo Shrine in Himeji, Hyogo Prefecture, where deer have been eating hydrangeas for about a decade. In Koriyama, Fukushima Prefecture, a field expected to produce sunflowers for an annual festival was almost completely destroyed by the deer. The festival was ultimately canceled due to the extensive damage.

Deer are also creating traffic hazards, with collisions involving deer occurring in urban areas in Sapporo, Hokkaido, in 2025. Across Hokkaido, the number of traffic accidents involving Ezo deer has reached a record 6,705 cases in 2025. In the Kanto region, Reeves s muntjac, known in Japan as kyon, have expanded rapidly, with their population estimated at 94,100 across 18 cities and towns.

Experts warn that the ecological consequences of the deer population can be more severe than those caused by bears. Yamauchi explained that when there are large numbers of deer, they can consume all of the vegetation covering the forest floor, creating concerns about landslides and other disaster-prevention risks. Frequent heavy rainfall has also exacerbated the problem, leading to muddy torrents resembling flash floods that flow down from mountain areas after intense rain.

The declining and aging population of hunters, coupled with climate change, is making it increasingly difficult to control the deer population through hunting. Yamauchi believes that the number of hunters has fallen substantially, and the remaining hunting population is aging, further complicating efforts to manage the deer population.

Factors such as declining snowfall due to warmer temperatures and expanding habitats due to milder winters are allowing deer to venture into higher elevations, previously uninhabited by them. This ecological imbalance poses a significant threat to Japan's mountain ecosystems and highlights the urgent need for effective management strategies to address the growing deer population.