Japan’s master of suspense helps save small forest animals

Above a road through a forest hangs a long, thin suspension bridge resembling a power line. Japanese dormice, small field mice and squirrels — forest-dwelling species that are recognized as national natural monuments — scramble along it as if it were just another tree branch.

Koichi Otake, 66, of Nerima Ward, Tokyo, who was previously an engineer for leading general contractor Taisei Corp., is promoting a project for the construction of these suspension bridges, which are to be used by small animals inhabiting forests that have been split by development.

“They’re just as cute as could be. I fell in love with dormice,” Otake said with a sheepish grin. The dormouse is a rodent about 10 centimeters long and weighing around 20 grams. It spends half of the year hibernating, and its adorable curled-up sleeping posture earned it the “round mouse” sobriquet.

Otake’s work at Taisei included geological surveys for the construction of dams and tunnels and technological development for road foundations. His first encounter with the dormouse came after he attended a work-related lecture by a researcher in small-animal protection.

When forests are cut to build roads, small animals like the dormouse find their environment reduced. If they try to cross roads, they frequently end up being hit by a car. When he learned about this, Otake thought that because his work involved the building of roads, “I should do something to keep the animals from being harmed,” he said.

Before 2007, the only elevated pathway for small forest animals was located in the Kiyosato Kogen highland in Yamanashi Prefecture. However, it cost ?20 million to build. That year, Otake began putting his technical knowledge to good use and, after several trial-and-error attempts together with other construction engineers, hung a bridge measuring seven meters high, 25 centimeters wide and 13 meters long above a city road in the same Kiyosato Kogen highland. By making the structure as simple as possible, they were able to keep construction costs at around ?2 million — a figure within the range of even a small construction company.

The project started out as an extension of his work at Taisei, but after watching the videos taken to verify the use of the bridge by small animals, Otake became keen to spread their use more widely. In May 2012, when he was 63 and had one year to go until he would be ineligible for mandatory reemployment after retirement, Otake founded the Animal-Pathway & Wildlife Association along with other researchers and engineers.

The main work of the association is to spread the use of these pathways through such means as small-animal damage surveys and lectures. Nationwide, a total of 40,000 to 50,000 pathways are thought to be needed, but only five currently exist, located in Yamanashi, Aichi and Tochigi prefectures. The association’s operating costs are met by donations, grants and consulting fees from companies and individuals, but outlays are also high.

Nevertheless, the association maintains it plans to be active in the long term, and firmly believes that because roads are used by everyone, it is important that the project be carried forward.

Infrastructure-enhancement works, such as road network maintenance, make our life convenient, but they also negatively impact the environment. An increasing number of companies are recognizing their responsibility as users of the natural world and are becoming involved in environmental conservation.

Obayashi Corp., a leading general contractor, obtained permission from the Forestry Agency to manage forests and works to maintain the ecosystem by cutting undergrowth and thinning forests to maintain proper spacing between trees.

At Taisei, where Otake worked, employees and their families devote time to building nesting boxes for Japanese dormice. The completed nesting boxes will be used in ecology studies in Yamanashi, Hyogo, Shimane and other prefectures.