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Hidakasanmyaku Erimo Tokachi NP, Hokkaido
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Logging in the Saru headwaters began in 1909 to supply Oji Paper’s Tomakomai mill. By 1910, crews used a teppōze—a temporary “gun dam”—to unleash a surge of water and float logs downstream.
This forest is home to Japanese pikas, called Ezo-naki-usagi in Japanese. The Environment Ministry describes these small mammals as glacial relicts, and river-basin records specifically confirm pikas in the headwaters.
Japan designated the Saru River Headwaters Primeval Forest a Natural Monument on December 4, 1970. The official criterion protects a representative area rich in natural features—not just a single celebrated tree.
Sakhalin fir and Ezo spruce grow alongside Erman’s birch here. In autumn, the birch’s changing leaves stand out against the dark conifers—a striking contrast visible from National Route 274.
The “Saru” in the river’s name is thought to come from Ainu sar, meaning “reed bed”—a lowland word for a river that rises among these mountain forests and flows to the Pacific.
