Ezo Nakiusagi
The Ezo nakiusagi, or Ezo pika, is a subspecies of the northern pika, a small mammal closely related to rabbits and hares. Pikas are found in northern regions of the Eurasian continent and there are approximately 30 species worldwide.
The Ezo pika is about the size of a human fist and weighs around 120 grams. It lives on rocky mountain slopes and feeds on flowers, moss, and other plants.
In summer, it forages and stores food. In winter, it lives off its gathered reserves and shelters in spaces between the rocks, but it does not hibernate.
The map shows the habitats of the Ezo nakiusagi. These include rocky mountain slopes and outcrops where alpine plants grow. The habitats are spread throughout the Shikaribetsu area.
The Ezo pika is endemic to Hokkaido and is found only in the mountains of Central Hokkaido, typically at high elevations. However, the species can also be found on rocky mountain slopes at lower elevations provided there are alpine plants to feed on.
These small creatures make high-pitched squeaks—a characteristic reflected in their Japanese name: nakiusagi means “squeaking rabbit.”
Northern pikas arrived in Hokkaido during a previous ice age.
Around 20,000 years ago, Earth experienced temperatures much lower than those of modern times. During this period, the temperature in Hokkaido was up to 10 degrees Celsius lower than current temperatures.
More of Earth’s water was ice, and the sea level was as much as 120 meters lower than today. Lower sea levels exposed shallow seafloors, and these became land bridges that connected islands and continents.
Hokkaido was connected to the Eurasian continent via Sakhalin. Many animals, including mammoths, migrated to Hokkaido via this land bridge.
The northern pika is also believed to have come to Hokkaido in this way, although they may have migrated during an earlier glacial period. When they came to Hokkaido, forestland would have been scarce and much of the terrain would have been rocky. This is thought to have facilitated the pika’s migration.
The Ezo pika is only found in certain areas of Hokkaido, such as the Taisetsuzan and Hidaka mountain ranges in the central part of the prefecture.
They are not found in Shiretoko, in northeastern Hokkaido, or Akan, in eastern Hokkaido, despite these areas having seemingly ideal mountainous habitats. The type of terrain linking these areas and the effects of volcanic activity, such as the distribution of hot springs, are thought to have impeded the northern pika’s migration.
The northern pika’s migration to Hokkaido would have been a gradual process that occurred over tens of thousands of years, ending when the temperature rose around 10,000 years ago.
This temperature change encouraged the growth of forests at lower elevations, and the Ezo pika moved higher into the mountains.
Gradually the habitat of the northern pika became limited to a few high mountains where rocky terrain remained.
In the mountains of Shikaribetsu, permafrost and features known as “windholes” create an environment that supports cold-climate plants and animals such as the Ezo pika. There, visitors can envision what Hokkaido might have been like during the last ice age.
