Koshima Monkey Habitat

Kojima Monkey Habitat: The Island Where Animal Culture Was Discovered

About 300 meters off the Ishinami Coast of Kushima City in southern Miyazaki Prefecture lies Kojima, a tiny uninhabited island that changed the course of behavioral science. Covered in dense evergreen broadleaf forest and circled by waves of the Pacific, this small island is home to roughly 90 to 100 wild Japanese macaques whose ancestors taught the world a remarkable lesson: that culture is not the exclusive property of human beings. Designated a National Natural Monument in 1934, Kojima is celebrated today as the birthplace of Japanese primatology and as one of the longest continuously studied wildlife populations on the planet.

A Quiet Island With a Loud Legacy

Kojima sits in the East Sea off Ichiki district in Kushima City, separated from the mainland by a narrow channel of shallow water. The island measures about 3.5 kilometers in circumference, covers roughly 32 hectares, and rises to an elevation of around 113 meters at its highest point. Its slopes are blanketed by warm-temperate evergreen forest typical of southern Kyushu, including camphor trees, oaks, and a thick understory of subtropical shrubs.

Despite its modest size, Kojima has become one of the most internationally recognized field sites in the history of animal behavior research. The combination of a closed island habitat, a manageable population of free-ranging monkeys, and unbroken decades of careful observation by Kyoto University researchers has produced a body of knowledge unmatched in primatology.

Why It Was Designated a Natural Monument

The entire island, together with its resident population of Japanese macaques, was designated a National Natural Monument on January 22, 1934 (Showa 9), under Japan's cultural property protection framework. At the time, the designation reflected the rarity of finding a self-contained population of wild Japanese macaques living on such a small offshore island, surrounded by intact natural forest.

Local advocates from the Ichiki community, including residents who had long regarded the monkeys as sacred messengers and called them "Wako-sama," played an important role in securing the protection. After the designation, the island became one of the few places in Japan where researchers could observe a fully wild macaque troop in a stable, bounded environment. This protected status would prove essential when, more than a decade later, the island became the cradle of a new scientific discipline.

The Birthplace of Japanese Primatology

In the spring of 1948, Kyoto University ecologist Kinji Imanishi arrived at the nearby Toi Cape with his student Junichiro Itani to study the semi-wild Misaki horses. Hearing about the wild monkeys of Kojima, the team shifted their focus, sensing that primates would offer a richer window into social behavior than horses could. Their decision marked the beginning of Japanese primatology and, indeed, of modern field-based primate research worldwide.

In 1952, the researchers succeeded in habituating the troop through provisioning—the first such success in Japan. They began identifying every individual monkey by sight, recording lineages, ranks, and relationships in painstaking detail. This combination of provisioning, individual identification, and long-term observation became the methodological foundation of an entire scientific field.

The Sweet Potato Discovery That Astonished the World

In 1953, a local elementary school teacher named Satsue Mito noticed an extraordinary behavior. A young female monkey known as "Imo," about a year and a half old, had begun carrying sandy sweet potatoes to a freshwater stream and washing them before eating. Over the following years the behavior spread through the troop, first among Imo's playmates, then to her mother, and gradually through the wider population. Later, the monkeys began washing potatoes in seawater instead, apparently enjoying the salty flavor it added to their food.

This was the first scientifically documented case of a learned, socially transmitted behavior in a non-human animal—what scientists today recognize as animal culture. The seminal English-language paper on the discovery, published by Masao Kawai in 1965 in the journal Primates, has been cited hundreds of times and remains a cornerstone of the field. Beyond potato washing, Kojima's macaques have also been observed washing wheat grains in seawater (separating sand from grain), entering the sea to swim, and even fishing—behaviors that continue to enrich our understanding of primate intelligence.

Highlights for Visitors

Visiting Etiquette: Respecting a Living Laboratory

Kojima is a protected scientific site, and the rules for visitors reflect that responsibility. Feeding the monkeys is strictly prohibited, as is any physical contact. Visitors should avoid making eye contact with the macaques—they may interpret a direct stare as a challenge—and keep food and shiny objects out of sight. Stepping off the marked beach areas into the forest is not permitted. Following these simple rules helps preserve both the monkeys' welfare and the integrity of decades of behavioral research.

Around Kojima: What Else to See in Southern Miyazaki

Kojima is set within one of the most scenic stretches of Kyushu's eastern coast, and pairing a visit with nearby attractions makes for an unforgettable day. Toi Cape, just south of the island, is famous for its herd of free-ranging Misaki horses, designated as a Natural Monument in their own right. The Nichinan Coast offers dramatic seascapes including Cape Toi's grasslands and the rugged cliffs of Ishinami. Inland, Kushima City features Mochio Garden and several small fishing villages worth exploring. Travelers continuing north can visit Udo Shrine, set into a coastal cave, and Aoshima with its famous "Devil's Washboard" rock formations.