Simian stories: Japan’s monkey queen topples alpha to emerge omega

The macaque, named Yakei, presides over a troop of 677 monkeys in Takasakiyama Natural Zoological Garden, which was established as a reserve for monkeys in 1952. There are two troops on the island reserve, and they spend most of their time roaming the forested mountain at its center. They also make daily visits to a park at the base of the mountain, where the staff provides food. Since the reserve opened, its staff has kept tabs on the romantic and political struggles of its simian residents. Yakei’s ascent to alpha status surprised both scientists and reserve workers, who are now closely observing Yakei’s reign to see how long she can maintain her supremacy. The Japanese macaque, also known as the snow monkey, is a highly intelligent species native to Japan. It is well known for its beet-red bottom and affinity for soaking in hot springs. While many animals, including bees, hyenas and elephants, live in female-led societies, a hostile takeover by a female “is very rare in Japanese macaque society, and only a few cases have been reported in the history of primatology,” Yu Kaigaishi, a research fellow at the Japan Society for the Promotion of Science, said in an email.

Japanese macaque society is based on a strict hierarchy. The higher an individual monkey’s rank, the greater its access to food, mates and resting locations. Females inherit the rank just below their mothers and rarely leave the troop they were born into. Males leave their natal troop upon reaching puberty and join a new troop, where their rank is usually determined by the amount of time they have spent in the troop. However, rank is sometimes gained through acts of violence, typically male on male. Yakei confounded what primatologists expected among Japanese macaques. Last April, she beat up her own mother to claim the top spot among the females of her troop. While most females would be content there, Yakei continued to fight.

According to reserve workers, Yakei assaulted three high-ranking males, then came after Nanchu, who had led the troop for five years. At the age of 31, Nanchu is elderly for a Japanese macaque and was ultimately no match for the young and determined Yakei. “She physically attacked and defeated Nanchu, consequently acquiring the highest ranking in the troop,” said Kaigaishi, who studies the behavior of Japanese macaques.

After Yakei’s altercation with Nanchu, reserve workers performed what is known as a “peanut test”: providing the monkeys with peanuts and seeing who eats first. Males and females stepped aside to let Yakei eat first, a confirmation of her alpha status.

Since then, “Yakei has shown some behaviours typically seen only in dominant males, such as walking with her tail up and shaking tree branches with her body. It sounds as if she is behaving like an adult male, being more aggressive than other individuals,” said Kaigaishi, who is not affiliated with the reserve. If Yakei’s rule continues, scientists like Kaigaishi will have a unique opportunity to study how Japanese macaques fare in a society led by a female. “Japanese macaque society is so dramatic and unpredictable,” he said, “which is why many people, both researchers and non-researchers, love to observe them.” Roth is a reporter with NYT©2022

The New York Times