The reign of Japan’s monkey queen has just begun.
Last year, Yakei, a 9-year-old female Japanese macaque, fought several other macaques, including her own mother, to become the alpha of her troop. That made Yakei the first known female troop leader in the history of Takasakiyama Natural Zoological Garden in Southern Japan, which was established in 1952 and is home to over 1,000 macaques.
But during her first breeding season as queen, which began in November 2021 and concluded in March 2022, a messy love triangle threatened to weaken her grip on power. According to officials at the park, the macaque that Yakei showed interest in mating with, a 15-year-old male named Goro, rejected her advances despite their coupling during a previous breeding season. Meanwhile, an 18-year-old macaque named Luffy did his best to woo Yakei, much to her displeasure.
Japanese macaques are polyamorous and scientists were worried that Yakei would not be able to maintain her status while pursuing and rejecting potential mates. Tensions run high during breeding season, and a challenge from a spurned male could easily rob Yakei, an average-sized female, of her rank. Yakei rose to power by defeating her troop’s alpha male, but he was elderly and less formidable than the average young male.
Fortunately for Yakei, no other macaques attempted to usurp her throne this season and the queen remained the troop’s alpha at the end of March, according to reserve officials. Her continued rule has surprised scientists and given them an opportunity to observe how macaque society functions under a matriarchy.
Despite having to maintain her supremacy, Yakei managed to have a successful breeding season. After Goro gave her the cold shoulder, she spent many weeks playing the field, expressing interest in no fewer than five males. Among these males was Chris, a male ranked 10th in the troop, and Shikao, who holds the rank just below Chris. But the only male the reserve is sure she mated with was Maruo.
At 15th in the troop, Maruo isn’t ranked very high. But reserve staff members say he is quite the catch.
“He is very calm and kind to baby monkeys,” said Tadatoshi Shimomura, a guide who has been with the reserve for the past 30 years.
As a mother, this might be important to Yakei. In the summer of 2019, Yakei gave birth to twins, which is rare for Japanese macaques. One of her babies went missing and is presumed to have died, but Yakei continues to care for the other.
Although a mature Yakei fought with her own mother to rise in status, “she is generous and kind to her baby,” Mr. Shimomura said.
It seems that Yakei held onto power during this breeding season without much fuss. The only changes in rank occurred when the monkey that held the No. 3 spot went missing and all the monkeys below him moved up in rank by one.
“As a female, Yakei should be physically much weaker than other adult males and so it should be easy for them to outrank her by attacking and defeating her,” Yu Kaigaishi, a research fellow at the Japan Society for the Promotion of Science, said in an email. “I guess Yakei got many social allies after becoming alpha in the troop, which could make her position stable.”
Mr. Kaigaishi, who studies the behavior of Japanese macaques and has observed Yakei and her troop, believes Yakei’s ability to remain No. 1 is evidence that strength isn’t everything in Japanese macaque society.
“Social smarts are more important than physical strength for Japanese macaques,” said Katherine Cronin of the Lincoln Park Zoo in Chicago, who studies animal social behavior and cognition, including of her zoo’s own Japanese macaques. “Macaques who obtain high rank typically have a lot of social support in the form of allies in the troop who help them out when times are tense, such as during breeding season.”
Whether it was because of her ability to amass allies or instill fear in her enemies, Yakei was able to hold onto power, defying macaque social norms. Her behavior has fascinated scientists and brought attention from people around the world.
But her triumphs and tribulations also shed light on how much remains to be learned about the social lives of nonhuman primates.
“The more we observe primate behavior in different environments, including accredited zoos and sanctuaries, the more we learn about how flexible, creative and socially savvy they are,” Dr. Cronin said. “I’m glad that so many people had a chance to learn about the fascinating and flexible social world of macaques. Although they have been studied longer than almost any other primate species, they continue to fascinate and surprise us.”
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