Japanese institute opens memorial site for famed chimpanzee Ai

Photo taken around 2024 shows the female chimpanzee Ai taking part in an experiment.Photo courtesy of the Institute for the Evolutionary Origins of Human Behavior, Kyoto University, Kyodo News About six months after the death of Ai — a female chimpanzee celebrated as a "genius" for her ability to understand numbers and identify colors — researchers at Kyoto University are honoring her legacy through a memorial website that continues to attract visitors. The Institute for the Evolutionary Origins of Human Behavior at Kyoto University opened the tribute site in February after receiving a flood of condolence messages following Ai's death in January at the age of 49.

"You taught us things that will continue to live on within us," reads a message on the memorial website. Ikuma Adachi, an associate professor at the institute who worked with Ai as a research "partner" from 2008, said he hopes the website will allow people to remember her life and scientific contributions, adding that it will continue to be updated. Ikuma Adachi, an associate professor of the Institute for the Evolutionary Origins of Human Behavior at Kyoto University, shows a memorial website for the chimpanzee Ai displayed on a computer screen in Inuyama, Aichi Prefecture, on April 24, 2026.

Provided by Kyodo News Born in Africa, Ai arrived at the institute, then known as the Primate Research Institute, in Inuyama, Aichi Prefecture, in 1977 at an estimated age of one. The following year, she began language-learning studies using a computer-linked keyboard. For nearly five decades, she contributed to research into chimpanzee cognition, including studies on learning and memory.

"Ai was exceptionally curious and always approached experiments with great enthusiasm," Adachi said. Photo taken on April 24, 2026, shows a memorial altar for the chimpanzee Ai at the Institute for the Evolutionary Origins of Human Behavior at Kyoto University in Kyoto.Provided by Kyodo News Ai became internationally known after a study published in the British scientific journal Nature in 1985 demonstrated her ability to use Arabic numerals to represent quantities.

Other experiments showed she could distinguish between larger and smaller numbers and understand kanji representing colors. She also made headlines in 1989 when she escaped from her enclosure, apparently after using a nearby key to open a padlock. Despite her reputation, Adachi said Ai should not be viewed as an extraordinary "genius."

"She was not a special genius," he said, explaining that other chimpanzees can develop similar abilities if given appropriate methods and environments. What made Ai different, he said, was her intense curiosity. She eagerly anticipated experiment sessions every day and readily embraced new equipment and experimental settings.

Many chimpanzees hesitate when faced with unfamiliar settings, but Ai approached new experiments proactively, Adachi said. Adachi said Ai was also a keen observer of people and sometimes appeared to size up newly arrived researchers. "She taught me how to interact with chimpanzees," he said.

In 2000, Ai gave birth to a son, Ayumu, through artificial insemination. Ayumu has also demonstrated strong cognitive abilities and attracted attention from researchers. In her later years, Ai seemed to enjoy interacting with researchers more than participating in experiments.

Even as her health deteriorated, she continued participating in experiments until the day before her death. She died on Jan. 9 from old age and multiple organ failure, surrounded by many researchers and staff members.

Following her death, the institute received numerous phone calls and emails expressing condolences and gratitude. The response prompted the institute to launch the memorial website in February. Operated by Adachi's laboratory, the website features messages of condolence and links to a blog where researchers share memories of Ai.

Adachi said visits to the blog have continued to increase. A handmade memorial altar has been set up in a corner of the laboratory, with Ai's favorite grape juice placed there as an offering. The institute also plans to continue publishing scientific papers based on experiments in which Ai participated.

"I want to thank her for supporting our research for such a long time," Adachi said. "I want to tell her, 'You did a great job.'" Photo taken in October 2005 shows the "genius" female chimpanzee Ai.

Photo courtesy of the Institute for the Evolutionary Origins of Human Behavior, Kyoto University, Kyodo News Biology