YAMANOUCHI, Nagano Prefecture—Visitors to the popular monkey park here have been delighted by the sight of wild Japanese macaques soaking in hot springs to escape the winter chill. Approximately ...

The resident Japanese macaque monkeys and sika deer have developed a close, mutually beneficial inter-species bond. The macaques ride around the island on the deers’ backs like miniature jockeys, ...

“We love monkeys—we’re on their side,” he said. “We don’t use abusive training methods.” Kaoru Amagai lives in a traditional Japanese home in Ota, Gunma, with three pet macaque ...

Research on Japanese macaques indicates that self-scratching, a response linked to negative emotions, predicts pessimistic judgment bias, where monkeys avoid ambiguous choices after scratching.