Japanese scientists spent nine years filming the members of Mozu's monkey troop as they foraged, fought, and played in the forests and hot pools of the Yokoyu River valley. Season after season, the filmmakers documented every aspect of snow monkey life -- from the midnight birth of a new troop member, the first macaque birth ever to be filmed, to the haunting death of a female elder, who spends the final months of her otherwise highly social life in solitary exile. This constant contact with the troop allowed the filmmakers to come to know the monkeys as individuals, capturing forever the special courage that made Mozu far more than just another subject of a scientific study.

Up to 60,000 of the three-foot high, red-faced monkeys, known to scientists as Macaca fuscata, live in Japan's hilly forests. Wild bands usually contain 20 to 30 members and move quickly through the trees in search of fruit and other food, making it difficult for scientists to study them. To cope with this problem, beginning in the 1950s, Japanese researchers created more than a dozen feeding stations designed to draw the monkeys out in the open where they could be observed. Some of these stations evolved into formal parks that allow both scientists and tourists to watch snow monkeys carry out their complex, highly-structured social lives.

One such park was Mozu's home. The Jigokudani Monkey Park near Nagano, less than a mile from the 1998 Winter Olympics' ski slopes, shelters more than 200 macaques living in three troops. Though the monkeys are fed daily in the park, they spend up to 80 percent of their time foraging in the surrounding forests. They also spend hours soaking in specially-built hot spring pools in the park, a behavior unique to the park's monkeys that some researchers believe the macaques learned by watching local residents bathe in outdoor hot tubs. Whatever the explanation, the warm pools provide a welcome respite from the region's snowy, frigid winters.

By observing the monkeys at Jigokudani and other study areas, researchers have made important discoveries about how macaques learn, communicate, and organize their troops.

Today, however, scientists disagree on whether macaques learn by imitation. "There is little evidence they learn by watching others, though they certainly are curious," says primatologist Joan Silk of the University of California, Los Angeles. Instead, she believes, macaques "learn by trial and error, and they don't really learn very fast" compared to other primates.

The debate highlights how much there still is to learn about snow monkeys, even though they are already among the world's most-studied primates. At Jigokudani, for instance, researchers recently studied the common practice of social grooming, in which macaques pick bits of dirt and parasites out of one another's fur. The study hinted at an advantage for both parties -- the groomee gets clean and parasite-free, while the groomer gets a tasty meal of insects and eggs -- but more study is needed to confirm the monkeys' motivation. Similarly, some of the mellow coos and high-pitched cries snow monkeys use to call for help when they get into fights remain poorly understood by humans.

Photos: Masashi Koizumi.