Japanese Snow Macaques

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Japanese Snow Macaque

Who says it’s too cold for monkeys in New England? Macaques can be found in more climates and habitats than any other primate except humans. 

Japanese Macaques (Macaca fuscata) occupy the northernmost regions that  range through the forested mountains and highlands of Japan. They thrive in winter temperatures that fall as low as 5ºF with snow more than three feet deep.

More commonly called Snow Monkeys, we are familiar with images of them bathing in hot thermal pools to keep warm in Japan’s icy winters. Interestingly, bathing in hot springs is a learned behavior. In the 1950’s, anthropologists believed that humans were the only animals that pass on learned behaviors from individual to individual and across generations, a process called cultural transmission. Because it is fairly easy to observe Japanese Macaques living in troops in their natural environment, researchers determined that studying their behavior would provide accurate insight into whether they too engage in cultural transmission. Similar studies had been done with captive primates, but captive animals do not engage in natural behaviors.

In 1963, a young female named Mukubili waded into a hot spring in the Nagano Mountains to retrieve some soybeans that had been thrown in by researchers who were  provisioning the monkeys with food in an effort to keep them out of local orchards. She liked the warmth and soon other young monkeys joined her. At first the behavior caught on only with the young macaques and their mothers. Over some years, the rest of the troop took the plunge to find shelter in the 109º hot springs to escape the winter cold.

When they began to invade nearby hot tubs and human spas, it was decided to build the Nagano macaques their own hot springs.

Distinguishing Features

The Japanese macaque is a medium sized, stocky monkey, about 2 to 4 feet long and weighing from 22 to 66 pounds, with a relatively short tail. Males are twice as large as females. Their coats range from gray to brown or mottled in color. In the winter they grow a heavy insulating coat to maintain their body temperatures. During the summer they have a lighter coat.

The Japanese macaque has a very human-like naked face and expressive eyes. In adulthood, the face and bottom become red. Like humans, all macaques have opposable thumbs that they use to manipulate objects. They use all four limbs to get around, but also walk just on their hind legs when holding something in both hands. They are very capable climbers and sleep in trees, either individually or snuggling together to keep warm. They do not make nests and they change sleep sites daily.

Diet and Lifestyle

Japanese macaques are adaptable frugivores, eating mostly fruit, as well as seeds, young leaves, flowers, tree bark, fungi, bird eggs, insects, and invertebrates such as snail, crabs and crayfish. The variety in their diet is mostly due to seasonal changes and the resulting abundance of food, as well as their large habitat range. They prefer to forage on the ground. Because they are primarily fruit eaters, it is likely that they help to disperse seeds.

Most can live to be 25-30 years of age in captivity and 8 to 10 years in the wild. They live in troops usually made up of 20 to 30 individuals, but sometimes including over 100. A major constraint on troop size is food availability.

Females remain in the same troop, usually for life. Rank for females is inherited matrilineally, with daughters receiving the rank of their mothers. Younger offspring are ranked higher than older siblings, so there is no advantage to being the first-born of a high-ranking mother.

There are strong social bonds between the members of a troop, especially among females. Females select their mate according to the rank of the male and how long he has been in the troop. She avoids choosing males whom she has mated within the past 4-5 years. Therefore, the longer a male is in a troop, the fewer mating opportunities he has. For this reason, males often change troops. This mating strategy not only increases genetic diversity, but can also lessen the chances of inbreeding by offspring.

Males disperse from the troop around the time they reach sexual maturity and transfer among troops throughout their lives. Males emigrate to a new troop every 2-4 years, usually during mating season.

As with other primates, infant dependency is long. Males help with parental care. They carry young, huddle with them, groom and protect them.

Behavior and Play

Japanese macaques are gentle creatures that display frequent social interactions. They are seldom aggressive. Grooming helps maintain the intricate social bonds between them. Grooming partners reflect not only kinship lines, but also the group’s dominance hierarchy.

Young macaques spend a lot of time playing. They make snowballs and roll them along the ground to make them larger, just as we all did as children. This activity has no survival purpose. Entire troops of Japanese macaques engage in the activity simply because it is fun.

Culture and Communication

Provisioning of Japanese macaques with food has led to special developments and fascinating observations of their culture. One famous example of this is potato washing in a troop in Koshima, Japan. When researchers provisioned a troop by putting sweet potatoes along the beach to bring them out into the open, one old female named Imo began to wash the sand off of her sweet potato in water instead of brushing it off with her hand. Over time, this behavior spread to other members of the troop and was passed along from generation to generation. Potato washing became even more modified as they began washing their sweet potatoes in salt water rather than fresh to enhance the flavor.

Communication in all macaques is varied and complex. They usually use some combination of visual signals, vocalizations, and physical contact. Their bare faces, mobile lips, dramatic eyes, and body posture are used to successfully convey information about their moods and environment.

Conservation Status

Snow monkeys, like many other primates, are threatened by habitat destruction and human over population. They live mainly in reserves, and in many cases, depend upon supplemental feeding by humans to survive the winter conditions.

As more development takes place in Japan, encounters between Japanese macaques and humans are becoming more frequent. They raid crops and are considered to be agricultural pests. As a result, they are shot; about 5,000 are killed per year, despite protection from the Japanese government. Snow monkeys have been officially protected in Japan since 1947. However, the rights of farmers have taken precedence over laws protecting the macaques that  eat their crops.

Today Japanese macaques are listed as threatened by the US Endangered Species Act. The subspecies found in Yakushima, Japan, is listed as endangered.

Like other primates, snow monkeys are capable of contracting many of the same diseases as humans. As a result, they are deemed useful for medical studies and research purposes.

The 100th Monkey

The story of Imo’s potato washing is retold in the book The 100th Monkey by Ken Keyes, Jr. as a parable to relate how cultural transmission can affect the collective unconscious to bring about social change. A moral of this story might be that threats of extinction can be reversed as a direct result of increased awareness and, most importantly, action toward change.

from New England Primate Sanctuary's Staying Connected, Spring 2006

View video

of wild Japanese snow macaques

courtesy of ARKive.org: