Japanese Macaque

The Japanese macaque, also known as the snow monkey, is a terrestrial Old World monkey species native to Japan, although an introduced free-ranging population has been living near Laredo, Texas since 1972. It is the most northern-living as well as the most polar-living non-human primate. In Japan, they were historically known as saru ("monkey"). Nihonzaru (Nihon "Japan" + saru) is used in modern times to distinguish from other primates. Individuals have brown-gray fur, a red face, and a short tail.

Range and diet

The Japanese macaque is diurnal and spends most of its time in forests. It lives in a variety of forest-types, including subtropical to subalpine, deciduous, broadleaf, and evergreen forests, below 1500 m. It feeds on seeds, roots, buds, fruit, invertebrates, berries, leaves, eggs, fungi, bark, cereals and in rare cases even fish. It has a body length ranging from 79 to 95 cm, with a tail length of approximately 10 cm. Males weigh from 10 to 14 kg, females, around 5.5 kg.

The Japanese macaque lives in mountainous areas of Honshū, Japan. It survives winter temperatures below -15 °C (5°F), and is perhaps most notable for the amount of time it spends in naturally heated volcanic hot springs in Snow Monkey park located in Yamanouchi town, close to a historical hot spring area named Shibu Onsen. In Life on Earth from 1979, David Attenborough notes that the monkeys (not the entire population) first moved into the volcanic area with the springs, "Only a few years ago."

Social organization and reproduction

The Japanese macaque lives in troops 20-100 individuals in size usually subdivided into matrilineal groups consisting of many females and several males. On average, females outnumber males by 3 to 1. The females have a rigid hierarchy with infants inheriting their mother's rank. The males tend to be transient within the troop but in Jigokudani park a line of alpha males, "chiefs", has been documented.

Females will copulate with an average of ten males during the mating season, though only about one third of the mountings will lead to ejaculation. Though pregnancies only occur during the mating season, heterosexual and homosexual relations go on year-round.

The Japanese macaques at Jigokudani hotspring in Nagano have become notable for their winter visits to the spa.

After a gestation period of 173 days, females bear only one baby, which weighs about 500 g at birth. This macaque has an average lifespan of 30 years.


The Japanese macaque is a very intelligent species. It is the only animal other than humans and raccoons that is known to wash its food before eating it. Researchers studying this species left sweet potatoes out on the beach for them to feed on, then witnessed one female, named Imo (Japanese for yam or potato), taking the food down to the sea to wash the sand off it. After a while, others started to copy her behavior. This trait was then passed on from generation to generation, until eventually, all except the very oldest members of the troop were washing their food and even seasoning their clean food in the sea. She was similarly the first observed balling up wheat with air pockets, throwing it into the water, and waiting for it to float back up before picking it up and eating it free from dirt. An entirely altered misaccount of this incident is the basis for the fictitious "Hundredth Monkey" meme.

The macaque has other unusual behaviors, including bathing together in hot springs and rolling snowballs for fun. Also in recent studies, it has been found that the Japanese Macaque can develop different accents, like humans. It was found that macaques in areas separated by only a couple hundred miles can have very different pitches in their calls, their form of communication. The Japanese Macaque has been involved in many studies concerning neuroscience and also is used in drug testing.



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