Mammals
Japanese Macaque
Macaca fuscata · also called snow monkey, Nihonzaru
The Japanese macaque, or snow monkey, is the primate that lives farther north than any other except humans. It endures Japanese mountain winters that drop to −20 °C, and it is famous for two things — bathing in hot springs, and being one of the first animals in which scientists documented culture.
Overview
Japanese macaques live on three of Japan’s four main islands, across an enormous range of climates: warm broadleaf forest in southern Kyushu, temperate woodland on Shikoku and much of Honshu, and snow-covered subalpine forest in the north, where the ground is under deep snow for months. They live in matrilineal troops of a few dozen to over a hundred, in which females remain in their birth group for life and rank is inherited through the mother’s line, while males move between troops as adults.
Coping with the cold
Northern snow monkeys have a thick winter coat, huddle in sleeping clusters, move as little as possible, and shift their diet to bark, evergreen leaves, and buds when fruit and insects vanish. The troop at Jigokudani in Nagano added another trick in the 1960s: soaking in natural hot springs. Immersed in 40-degree water while snow falls around them, the monkeys stay warm and burn less energy, and researchers have found their stress hormones drop while they bathe. It is a learned local custom — most Japanese macaque troops do not do it.
A pioneer of animal culture
The snow monkey helped establish that non-human animals have culture — behaviours invented by individuals and passed socially through a group. On the island of Kōjima, a young female called Imo began washing sweet potatoes in water in the 1950s, and the habit spread through her troop and its descendants; she then invented a way to separate wheat from sand by floating it. Different macaque troops across Japan have their own distinct traditions, from stone-handling “play” to specific foraging techniques, none of them genetically fixed.
Diet and behaviour
Japanese macaques are flexible omnivores, eating whatever each season and habitat offers — from over 200 plant species to insects, eggs, and, for coastal troops, shellfish and seaweed. They store fat in autumn, forage cooperatively, and communicate with a large repertoire of calls, facial expressions, and grooming, which is central to maintaining troop bonds.
Status
The Japanese macaque is Least Concern and its population is increasing — to the point that it is treated as a serious agricultural pest in some regions, where troops raid crops and enter towns, prompting both culling and non-lethal management. Historic threats of habitat loss and hunting have eased, and the main issue now is coexistence between a recovering, adaptable monkey and a rural human landscape.
Japanese Macaque: common questions
Why do Japanese macaques bathe in hot springs?
To stay warm. In the mountains of Nagano, the troop at Jigokudani ("Hell Valley") began entering the natural hot springs in the winter of 1963, reportedly after a young female followed food that had fallen into a pool, and the habit spread through the troop. Sitting in ~40 °C water when the air is well below freezing conserves body heat and energy, and studies have shown that bathing monkeys have lower levels of the stress hormone cortisol. Only certain troops do it — it is a learned local tradition, not an instinct.
Is the Japanese macaque really a "living example" of animal culture?
It is one of the founding cases. In the 1950s, researchers on Kōjima island watched a young female named Imo start washing sand off sweet potatoes in a stream, then in the sea. Over years the behaviour spread — first to her playmates and mother, then through the troop, and down the generations — and she later invented "placer mining," dropping handfuls of sand-and-wheat into water so the sand sank and the grain floated. Different troops across Japan have their own distinct behaviours, and this troop-specific, socially transmitted variation is exactly what biologists mean by animal culture.
How do Japanese macaques survive such cold winters?
With a combination of a dense, insulating winter coat, huddling together in sleeping groups, reducing activity and moving less, choosing sheltered south-facing slopes, and — for some troops — hot-spring bathing. Their diet also shifts in winter to bark, buds, and evergreen leaves when little else is available. Even so, the northern populations lose weight over winter and the harshest years cause deaths, especially among infants and old animals.
Do Japanese macaques cause problems for people?
In parts of rural Japan, yes. As forests have been altered and the monkey population has grown, troops increasingly raid farms and orchards for fruit and vegetables, enter villages, and occasionally become aggressive toward people who feed them or get too close. This has led to culling in some prefectures alongside non-lethal deterrents. In tourist areas such as Arashiyama and Jigokudani, habituated troops are a major draw, which creates its own management challenges.