Wild Snow Macaques subsist mainly on fruit. Those animals living in more temperate regions of their ranges may have this food year round, though often more northern populations suffer in wintertime, unable to fully meet their nutritional requirements. The fruit is often supplemented with young leaves, shoots, and flowers, and in the winter when most items are unavailable, Snow Macaques have been known to eat tree bark or tree buds. Food availability is, in fact, one of the main restrictions on the size of a troop of Snow Macaques. Although troops of up to 100 have been reported, 20 to 30 animals in a group is more normal. A dominant male leads the group, although most males do not remain long in the same troop. After they reach sexual maturity, male Snow Macaques leave their mother's troop and begin a life of wandering from one troop to another. Each time a male is added to a troop, the dominance structure is re-determined, based on physical strength. Females, on the other hand, stay in the same troop for the duration of their lives. They form strong social bonds and groom each other frequently. Rather than fighting for social rank, female Snow Macaques inherit the social position of their mothers. The entire troop usually helps to raise young Snow Macaques, regardless of sex or relation. Snow Macaques are highly intelligent in addition to agile. They often sleep in trees, forage on the ground, and swim in the ocean to catch shellfish. In the winter, Snow Macaques have been observed soaking in thermal pools to warm themselves. These animals communicate through facial expressions and posturing.

Like humans, Snow Macaques have opposable thumbs. The Snow Macaque is characterized by its red face, on which no hair grows. Older animals have redder faces; those of young or sexually immature animals are often lighter. The hair over the rest of the Macaque's body is thick, particularly in winter when the hair grows denser to keep the animal warm. Normally, this coat is colored brown, white, or gray, or it may be a mixture of the colors. Snow Macaques usually reach lengths between 24 and 48 inches (60 to 120) centimeters. Their tails add an additional three to five inches (7.5 to 12.5 centimeters). They weigh between 17.6 and 66 pounds (8 and 30 kilograms). Females are normally smaller than males.

The Snow Macaque ranges through a more northerly region than any other non-human primate. They reside in the highlands of Japan, and are often found in forested or mountainous regions. Their habitat is subject to vast changes in temperature from season to season, and often, troops may move seasonally to avoid this or find food. Humans have invaded the ranges of Snow Macaques, and as a result these animals have become agricultural pests. They have ventured into suburbs of some cities and, sadly, they often are not welcomed near human habitations. Often, they are killed for their transgressions. This sad fact, along with the threat of deforestation, has left populations of Snow Macaques listed as threatened.

The diet of a captive Snow Macaque should reflect the large amount of fruit that this animal eats in the wild.

Snow Macaques usually reach sexual maturity between three and five years of age. Females choose their mates, and develop red rumps when they are ready to mate. The selection process often takes into consideration the male's dominance position within the troop. However, females are more likely to mate with males that have not been in the troop for long periods of time; usually, males they have associated with for more than four or five years are not chosen. Normally, singlets are born after gestation periods lasting five to six months. The vast majority of Snow Macaques seem to be born between April and September. In addition to nursing her infant, the female Snow Macaque will both protect and carry her infant about until it is about two years old.