Monkeys die from a wide range of causes, and which ones pose the greatest threat depends on the species, where they live, and whether they’re young or old. In the wild, the biggest killers are predators, disease, starvation, and humans. In captivity, degenerative diseases like heart failure take the top spot. Most monkey species have surprisingly short median lifespans, often under 12 years, even though some individuals can live past 30.
Predators That Hunt Monkeys
Monkeys are prey for a long list of animals, including leopards, pythons, large monitor lizards, wild dogs, and birds of prey. In Madagascar, the fossa is a major predator of lemurs and other primates. But in Africa, the most specialized monkey hunter is the crowned hawk-eagle. In Uganda’s Kibale National Park, studies found that 83 to 88% of this eagle’s diet consists of monkeys. Smaller species are especially vulnerable to aerial predators, while larger monkeys face greater risk from big cats and large snakes on the ground.
Disease and Infection
Infectious disease is one of the leading causes of monkey death, both in the wild and in captivity. A 25-year review of chimpanzee deaths in accredited U.S. zoos found that infections and inflammatory disease accounted for 26% of all deaths. In the wild, the threat is often more sudden and catastrophic. Large-scale die-offs have been linked to viruses including Ebola, yellow fever, dengue, and monkeypox. In 1995, an Ebola outbreak killed chimpanzees in Côte d’Ivoire’s Taï Forest. In 1956, a previously unknown virus wiped out bonnet macaques and langurs in India’s Kyasanur Forest.
Disease also flows from humans to monkeys. Measles and tuberculosis, both common in people, are deadly in many primate species. As human settlements push closer to forest habitats, these cross-species infections become more frequent and more dangerous for wild populations.
How Humans Drive Monkey Deaths
Human activity is the single largest threat to primate survival worldwide. According to IUCN data, 76% of primate species are threatened by habitat loss from agriculture, 60% by logging, and 31% by livestock ranching. Road construction, mining, oil drilling, and dam building affect smaller but still significant percentages of species. Between 1990 and 2010, agricultural expansion in primate habitats consumed an estimated 1.5 million square kilometers of land, an area roughly three times the size of France.
Hunting is equally devastating. Across mainland Africa, Madagascar, and Asia, hunting and trapping affect 54 to 90% of primate species. In Nigeria and Cameroon alone, roughly 150,000 primate carcasses from 16 species are traded annually as bushmeat. Armed conflicts make things worse: poaching of bonobos and gorillas spiked in the Democratic Republic of the Congo and Rwanda during civil wars. Grauer’s gorilla declined 77% in just two decades, from 17,000 individuals in 1995 to 3,800 by 2015, driven largely by bushmeat hunting tied to mining operations.
Starvation, Drought, and Extreme Heat
When food and water disappear, monkey populations collapse quickly. A study of vervet monkeys in South Africa recorded 46 deaths over a three-and-a-half-year period, with 52% of those deaths concentrated in a single six-month stretch when drought eliminated standing water and stripped food sources to their lowest levels. The pattern was stark: as food availability dropped, mortality climbed. The highest death rates occurred when both food and water were at their scarcest and temperatures were at their peak.
These findings carry serious implications as climate change intensifies drought cycles across tropical and subtropical regions where most primates live. Long-term deforestation has already fragmented 58% of subtropical and 46% of tropical forests, forcing monkeys into smaller, isolated patches where they’re more vulnerable to local food shortages.
Infanticide and Within-Group Violence
Monkeys also kill each other. Infanticide, where a male kills an unrelated infant, has been observed or suspected in at least 64 primate species. The behavior follows a grim reproductive logic: when a nursing infant dies, the mother becomes fertile again sooner, giving the new male a chance to father his own offspring. This has been documented in capuchins, macaques, baboons, geladas, and many other species. Mothers are sometimes injured during these attacks, typically on the arms and legs as they try to protect their infants.
Losing a mother is also a death sentence for young monkeys. In rhesus macaques, an infant that loses its mother in the first six months of life sees its probability of death jump from about 5% to 58%. Even older juveniles face two to three times the normal mortality risk after becoming orphaned.
How Old Age Kills Monkeys
Monkeys that survive predators, disease, and environmental hardship still face the same aging process that affects all mammals. Their immune systems weaken in ways that closely parallel human aging, with similar changes in gene activity and immune cell function. Tooth wear is a major factor for wild monkeys: once teeth deteriorate, an animal can no longer process tough foods and gradually starves.
In captivity, where predation and food scarcity are removed from the equation, degenerative diseases dominate. The zoo chimpanzee study found that nearly 50% of all deaths were degenerative, meaning organ failure, cardiovascular disease, and other conditions of aging. Trauma accounted for 15%, and cancer for about 6%.
How Long Monkeys Typically Live
Maximum lifespans can be impressive. Rhesus macaques have been recorded living past 44 years, and Japanese macaques past 38. But median ages at death tell a very different story. Male rhesus macaques have a median lifespan of just under 8 years. Female rhesus macaques do slightly better at about 10 years. Baboons land around 11 to 12 years for both sexes. Across most macaque species, males die younger than females, a pattern also seen in humans.
These medians reflect the harsh reality that most monkeys die young. Predation, disease, and environmental stress claim a large share of juveniles before they ever reach reproductive age, dragging the average far below what a healthy individual could potentially achieve.
How Monkey Groups Respond to Death
In the days before death, a monkey’s decline is often visible. One aging Japanese macaque male spent about a month near his group’s feeding site, unable to keep up with normal movement. Three days before dying, he was visibly struggling to walk. On his final day, he sat alone and no one approached him.
Troop reactions vary. When dying or recently dead monkeys become infested with maggots, most group members avoid them. In one documented case, nine individuals approached a dying male, sniffed or touched the maggots on his wounds, then jumped back or ran away. But close social partners sometimes behave differently. One alpha female groomed her dying companion’s wound, picking maggots from it without any visible aversion. After another female died, a young daughter of a group member calmly groomed the body for two minutes before walking away. The overall pattern is avoidance, but individual bonds can override that instinct.