Chimpanzees eat their own feces primarily to recover nutrients their bodies didn’t fully absorb the first time around. While it looks revolting by human standards, coprophagy (the technical term for eating feces) serves a real biological purpose for chimps, and it shows up in both wild and captive populations for overlapping but distinct reasons.
Recovering Nutrients From a Second Pass
A chimpanzee’s digestive system doesn’t extract everything useful in a single trip. Vitamins produced by gut bacteria, particularly B12, are synthesized in the lower intestine, past the point where absorption happens efficiently. By eating their own feces, chimps get a second chance to absorb these nutrients higher up in the digestive tract. Wild primates in general appear to use coprophagy, along with insect eating and grooming, as a natural way to obtain B12 and other micronutrients that their standard plant-heavy diet doesn’t always provide in sufficient quantities.
Seeds are another part of the equation. Chimps swallow many fruit seeds whole without chewing them, and these seeds pass through largely undigested. Research on great ape digestion has found that during heavy fruit-eating periods, dry matter digestibility drops by roughly 18% compared to months when chimps eat less fruit, specifically because of all the unmasticated seeds moving through the gut. Those seeds still contain caloric and nutritional value. Eating feces that contain them is essentially a way to reprocess food that wasn’t broken down the first time.
Seasonal Patterns in the Wild
In wild chimpanzee populations, coprophagy isn’t random. It tends to cluster around specific fruiting seasons. Researchers studying a group of orphaned chimpanzees released into Conkouati-Douli National Park in the Republic of Congo found that coprophagy occurred during major periods of feeding on Dialium fruits, a genus of tropical trees that produce small, seed-heavy pods. When chimps gorge on these fruits, their feces contain a higher proportion of undigested material, making a second pass through the gut more nutritionally worthwhile.
This pattern suggests that coprophagy isn’t a sign of starvation or desperation. It’s more like an efficiency strategy. When the available food is high in seeds or fibrous material that resists digestion, chimps are more likely to recycle what comes out. When their diet shifts to more easily digested foods, the behavior drops off.
Why Captive Chimps Do It More Often
Coprophagy is noticeably more common in captive chimpanzees than in wild ones, and the reasons go beyond nutrition. In zoos and sanctuaries, chimps live in environments that are dramatically simpler than a forest. They don’t spend hours foraging, traveling, or navigating complex social dynamics across large territories. That lack of stimulation matters. Captive chimps display a range of abnormal repetitive behaviors, including feces eating, hair plucking, rocking, and self-harm, that are rare or absent in wild populations.
Social history plays a significant role. Chimpanzees that were separated from their mothers early in life, or raised without normal social contact, are more likely to develop these behaviors. Maternal separation can be psychologically traumatic for great apes, and it also deprives young chimps of the chance to learn normal behavioral patterns from watching and imitating adults. A chimp raised in isolation may never develop the full repertoire of foraging, grooming, and play behaviors that would otherwise fill its day.
Researchers have drawn parallels to mental illness in humans, noting that some abnormal behaviors in captive great apes may reflect genuine psychological suffering rather than simple boredom. The distinction matters: a chimp eating feces in the wild during fruit season is doing something functional, while a captive chimp doing it repeatedly in a bare enclosure may be expressing distress.
Why It’s Less Dangerous Than You’d Think
Feces are genuinely full of infectious organisms. Bacteria, viruses, parasitic protozoa, and intestinal worms all thrive in animal waste, which is exactly why most animals have evolved instincts to avoid contact with it. Primates in particular tend to be selective about where they sit, sleep, and eat in relation to fecal matter.
The key detail is that chimps almost exclusively eat their own feces, not the feces of other individuals. This dramatically lowers the risk. Your own waste contains the same parasites and microbes already living inside you, so reingesting them introduces relatively few new threats. The real danger in fecal-oral transmission comes from encountering novel parasites carried by other animals. By sticking to their own output, chimps sidestep most of that risk.
That said, “lower risk” isn’t “no risk.” In populations where individuals live in close quarters, particularly in captivity, the line between self and other gets blurrier. Shared spaces mean shared contamination, and coprophagy in those settings can contribute to parasite cycling within a group even when each chimp targets only its own feces.
Not Just Chimps
Coprophagy is surprisingly common across the animal kingdom. Rabbits depend on it as a core part of their digestive strategy, producing special soft droppings called cecotropes that they eat directly to absorb nutrients their hindgut fermentation produces. Gorillas, other great apes, and many monkey species do it too. Rodents, dogs, and even some bird species engage in feces eating under certain conditions.
In chimps, the behavior sits at an intersection of nutrition, ecology, and psychology. Wild chimps do it strategically when their diet makes it worthwhile. Captive chimps do it more often, sometimes compulsively, when their environment fails to meet their physical and psychological needs. Both versions make sense once you understand what’s driving them, even if neither version makes the behavior any more pleasant to watch.