Home » Why Do Apes Eat Their Poop? Eating Feces as a Sign of B12 Deficiency in Zoos.
A big silverback gorilla eating his own excrement
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Why Do Apes Eat Their Poop? Eating Feces as a Sign of B12 Deficiency in Zoos.

Many are unaware that poop-eating is a sign of nutritional deficiencies, in particular, B12 deficiency! Feces-eating apes are often seen as disgusting, funny, or just stupid! But primates are none of that! Eating poop (coprophagy) is a form of supplementing nutrition and thus happens more in unnatural settings – in zoos – and is a serious indication of a needed dietary adjustment of apes in zoos towards a more natural, tropical, fruit-rich diet (read our article on the misunderstood frugivorous diet in captive apes here).

Coprophagy in apes – why do the animals eat their excrements?

Coprophagy in animals is known to be a form of “naturally supplementing” nutrients – sometimes from other species’ feces (often from herbivores that have an “especially nutritive” microbiome) and sometimes their own feces. One critical vitamin obtained from feces is vitamin B12:

How do Frugivores Get B12? Poop Eating, Insects, and (maybe) the microbiome:

When it comes to the microbiome as a source of vitamin B12, there seems to be a critical anatomical problem in non-ruminant mammals, like apes and humans: Vitamin B12 is synthesized in the intestines, but it is excreted without being absorbed (Read here why this might not necessarily be the case). This apparent “anatomical issue” is addressed by animals eating their own feces (or other species’ feces) – and with it the excreted vitamin B12. This behavior is called “coprophagy” and has several benefits, like taking in nutrients, undigested foods, and adding to a healthy microbiome.

Excrements can be a natural B12-“supplement” for many animals, including apes.

Is coprophagy really a natural behavior?

Apes are known to be coprophagous in captivity. This behavior is very rare in the wild! Why does it happen more often in captivity?

When looking at vitamin B12 in humans, we learn that the intestinal absorption of B12 is possible under natural conditions and an optimal diet. The same seems to be true for other apes, where vitamin B12 deficiency is a bigger issue in captivity, than under natural conditions! In the wild, apes eat their species-specific diet and thus have a healthier microbiome, which is able to provide the host with B12!

However, coprophagy serves additional health purposes like increasing beneficial intestinal bacteria in gorillas:

Gorillas have been shown to strengthen the microbiome of infants, besides obtaining B12 by eating their feces:

“Coprophagy may also provide gorillas with vitamin B12, produced by bacteria in the hindgut, but only able to be absorbed in the foregut.”

Cooper & Redmond, 2017

It’s important to note that the diet of gorillas is herbivorous (frugivore-folivores), which makes their feces to be of a different consistency than that of omnivores or carnivores. Coprophagy is generally observed with the feces of plant-eaters. For example, dogs tend to eat horse or goose excrement.

Chimpanzees – which are omnivorous frugivores – eat their poop from time to time, but not regularly. Despite the fact that the frugivores are easily repulsed by touching weird, unknown things (like in humans, disgust serves as a protective instinct), but do not seem to be disgusted by their excrements – which illustrates that this is a vital, nutritionally-driven behavior. It must be noted that the feces of plant-eaters, especially herbivores (but probably also frugivores), are different than those of animal-based diets – which explains why dogs (omnivores) like to eat the poop of herbivores (i.e., horses).

We need to be aware that we mostly observe animals eating feces to obtain vitamin B12 in unnatural habitats, like zoos and domestic animals! In the wild, most apes are highly herbivorous, but get B12 from insects or other small amounts of animal foods. They “supplement” less B12 through feces.


Eating feces seems to be a last-resort solution to combat B12 deficiency in animals, including frugivorous apes: they usually eat B12-rich insects in the wild and have a natural microbiome that may contribute to providing vitamin B12 to the host.

Eating poop is not funny or stupid, but an indication that the diets of apes in captivity are often not natural and could contribute to a shortcoming in vitamin B12. Read more about the diet of apes in captivity here:

Read also our article:

Please, Zoos, Fruit-up the Diets of Primates! Why the “No Bananas” Policy is Cruel…

Read also our article:

What do Chimpanzees Eat in the Wild? The Role of Fruits and Meat.


  1. Intestinal bacteria as a vitamin B12 source (no date) VeganHealth.org. Available at: https://veganhealth.org/vitamin-b12/intestinal-bacteria-as-b12-source/ (Accessed: April 5, 2023). 
  2. Prates, H.M. and Bicca-Marques, J.C. (2005) ‘Coprophagy in captive Brown Capuchin Monkeys (Cebus apella)’, Neotropical Primates, 13(3), pp. 18–21. doi:10.1896/1413-4705.13.3.18. 
  3. Sakamaki, T. (2009) ‘Coprophagy in wild bonobos (Pan Paniscus) at Wamba in the Democratic Republic of the Congo: A possibly adaptive strategy?’, Primates, 51(1), pp. 87–90. doi:10.1007/s10329-009-0167-9. 
  4. Coprophagy (no date) Coprophagy – an overview | ScienceDirect Topics. Available at: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/coprophagy (Accessed: 28 May 2023). 
  5. Kyoto University. “What grosses out a chimpanzee? The origins of disgust: Origins of disgust.” ScienceDaily. ScienceDaily, 17 November 2017. <www.sciencedaily.com/releases/2017/11/171117103820.htm>.

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