The animal is small, around the size of a rat or pigeon. Its activity level is on par with a rat, but it can fly and is rather more intelligent, and thus uses more energy. Their excretory system produces uric acide as in birds. It is omnivorous, and the relevant population has a diet consisting of around 20% fresh fruit, 20% insects and small prey, 10% foliage and grass, 10% mushrooms, 10% wood and paper, and 30% processed foods from humans. They also have gastroliths

It has a chimeric digestive tract with many organs. Its mouth has grinding molars as in many herbivorous mammals, which it uses to grind up the food it eats. Its teeth can also chew other sorts of food like most omnivores. They chew their cud when digesting foliage or woody matter. The stomach is a 5-chambered structure where each part is used as required. The chambers are the crop, which stores food, the rumen and reticulum, which ferment wood and leafy material as in ruminants, the stomach-proper, which works as a stomach usually does, and a gizzard, which helps rechew meat and other such foods that bypassed the fermenting stage. They have a liver, but no gallbladder or distinct pancreas. Their small intestine has a spiral valve like the intestine of a shark, but they also have a large intestine that ascends and descends as in mammals. They don't have much of a caecum. At the end of the digestive tract is a rectum in which the feces is stored. They do not have a cloaca

Given its diet and the structure and processes of its digestive tract, what sort of fecal matter would they produce?

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    $\begingroup$ does it use urea like a mammal or uric acid like a bird, otherwise its the same as a rodent or bat dropping of the same size and water intake. $\endgroup$
    – John
    Commented Aug 17, 2022 at 13:02
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    $\begingroup$ Ah yes, Worldbuilding.se asking the important questions: what does this poop look like? (I would answer, but I am simply not qualified for this!) $\endgroup$
    – PipperChip
    Commented Aug 17, 2022 at 17:03
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    $\begingroup$ Can you clarify which aspects of this animal's biology are significantly different than a pigeon's? I see the bit with the shark intestine, but it confuses me - a Nikola Tesla valve seems hard to place here, and a slow digestive process seems incompatible with flight. Also, you stop at the rectum but the coprodaeum and cloaca (if present) would be of special importance. $\endgroup$ Commented Aug 17, 2022 at 21:09
  • $\begingroup$ Check out the Hoatzin. $\endgroup$
    – Daron
    Commented Aug 19, 2022 at 11:24
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    $\begingroup$ I've added the [poo] tag to the question. $\endgroup$
    – Daron
    Commented Aug 19, 2022 at 11:29

2 Answers 2


Given that this creature produces uric acid rather than urine, but does not have a cloaca, then its uric acid excretions would be seperate from its digestive excrement, and need not be excreted simultaneously as they are in birds.

So, there would be renal excretions, consisting of a white splat of uric acid, much as is the case with birds, save that no digestive excrement would necessarily be present.

Of more interest would be the digestive excretions. Given this animal's varied diet, its feces would also vary according to what it had been eating recently. Fruit, insects, small vertebrates and fleshy invertebrates, mushrooms and processed food would contribute a soft, pasty material to the feces, with the inclusion of seeds if eaten with fruit, and finely divided exo/endo-skeletal material if present in the diet.

Foliage, grass, wood and paper would be present in the feces as finely divided and partially digested particles.

Given the lack of a gall bladder, bile would be produced and excreted at a constant rate rather than being released as required, so all the feces would be a uniform brown colour. Given the multi-part digestive system, the different components of the feces would tend to be excreted seperately rather than being intermixed, leading to droppings with different consistencies.



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Flying animals need to be super lightweight. They cannot afford to sit around for hours fermenting their bodyweight worth of plant matter.

Your creature only holds a small amount of food at a time. The food stays in the body for an hour or so and is partially digested. The simple carbohydrates and other highly reactive compounds are extracted. The remaining fats and complex proteins are sprayed out the other end as the creature majestically takes flight.

Because the food passes through the animal so quickly, it needs to be loose and sloshy. It is still loose and sloshy when it comes out the bumhole.


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