Why does grass eaters’ poop look so different?

A goose, a cow and a horse all mainly eat grass. Yet their droppings look completely different. A goose produces a long dry cigar with a white tip, a cow a wet green-brown flan and a horse neat brown figs. How is that possible?

We ask the Zoological Museum Netherlands, a knowledge platform about the interactions between the physique, behavior and living environment of animals. “It is true that animals can have the same diet,” says Kas Koenraads of this foundation, “but species with a different origin and a different structure and way of life can process the same diet very differently.”

There is no straightforward answer, according to Koenraads: it is not the case that a certain gut shape or lifestyle invariably determines how a grass, meat or fish droppings come out. The end product is always the sum of a whole series of factors – and they are different for each species.

First of all, there are already major differences in the way in which animals excrete their waste, says Koenraads. “Birds excrete their urine along with their feces, while mammals have a separate system,” he cites as an example. That explains why a lot of bird droppings are white and wet. The white is uric acid – also at the tip of the goose cigar. But apparently the goose is more economical with its moisture than, for example, a blackbird, which eats berries and worms and defecates much wetter.

Then there’s the cow pie. “A cow has a multiple stomach system and is therefore a typical herbivore,” says Koenraads. The four cow stomachs, together with rumination, ensure efficient digestion of the hard-to-digest plant fibres. You will hardly find it in the poo. „The horse, on the other hand, is a so-called hindgut fermenter, which makes the biggest digestive blow in the large and appendix.” This is faster, but also less efficient: you will find a lot of undigested plant remains in horse droppings.

That cow pie is not natural, by the way. Wild cattle produce much drier, rounder droppings. Cows of our farmers are actually permanently suffering from diarrhea, because of the artificially high protein content of their diet: concentrates and fertilized grass.

And what about wolf, fox, lynx and marten, who all eat meat, but still make different droppings? “In carnivores with a similar diet, the size mainly reveals who the owner is,” says Koenraads. The size of the droppings depends on the size of the animal. In the Netherlands, for example, a wolf is the only one that makes turds up to thirty centimeters long and four centimeters in diameter. A wolf roll also contains a relatively large amount of hair and bone fragments, because a wolf with its strong jaws eats less choosily than, for example, a fox. Martens and foxes also eat vegetable food, which results in a different structure and color.

And finally, otter and heron: both fish eaters. “A heron swallows a fish whole,” says the biologist. “The shape and structure of the stomach and the acidic gastric juices aid in digestion. The heron regurgitates many scales and bones in the form of pellets.” The residual products come out together with the urine: in one wet, slimy bottle.

The otter, on the other hand, has teeth with which it can bite and chew. His stomach therefore needs to be less acidic. His poo therefore contains indigestible parts and is drier, because he excretes his urine separately. A connoisseur will also recognize such a so-called ‘sprint’ by the characteristic otter smell.

Nienke Beintema