Humans eat lots of weird stuff, but one thing we almost never eat is poop,

either because we're naturally grossed out by it, or because we've learned that poop contains nasty pathogens.

But for lots of animals, feces is a regular part of the menu.

That's partly because poop isn't necessarily as dangerous as we think.

While poops from sick individuals can contain disease-causing bacteria, viruses, and parasites — and contaminate anything they touch —

healthy poops are usually just water, harmless bacteria, undigested food, and some metabolic waste and dead cells.

Poison control centers consider accidental ingestion of poop, human or otherwise, to be minimally toxic.

And doctors even prescribe poop pills from healthy people to combat hard-to-treat gut infections.

And because the digestive process doesn't usually manage to suck all the nutrients out of food, poop is nutritious.

Herbivores, for example, leave a third of food nutrients in their poop.

As a result, animals like dung beetles and flies subsist almost entirely on nutrients from the poop of other animals.

And for thousands of years, humans have built toilets over pigsties because pigs can get almost all of their nutrition from human poop.

And while some dogs will snarf down pretty much any poop they come across,

lots of dogs will actually use their keen noses to sniff out fresh poop that has specific vitamins or enzymes they're craving.

And some animals regularly extract leftover nutrients from their own poop.

For example, when gorillas feed on the hard seeds of the Dialium tree,

their gut bacteria soften the tough seeds but don't extract many nutrients.

So when times are tough, gorillas will often eat their excrement to extract the seeds' full complement of fat and sodium.

And when the southern cassowary eats cassowary plums,

the fruits are so big and the bird's digestive tract is so short that the cassowary poops out whole chunks of the fruit;

it then turns around and picks them out to eat, and digest, again.

Other animals absolutely have to eat their own poop.

For example, rabbits eat lots of the same foods that ruminants like cows do,

but while cows have long, complex digestive tracts that give the microbes inside time to break down the tough plant cells,

rabbits have much shorter guts.

So, after a yummy plant meal, they poop a soft mucus-covered cluster that contains the partially digested food and the microbes in charge of digesting it.

Then they gobble the whole package back up in order to recover the nutrients and bring the microbes back into their guts.

Finally, the rabbit poops real rabbit poop.

Koalas, too, must eat their own poop.

Or at least their own mom's poop.

They have a specialized diet of eucalyptus leaves,

which are both fibrous and toxic, and koala babies aren't born with the specialized bacteria needed to break it down.

So for several weeks, the baby just eats pap:

a soft, green poop chock-full of those bacteria that the mom makes special for her little one.

Pap both supplies nutrients and gives the baby the microbes it needs to digest its future food.

As baby food goes, this number 2 is second to none.

Feeding your baby poop is a pretty strange strategy.

But feeding your baby to a predator is an even stranger one.

When a quokka mom gets cornered, she sometimes ejects a helpless joey from her pouch and runs the other way.

And this actually sort of makes sense, she has a spare!