The many (scientific) uses of penguin poop (Part III)

How hard does a penguin push?

Remember to read the newest and indeed first edition of the Carnal Carnival featuring many other stories about poop!

I’ll admit, I didn’t get the idea to post about penguin poop from the cool and well popularised study on tracking them from space. I got it from a very cool talk by Nathan Myhrvold. This is a guy who got rich working for Microsoft and then quit in 1999 do do random stuff with his money. Like take pictures of whale sex, buy T.Rex skeletons and laser mosquitos to help prevent Malaria. However, he’s not an author on this study so no more shall be said about  him now. For more information check out this TED talk.

What’s this all to do with penguin poop? Well, he mentions a paper on the forces involved in penguin pooping. Because penguins are protected you cannot just go and measure the forces on a wild penguin. Instead, the authors relied in photographs. They used the previously mentioned Adelie penguin and the closely related Chinstrap penguin (picture below from wikipedia) again both of the genus Pygoscelis.

When these penguin poop on land (via a cloaca) they stand one the edge of their nest, slightly bend forward and lift their tail and then spray whatever needs to go as far as possible. They reach first around 40cm away and then, as pressure drops, form streaks towards the nest. These streaks go out in every direction from the nest, possibly the penguin chooses the direction based on wind-direction (but no one really knows).

Based on photographs they made the following estimates:

And based on these estimates, they did some fancy calculations. The one further value they needed was the viscosity of penguin poop. They tried taking samples to measure it but because of various fragments of solids such has scales and fish bones in the faeces, they could only estimate that the viscosity is somewhat like that of olive oil.

Now on to the results. The pressures produced by penguins lie between 77mmHG and 450 mmHg. For comparison, the human rectum muscles can withstand pressures up to 55mmHg, any higher and the contents are expelled. When straining, pressures up to 100mmHg can be reached. So no matter how hard you try to poop, a penguin can do it harder.

The authors call these “Cautionary Conclusions” seeing as all values are based on estimates. Still, I find it a fascinating topic, probably because it’s such a random thing to think about. And the drawing of the penguin is kind of cute if you forget that it’s pooping.

Of course, the remaining question is WHY do penguins do this. The obvious answer is to keep their feathers clean. Many birds actually poop like this, though I don’t know of another study about pressures. Because of a penguin’s posture, they cannot bend forward as much as other birds to increase their range. It has been estimated that eagles poop at an angle between 15° and 30° which would need lower pressures to achieve the same distance.

Obviously, further studies are needed. Who doesn’t want to study eagle poop?

Meyer-Rochow, V., & Gal, J. (2003). Pressures produced when penguins pooh?calculations on avian defaecation Polar Biology, 27 (1), 56-58 DOI: 10.1007/s00300-003-0563-3