A profusion of pressurized penguin poo

Apr 06 2012 Published by scicurious under Friday Weird Science

Or, as noted "Penguins shooting the s**t".


Today's weird science comes to you courtesy of Anne Jefferson of Highly Allocthonous, who pointed Sci to this paper purely for the amazingness that is Figure 1. And it IS amazing.
After all, what do you get when you combine penguins and poo? SCIENCE of course!
Meyer-Rochow and Gal. "Pressures produced when penguins pooh—calculations on avian defaecation" Polar Biology, 2003.


What do you usually think of when you think of birds gathered together? You think of a lot of feathers, a lot of noise...and a lot of bird crap everywhere. Penguins, especially, face this problem when they come ashore to nest and incubate their eggs. You'd think with all that penguin in all that nest for all that time...well things in the nest would get pretty disgusting.

But penguins, it turns out, are pretty tidy nest keepers. When they are sitting on their egg and realize they gotta go, they head to the edge of their stone nest, aim butt outwards, lift the tail, and SHOOT.
And they really shoot! As you saw in the video, they get some distance. But the question is...HOW does this happen? The penguins presumably have to produce some poo pressure, but just how much?
Enter these researchers (who definitely had fun in the writeup, I really wish my research writeups were this fun!). Since penguins are all protected and you're not supposed to get closer than 5m to a penguin in the wild, they decided to run a modeling calculation of how much pressure a penguin would have produce to adequately propel their poo.

What variables do you need to consider when you are contemplating penguin poo pressure? First, you need to consider how WIDE the opening of your "gun" is. using "a few 'spot-on' photographs", taken during the event, they estimated the diameter of the cloaca during at about 8mm when the penguin pinches a loaf. You then need to work out height. As the penguin moves up to the edge of its nest to do its business, the cloaca is going to be a bit higher than normal, around 20cm. And then you need to determine the viscosity of your poo, whether its more liquidy or more solid. Once you have all of these and the distance the poo travels, you can calculate the velocity of the dump using this model:

(This may very well be the BEST figure in science. Even compared with the rats in pants, though I feel that figure has more of an attempt at gravitas.)

Once you have an idea of velocity, you can start working out pressure for fluids of different viscosities. The authors started out with the "ideal" viscosity of something near water. While they got a pressure of around 34mmHg (not too bad), the low viscosity, and the constant pressure, would result in the poo taking on a parabola. This would be great if the penguin could REALLY get its butt in the air, but since it stands upright and can't...it may be implausible.

However, a higher viscosity works better. If you use a viscosity of say...below glycerine, but above glycol (they tried to take poo samples and measure the viscosity directly, but things like bits of shrimp and fish bones and scales kept getting in the way. The things people will do for science), and you assume that you're working with only initial pressure (to propel the mass away from the nest, but relax immediately after), you get a pressure between 77 and 450 mmHg. This number takes into account friction in the intestintal tract.

That's a lot of pressure. Really. Humans usually poop at around 55mmHg (100 if you're feeling stopped up). So up to 450mmHg is pretty substantial. And it'd be interesting to look at the muscles and see how they do it (also the authors refer to "non-Newtonian mechanisms of mucus participation", which, whatever it is, is probably both awesome and kind of gross).

Future studies (when the authors get back to Antartica, where they apparently had enough free time for this) are going to look at other important variables in penguin poo, like the direction of wind, and whether this changes where the penguin aims its poo. I eagerly await more studies of penguin and how they shoot the s**t.

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

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