Retrospectacle: A Neuroscience Blog

[This is part of a series I'm doing here on Retrospectacle called 'Science Vault.' Pretty much I'm just going to dig back into the forgotten and moldering annuls of scientific publications to find weird and interesting studies that very likely would never be published or done today (and perhaps never should have.) I'll probably try to do it once a week (and if you have suggestions, please do email me with them.)]

For this weeks 'Science Vault, I didn't really have to reach too far back in time to find something utterly ridiculous and slightly ribald. Nay dear reader, in 2003 the journal Polar Biology published a gem of a paper entitled 'Pressures produced when penguins pooh--calculations on avian defecation.' (pdf) by Benno et al. Apparently, a few types of penguins are naturally endowed with the special ability of not crapping in their nests. That is, they have sufficient...er.....gastrointestinal pressures (snicker snicker) to...uh....propel their poop away from them. Obviously, the distance and trajectory of this unique penguin pooping should be measured and documented, then published for the good of all mankind!

(Read on for all the explosive details.....)

Now, from the author's mouths:

The pressures involved [in the projectile pooping] can be approximated if the following parameters are known: (1) distance the fecal material travels before it hits the ground, (2) density and viscosity of the material, and (3) shape, aperture, and height above the ground of the orificium venti.

So, the goal was to estimate what the force of the "pressure" was by observing the physics of the pooping process and the characteristics of the poop itself and of the [shudder] orifice involved.

Now, what exactly are we talking about here? Well if you need visual confirmation of this (now) well-documented phenomena, why just cast thine eyes downward to this rare YouTube footage.

During the brooding season, when penguins are sitting on their nests, they don't want to leave their nests and thereby leaving their eggs open to predation. This would make for an uncomfortable situation when nature called, so they evolved the ability to poop without ever leaving the nest. The bird moves to the edge of the nest, lifts their tail, and "shoots."

The authors observed these penguins "in the act," and are meticulous in their pooply descriptions:

The expelled material hits the ground maximally 40±12 cm away from the bird and then leaves behind a whitish or pinkish streak that can end a few centimetres from the nest
s periphery and may be up to 1 cm wide. The colour of the streak depends on whether the penguin had enjoyed a meal of fish (mostly white) or krill (pinkish). According to Jackson (1992), the time required to excrete 50% of the total faecal mass is 9.1 h and 14.5 h for fish and prawn food, respectively.

They estimated that the orifice had a maximum diameter of 8 mm "at the moment of firing," (ew) and that the penguin's rear was around 20 +/- 6 cm above the ground. They used this data to infer the pressure required to achieve the distance that the poop had traveled from the nest. For clarification, please refer to the helpful figure below.

Using the Hagan-Poiseuille-equation for dynamic pressure, they determined that the pressure needed to project the poop depended on the viscosity of said poop. Observe Figure 2 (below), which illustrates the dependence of pooping pressure on viscosity.

This necessitated that the authors measure the penguin poop's viscosity with a high-performance viscosimeter (not one of those cheap-o low-performance viscosimeters!). However, the readings were inconsistent due to all the fishbones and shrimp shells in the poop, but their best estimate was that the poop's viscosity matched somewhere around that of olive oil. (Ew ew.) After this final value was obtained, they were able to complete the equation and estimate that the power of a penguin's fart was somewhere in the range of 10kPa to 60 kPa. Bravo.

And just in case you wondered what this meant for humans, well, the authors covered that in the discussion.

The pressures on the rectal muscles in an upright human amount to 20 mmHg and are resisted by the rectal muscles, but when pressures reach 55 mmHg, the external as well as the internal sphincter relaxes and the contents of the rectum are expelled (Ganong 1999). During straining, pressures may rise well above 100 mmHg (Langley and Cheraskin 1958), but it would seem that the pressures regularly produced by penguins to expel their faeces on land are considerably greater, possibly reaching half an atmosphere.

Yeah, thats right. Penguins can fart better than us. Birds rule.