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The explosive physics of pooping penguins

Updated: Jun 30, 2023


Penguins are known for their ability to huddle together in large groups to keep warm in the freezing temperatures of Antarctica. However, during the brooding season, these birds have a unique behavior that may seem strange to some. When a penguin needs to relieve itself while sitting on its eggs, it will turn its rear end away from the nest and lift its tail to release a projectile of feces. This behavior helps to keep the nest clean while still protecting the eggs from being left unguarded.

In 2003, two physicists became fascinated by this behavior and set out to calculate the pressure that penguins generate to propel their feces away from the nest. Their research earned them a 2005 Ig Nobel Prize and solidified their place in the world of penguin poop enthusiasts. Recently, a team of Japanese scientists has also weighed in on the matter, calculating the projectile trajectory of penguin feces and recalculating the rectal pressure.

According to Victor Benno Meyer-Rochow, a co-author of the original 2003 paper, this research began during an expedition to Antarctica where he was collecting samples of marine worms and terrestrial insects. However, he also took many photographs of the penguins in the area, which he used in lectures. During a seminar at Kitasato University in Japan, a young woman noticed a slide showing a penguin brooding on its nest and asked about the white and pink lines radiating outward. She thought they were decorations and wanted to know how the penguins made them. This question sparked the curiosity of the researchers and led to the discovery of the pressure generated by penguin feces.

Meyer Rochow wrote in a 2019 blog post,

I explained that a penguin stands up moves to the edge of its nest turns around lifts its tail, and then shoots from its rear which leaves a 30-40 cm long streak of semi-liquid whitish stuff behind. "Everybody laughed with the exception of the questioner. She got red on her face and quietly sat down. (The color of the feces depends on the penguin's diet if primarily fish, the poop is white. If the penguin has been feasting on krill, the poop takes on a pinkish hue.)

According to their calculations, penguins are able to generate three times more pressure than humans when releasing their feces. This impressive feat is likely due to the strong muscles in their rectal area, which are needed to push the feces out through the small opening of the cloaca.

Meyer-Rochow believes that this behavior serves an important function for penguins, as it allows them to protect their eggs without leaving them unguarded. It also helps to maintain the cleanliness of the nest, which is essential for the health and well-being of the chicks once they hatch.

The Japanese scientists who recently conducted similar research on penguin feces also found that these birds are able to control the trajectory of their poop, ensuring that it lands a safe distance away from the nest. They were able to calculate the projectile trajectory of the feces and confirm the high levels of pressure generated by penguins when releasing their waste.

One of the most interesting findings is that penguins are able to generate much higher levels of pressure when releasing their feces than humans can. This is likely due to the strong muscles in their rectal area, which are necessary to push the feces out through the small opening of the cloaca. The pressure generated by penguins has been estimated to be anywhere from 10 to 60 kilopascal, significantly higher than the average human.

Despite these discoveries, there are still some mysteries surrounding penguin feces. One question that remains unresolved is why the streaks of feces radiate out from the nest in all directions with no noticeable preference. Is this behavior dependent on wind direction, or do penguins somehow choose to fling their feces in specific directions? These are questions that future research may be able to answer.

To address this issue, the Japanese researchers conducted their own study on the projectile trajectory of penguin feces. They observed and recorded the behavior of chinstrap and Adélie penguins at a breeding site in Antarctica, measuring the angle at which the feces were released and the distance they traveled from the nest.

Their findings showed that the angle of ejection varied significantly depending on the surroundings and the position of the penguin. In some cases, the feces were released at a steep angle and traveled a longer distance than predicted by the original 2003 study. The researchers concluded that the projectile trajectory of penguin feces must be taken into account when calculating the pressure generated by these birds during defecation.

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