Geoscience Reference
In-Depth Information
birds but more solid in others. Bird droppings that are more solid typically wear a
little white cap of liquid uric acid on one end. Prideful car owners everywhere have
experienced such calling cards from songbirds; when flocking, these birds leave an
impressive amount of waste. Nonetheless, raptors and other carnivorous birds are
famous for their white-liquid sprays, which sometimes squirt several meters behind
them from their roosts.
However, probably the most charismatic of avian sprayers are penguins. In a
paper published in 2003, two researchers, Victor Meyer-Rochow and Jozsef Gal,
became intrigued with the radial patterns of feces created by two penguin spe-
cies, chinstrap (
Pygoscelis antarctica
) and Adélie (
Pygoscelis adeliae
), which they
formed by jet-propelled defecating around their ground nests (the penguins, that is,
not the researchers). As a result, the researchers calculated the physics behind these
intriguing traces, taking into account a variety of factors such as: horizontal dis-
tances covered by the spray, poo density, as well as cloacal diameter, shape, and
height above the ground. After making a series of measurements, including pen-
guincloacaldiameters(thatwouldhavebeenfuntowatch),theyfiguredthesefecal
blastsexitedat2.0m(6.6ft)/sec,althougheachvolleyonlytookabout0.4seconds.
Once they figured values for density and viscosity of the liquid, which they unap-
petizingly compared to olive oil, all numbers were plugged into equations, yielding
estimated pressures of 10 to 60 kilopascals. For comparison, a kilopascal is 1% of
normal atmospheric pressure, so 60 kilopascals is more than half an atmosphere,
and much more forceful than what any known human can do. So if someone placed
a defecating penguin's cloaca in front of you, the force generated by its stream
would be only about one-fifth that of a garden hose, albeit with uric acid instead of
water.
Before wading any more deeply into urine orfeces, though, let'stalk about the
other end of the voiding spectrum: puking. As many individuals and human soci-
eties have learned, purging the upper part of an alimentary canal, however discom-
forting it might feel at the time, can be therapeutic. In our species, vomiting mainly
