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the range of water or milk or anything
else a cat would likely lap, the researchers say. Instead the main factors were the
inertia of the rising liquid and gravity.
The tug-of-war between inertia and
gravity dictates many natural movements involving fluids, from the way a
duck swims to the Jesus lizard’s ability
to sprint short distances over water. The
relationship between the two forces is
characterized by a quantity known as
the Froude number. In the case of feline
lapping the Froude number is near 1,
indicating that inertia and gravity are
roughly in balance in the water column
pulled up by a cat’s tongue.
A gray house cat named Cutta Cutta
inspired the study and served as its
primary participant. But researchers
analyzed lapping motions in other felines
as well by videotaping zoo animals and
looking at the fine selection of videos on
You Tube that depict cats drinking. The
researchers noted that lions lap more
slowly than house cats do, and showed
that drinking pace is related to body
weight in a similar way for all the species
to get a sip of milk, a cat curls the tip of its tongue into a J shape (top center) and
touches it to the surface of the liquid (top right), then pulls up a column of liquid
that adheres to the tongue (bottom left). Before the column can collapse under its
own weight, the cat snaps its mouth shut (bottom center) to catch a few drops.
studied. The various cats lick at a pace
that allows them to consume the most
liquid possible in the shortest time.
Studies like the cat analysis offer
insight into basic puzzles of the evolution
of mammalian feeding. “All infant mam-
mals suckle by very similar mechanisms,
yet there is tremendous variation in adult
drinking mechanisms,” German says.
Also, understanding nature’s diverse
drinking strategies may inspire help for
the many people who struggle to swallow.
Back Story | stopping time
researchers have used high-speed photography to investigate the details of animal motion since the 1870s, when
photographer eadweard muybridge teamed with industrialist and stanford university founder leland stanford to
demonstrate that galloping horses lift all four hooves off
the ground. muybridge set up a series of cameras to photograph a horse at 0.04-second intervals as it ran along
a track, showing that all four hooves do in fact leave the
ground simultaneously (top)—but not as many artists had
imagined. a painting (bottom) by the english artist george
stubbs (1724–1806) depicts a horse with its legs splayed
out in a configuration that would be possible only if the animal hopped along like a rabbit.
in the 20th century, photographic studies by researchers such as mit professor harold edgerton revealed the
mechanics of human motion and the flight of bats and birds.
more recent studies have harnessed high-speed cameras
and pulsing lasers to show how hummingbirds can hover
over an open flower by using a few aerodynamic tricks also
employed by insects.