Weasels dance for food; Old glass defies cutting
Q: I have read that weasels sometimes perform a "hypnotic
dance" to mesmerize their prey before attacking them. Any truth to this notion?
J., Kansas City, Missouri
 A
long-tailed weasel. Photo courtesy of the National Park Service.
A: A brown weasel pokes his head out of a burrow, white throat
gleaming in the sun, turns his head this way and that, and spies gray voles nibbling on grass in the meadow. He knows the voles will scatter
when he comes out. So he goes unpredictable.
He leaps straight up, humps his flexible back, bending like a jack-knife
diver, then straightening, dives back in the hole —
in one swift movement almost too fast to follow. He leaps back out, high
into the air, hisses and bounds away from the voles. The voles
watch, fascinated. The weasel doesn't disappoint. He dances back
to the hole, frizzes his tail and dives in, only to leap out, and prance with
sideways leaps
towards the voles, making a chuckling noise.
Still the mouse-like creatures watch. The weasel stops and flips his
back legs straight out, like a bucking bull, and comes down, a little closer. He flips up again, but lands on his back, twists
around, closer. Leaps, and leaps and lands — among them!
Pouncing on a fat vole with his forelegs, he bites the back of the head and
kills.
Predators "can exploit unpredictability to confuse prey, as when weasels do
'crazy dances' to baffle the voles that they stalk," says evolutionary
psychologist
Geoffrey F. Miller, professor at the University of New Mexico.
"The normal method of hunting is to stalk or trail the prey, and then to kill
swiftly with a bite on the back of the victim's head," says the International
Wildlife Encyclopedia. But occasionally their strategy is to take "leave of their senses,
bounding about,
bucking, somersaulting, and so on."
Weasels, burning energy at a fearsome rate, need food, desperately, all the
time. They eat 40% or more of their body mass daily," says biologist
Jim Lieb of the Alaska Department of Fish & Game.
Further Reading:
Protean primates: The evolution of adaptive unpredictability in competition and
courtship, by G. F. Miller (1997). In A. Whiten & R. W. Byrne (Eds.),
Machiavellian Intelligence II: Extensions and evaluations, pp. 312-340.
Cambridge, UK: Cambridge U. Press.
International Wildlife encyclopedia,
edited by Maurice Burton and Robert Burton
Weasel war dance video, (loud) by Spatata and YouTube.com
Weasels,
Alaska Department of Fish & Game
Voles, Alaska Department of Fish & Game
Q: Why can't you cut old glass with a scoring tool? From my
materials education class, glass can be regarded as a super-cooled liquid that is in a
continual state of flow. This would explain why old windowpanes appear to
distort an image, but why can't it be cut? Dave, Aberdeen, England.
Making windowpanes in the 18th Century. Drawing courtesy of London Crown Glass
Company.
A: Actually, you can cut old glass with a scoring tool, but it's tricky,
because old windowpanes are uneven. Your material
education class, however, taught misinformation. Glass is not in a
continual state of flow. That theory has been
disproved,
says Robert
H. Brills, research scientist at the Corning Museum of Glass.
Instead, it's the glass-making process that distorted the glass.
Before the mid 19th century, glassblowers gathered molten glass on the
end of a blowpipe, and blew it into a balloon shape. They transferred the
red-hot balloon to a long, solid rod. Then, while heating the balloon,
a glassworker twirled the rod rapidly until the balloon flattened, and spun out
into a disk. See figure. They cut the disk rim into panes. The glass was thicker toward the outer
rim
edge where the spinning rod flung it.
In the early 20th Century, glassmakers used a process that also resulted in
uneven glass. They poured molten glass on large cooling
tables. The glass was thicker in the center where it was poured.
Then they cut the big sheets into smaller windowpanes, thicker on one end than
the other.
Windowpane installers usually placed the thicker side down for stability.
Occasionally, though, we have found the thinner side down.
That's why old glass is difficult to cut: it's uneven due to a
manufacturing process.
"Additional issues that can make it more difficult to cut and break glass
are how well the glass has been annealed and excessive damage on the surface,"
safety glass consultant
Siegfried Herliczek emails.
I checked the Internet for techniques to successfully score-cut old glass,
and have included them in Further Reading. Here's the one that appealed to
me: "When it comes to old glass, I usually have a local glass shop do the
cutting. They have a very sharp and expensive cutting tool that makes an
unusually deep score mark," says 'TranquilityBase' in a discussion forum.
Further Reading:
Why glass can shatter unexpectedly, WonderQuest
Old glass, Killifish discussion list
Cutting
old glass, Don Wilkins
Window panes from spun hand-blown glass, London Crown Glass Company
(Answered May 7, 2007)
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