Vincent, Sahinkaya, and O’Shea examined a green woodpecker (Picus viridis) that was in the terminal state known as ‘road kill’. They measured the remains using old-fashioned methods and also with X-ray equipment, thus determining the values for several parameters: head mass, body mass, and the relative lengths of the parts. Using these, and also video of a living, pecking woodpecker of similar size, the scientists estimated the bird’s head inertia, body inertia, neck stiffness, neck damping, and body spring stiffness. They wrote equations to describe a woodpecker’s motions as it moves through all phases of the drum-drum-drum-on-wood cycle. To keep the mathematics fairly simple, there were a few engineering simplifications. The woodpecker’s vertebrae and neck tendons together behave as a spring. The tree is, essentially, a stiff spring with a damper.
X-ray of a road-kill green woodpecker (top); schematic of woodpecker at work (bottom)
The study proudly proclaims an intended payoff from this research: ‘One of the reasons for studying the woodpecker was to derive a design for a lightweight hammer. It was reasoned that the woodpecker is a bird, therefore has to fly and therefore is constructed as light as possible. The mechanism, which has emerged as a result of the model reported here – momentum transfer from body to head of the woodpecker – has been used in the design of a novel hammer [in which a] rotating crank is connected by means of a rod to the casing, so that the motor plus its mounting oscillates about a central pin.’
Vincent, Sahinkaya, and O’Shea say their original intent was to use this hammer in space exploration, ‘where it has no net inertia until it comes in contact with an object’. But its first use, they confide, probably will be in dentistry.
Vincent, Julian F. V., Mehmet Necip Sahinkaya, and W. O’Shea (2007). ‘A Woodpecker Hammer.’ Proceedings of the Institution of Mechanical Engineers, Part C, Journal of Mechanical Engineering Science 221 (10): 1141–7.
The Physics of Skulking and Falling Cats
Cats may skulk, and cats may fall – but no matter what they do, cats must obey the laws of physics. Scientists have tried repeatedly to figure out how they manage to do it.
At the extreme, physicists analysed what happens to a dropped cat. That’s a cat in free-fall, a cat hurtling earthwards with nothing but kitty cunning to keep it from crashing.
In 1969, T. R. Kane and M. P. Scher of Stanford University published their monograph ‘A Dynamical Explanation of the Falling Cat Phenomenon’. It remains one of the few studies about cats ever published in the International Journal of Solids and Structures. Kane and Scher explain: ‘It is well known that falling cats usually land on their feet and, moreover, that they can manage to do so even if released from complete rest while upside-down … numerous attempts have been made to discover a relatively simple mechanical system whose motion, when proceeding in accordance with the laws of dynamics, possesses the salient features of the motion of the falling cat. The present paper constitutes such an attempt.’
And what an attempt it is!
Kane and Scher neither lifted nor dropped a single cat. Instead, they created a mathematical abstraction of a cat: two imaginary cylinder-like chunks, joined at a single point so the parts could (as with a feline spine) bend, but not twist. When they used a computer to plot the theoretical bendings of this theoretical falling chunky-cat, the motions resembled what they saw in old photographs of an actual falling cat. They conclude that their theory ‘explains the phenomenon under consideration’.
In 1993, a professor at the University of California, Santa Cruz, applied some heavier-duty mathematics and physics tools to the same question. Richard Montgomery’s study, called ‘Gauge Theory of the Falling Cat’, leaps and bends across twenty-six pages of a mathematics journal. Then it mutters that ‘the original solutions of Kane and Scher [are] both the optimal and the simplest solutions’.
But cats rarely fall from the sky. More commonly, they skulk. On the ground. And skulking cats are just as provocative, to a physics-minded scientist, as plummeting cats.
In 2008, Kristin Bishop of the University of California, Davis, together with Anita Pai and Daniel Schmitt of Duke University in North Carolina, published a report called ‘Whole Body Mechanics of Stealthy Walking in Cats’, in the journal PLoS One.
They studied six cats, three of which ‘were partially shaved and marked with contrasting, non-toxic paint to aid in kinematic analysis’. They discovered ‘a previously unrecognised mechanical relationship’ between ‘crouched postures’, ‘changes in footfall pattern’, and the amount of energy needed to produce those crouched-posture footfall patterns.
Cats that intend to skulk, in Bishop, Pai, and Schmitt’s view, are hemmed in by the laws of the physical universe. They must make ‘a tradeoff between stealthy walking’, which uses a lot of energy, and plain old, energy-efficient cat-walking.
Kane, T. R., and M. P. Scher (1969). ‘A Dynamical Explanation of the Falling Cat Phenomenon.’ International Journal of Solids and Structures 5: 663–70.
Montgomery, Richard (1993). ‘Gauge Theory of the Falling Cat.’ Fields Institute Communications 1: 193–218.
Bishop, Kristin L., Anita K. Pai, and Daniel Schmitt (2008). ‘Whole Body Mechanics of Stealthy Walking in Cats.’ PLoS One 3 (11): e3808.
Three
Dogs, Cows, Cats,
and So Forth
In Brief
‘The Cow with Zits’
by Walter J. Pories (published in Current Surgery, 2001)
Some of what’s in this chapter: Frightening a cow in the forties • Motivating the domestic fowl • Yawning contagiously, or not, with fellow tortoises • Lying down and standing up, lying down and standing up, and mooing • Following Fish on fish, and Fish on trees • Roaring with or without a Klipsch Heresy Speaker placed two hundred metres away in the jungle • Bollocks for dogs; rolls for kitties • Collecting lizards from the sky • Towing and showing naked Russian swimmers in place of dolphins • Macaque upchuck
Cattle Rustling
What can be learned with a cat, a cow, and a paper bag? This is not a moot question. To raise dairy cows can be intellectually challenging, in addition to being hard physical work. Every dairy farmer knows this, although it may be news to a small number of milk-guzzling, cheese-chomping city dwellers.
Fordyce Ely and W. E. Petersen wanted to understand why some cows spew their milk. This was in the early 1940s. Much of the world was at war, which may explain why Ely and Petersen’s report, titled ‘Factors Involved in the Ejection of Milk’, made only a little splash when it was published in 1941 in the Journal of Dairy Science. Ely was based at the Kentucky Agricultural Experiment Station, and Petersen at a similar institute in Minnesota. Together they made history, using the aforementioned items – a cat, a cow, and a paper bag.
Ely and Petersen set out to address a nagging dilemma. ‘Cows which habitually “let down” or “hold up” their milk are common in all herds. Several theories have been advanced to explain the physiological processes involved, but each has been found at fault in some regard.’
In search of the truth, they conducted an experiment. The details deal with complex aspects of the nervous system as it relates to the physiology of bovine udders, but I will concentrate here on just one aspect. Here is the pertinent passage from Ely and Petersen’s report: ‘It was thought that there might be a difference in the response of the two halves of the udder as measured by the rate of ejection of milk if the cow was severely frightened. Accordingly, [the cow] was systematically frightened as the mechanical milker was attached. Frightening at first consisted in placing a cat on the cow’s back and exploding paper bags every ten seconds for two minutes. Later the cat was dispensed with as unnecessary.’ So far as I have been able to determine, this experiment was conducted only that one time.
Other scientists tried to startle human beings. Often, they succeeded.
D. N. May of the University of Southampton, UK, carried out one such experiment. In a 1971 report, he writes, ‘[My] result
contradicts a previous finding with animals and suggests that sonic booms are likely to be more startling in quiet environments than noisy ones.’
Not long afterwards, J. S. Lukas at the Stanford Research Institute exposed some sleeping Californians to recorded aircraft sounds and simulated sonic booms. He found that anyone over the age of eight is likely to notice.
Meanwhile, researchers at the Karolinska Institute in Stockholm used real jet planes to produce real sonic booms. They discovered that when you do this at 4 a.m., it awakens the majority of Swedish adults.
Ely, Fordyce, and W. E. Petersen (1941). ‘Factors Involved in the Ejection of Milk.’ Journal of Dairy Science 3: 211–23.
May, D. N. (1971). ‘Startle in the Presence of Background Noise.’ Journal of Sound and Vibration 17 (1): 77–78.
Lukas, Jerome. S. (1972). ‘Awakening Effects of Simulated Sonic Booms and Aircraft Noise on Men and Women.’ Journal of Sound and Vibration 20 (4): 457–66.
Rylander, R., S. Sörensen, and K. Berglund (1972). ‘Sonic Boom Effects on Sleep: A Field Experiment on Military and Civilian Populations.’ Journal of Sound and Vibration 24 (1): 41–50.
Magnetic Chickens
Progress comes slowly on the question ‘Why does the chicken cross the road?’ But come it does. The answers (for there seem to be many) strut in jerkily, from different directions. A new study explains that magnetic fields play some sort of role, at least sometimes, in chickens’ decisions to navigate hither or yon.
The study has a title that seems swiped from a children’s book: ‘The Magnetic Compass of Domestic Chickens, Gallus gallus’. Published in the Journal of Experimental Biology, a venue that generally does not cater to youngsters, it adds flesh and feathers to the sketchy picture revealed in an earlier report entitled ‘Chickens Orient Using a Magnetic Compass’.
Many cultures wonder about the chicken navigation mystery. Fittingly, the ‘magnetic compass’ research team is international. Its members – Wolfgang Wiltschko, Rafael Freire, Ursula Munro, Thorsten Ritz, Lesley Rogers, Peter Thalau, and Roswitha Wiltschko – work, variously, in Germany, at J. W. Goethe-Universität Frankfurt; in Australia at the University of New England in Armidale and at the University of Technology, Sydney; and in the US, at the University of California, Irvine.
They conducted the experiments all in a single land: Australia. The chickens, which were domestic to that nation, had to track down a red ball that had been shown to them but was then moved. The scientists generated a magnetic field that, they hoped, would monkey with the chickens’ orientation. The chickens, in their quest for the red ball, acted as if they were under the influence of a monkeyed-with magnetic field.
Thus the scientists’ conclusion: magnetic fields matter to chickens. This presumably is true of chickens elsewhere, although the report is not explicit on the point.
What do magnetic fields do for the chicken? They ‘facilitate orientation within the home range’, say the researchers. In more specific terms: ‘Tests in magnetic fields with different intensities revealed a functional window around the intensity of the local geomagnetic field, with this window extending further towards lower than higher intensities.’
What the report hints, but does not quite say, is that chickens don’t seem to rely heavily on magnetism. Are the chickens capable of more, for instance, of making more intelligent use of what they perceive? Has our (and to some extent their) civilization withered the birds’ reliance on the Earth’s magnetosphere? The report is mum on these questions.
The traditional question of why a chicken crosses a road stands, at best, partially answered. Perhaps the most likely to solve it is Professor Ian J. H. Duncan, formerly of the Poultry Research Centre in Edinburgh, and now chair in animal welfare at the department of animal and poultry science at the University of Guelph, in Canada.
In 1986, Duncan and a colleague presented a paper at the winter meeting of the Society for Veterinary Ethology, in London. The title: ‘Some Investigations into Motivation in the Domestic Fowl’.
Duncan appears to be methodical about his scratchings into fowl motivation. In 2000 he co-authored ‘Working for a Dustbath: Are Hens Increasing Pleasure Rather than Reducing Suffering?’ Pullet-road-crossing enthusiasts can hope that one day Duncan will confront, directly, the question of questions.
Wiltschko, Wolfgang, Rafael Freire, Ursula Munro, Thorsten Ritz, Lesley Rogers, Peter Thalau, and Roswitha Wiltschko (2007). ‘The Magnetic Compass of Domestic Chickens, Gallus gallus.’ Journal of Experimental Biology, 210 (13): 2300–10.
Freire, Rafael, Ursula H. Munro, Lesley J. Rogers, Roswitha Wiltschko, and Wolfgang Wiltschko (2005). ‘Chickens Orient Using a Magnetic Compass.’ Current Biology, 15 (16): R620–21.
Duncan, Ian J. H., and V. G. Kite (1986). ‘Some Investigations into Motivation in the Domestic Fowl.’ Applied Animal Behaviour Science 18 (3–4): 387–88.
Widowski, Tina M., and Ian J. H. Duncan (2000). ‘Working for a Dustbath: Are Hens Increasing Pleasure Rather than Reducing Suffering?’ Applied Animal Behaviour Science 68 (1): 39–53.
Contagious Yawning in the Red-Footed Tortoise
Scientists know a bit more about contagious yawning – one of science’s utter mysteries – thanks to a study called ‘No Evidence of Contagious Yawning in the Red-Footed Tortoise Geochelone carbonaria’. The study’s authors say their experiments, conducted with seven tortoises, might help eliminate some of the many competing theories as to why humans yawn when they see other humans yawn.
Writing in the journal Current Zoology, Anna Wilkinson, Isabella Mand, and Ludwig Huber of the University of Vienna, Austria, and Natalie Sebanz of Radboud University in the Netherlands, share their hopes: ‘This study aimed to discriminate between the possible mechanisms controlling contagious yawning by asking whether contagious yawning is present in a species that is unlikely to show empathy or nonconscious mimicry: the red-footed tortoise Geochelone carbonaria.’
The researchers say that although tortoises have not been known (by humans) to empathize with or mimic each other, the animals do sometimes respond to things they see around them. That makes the tortoises ‘ideal subjects for examining this question’.
The tortoises, whose names are Alexandra, Moses, Aldous, Wilhelmina, Quinn, Esme, and Molly, were old hands at being scientific test subjects. The study notes: ‘None of the tortoises were experimentally naïve, but they had never previously been involved in a contagious yawning task or any similar experiment.’
The researchers trained Alexandra to open her mouth whenever they waved a little red square near her head. ‘This took 6 months’, they write, and ‘the resulting behavior appeared highly similar to a naturally occurring tortoise yawn ... The yawn is extremely clear and cannot be mistaken for another behavior.’ Alexandra thus became the ‘demonstrator’, the individual who yawned in plain view of her fellows.
In one experiment, the other tortoises watched as Alexandra yawned a single time. In a second experiment, Alexandra yawned several times in rapid (for a tortoise) succession. In the third and final experiment, the observer tortoises watched videos of a tortoise (a) yawning and (b) not yawning. After reviewing the evidence, the scientists determined that there is ‘the suggestion that tortoises do not yawn in a contagious manner’.
The monograph ends with a statement expressing gratitude to their colleagues. Perhaps lacking for warmth, it says, ‘Acknowledgements: The authors would like to thank the cold-blooded cognition group at the University of Vienna for their helpful comments.’
The team’s slow, careful attention to tortoise yawns led to glory of a sort. Wilkinson, Mand, Huber, and Sebanz were awarded the 2010 Ig Nobel Prize in physiology.
Other scientists have experimented with contagious yawning in other species. I will mention just one: ‘Some Comparative Aspects of Yawning in Betta splendens, Homo sapiens, Panthera leo, and Papio sphinx’ by Ronald Baenninger of Temple University in Philadelphia.
‘In this report’, Baenninger writes, ‘I des
cribe observations of yawning by a fish [Siamese fighting fish], by a carnivore [a lion], and by two primate species [mandrills and humans].’ The humans watched ‘a semiprofessional actor read a passage from Alice in Wonderland (the mock turtle’s story)’. The other animals watched nonprofessional non-actors of their own species.
As a final note, I first learned of the tortoise-yawning study from Stefano Ghirlanda, himself a 2003 Ig Nobel Prize winner in the category of ‘interdisciplinary research’ for the study ‘Chickens Prefer Beautiful Humans’. The title of his study is, to some extent, self-explanatory and, to some extent, probably not.
Wilkinson, Anna, Natalie Sebanz, Isabella Mand, and Ludwig Huber (2011). ‘No Evidence of Contagious Yawning in the Red-Footed Tortoise Geochelone carbonaria.’ Current Zoology 57 (4): 477–84.
Baenninger, Ronald (1987). ‘Some Comparative Aspects of Yawning in Betta splendens, Homo sapiens, Panthera leo, and Papio sphinx.’ Journal of Comparative Psychology 101 (4) 349–54.
Ghirlanda, Stefano, Liselotte Jansson, and Magnus Enquist (2002). ‘Chickens Prefer Beautiful Humans.’ Human Nature 13 (3): 383–89.
May We Recommend
‘Determining the Smallest Migratory Bird Native to Britain Able to Carry a Coconut’
by Robert Hopton, Steph Jinks, and Tom Glossop (published in the Journal of Physics Special Topics, 2010)
This report pertains to King Arthur’s postulation in the film Monty Python and the Holy Grail that a migratory bird could have transported coconuts from the tropics to Britain. Hopton, Jinks, and Glossop calculate that the only British bird with a chance at succeeding is the white stork. No go, they warn. The stork’s cross-sectional area is slightly too low to provide the required amount of lift. The stork would fall short, and King Arthur would be nutless.
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