By Ed Yong
In
the penguin exhibit at the London Zoo, there is a small V.I.P. section,
cordoned off with low boulders, where paying guests can meet the birds
and pose for selfies. On a recent chilly Friday morning, John Hutchinson, of London’s Royal Veterinary College, and James Proffitt,
of the University of Texas at Austin, ventured into the area with other
plans. The biologists set up a kind of corridor, a long wooden platform
with Lucite walls, and began fitting it with metal force plates—two
small, about the width and length of a shoebox, and one large, about
three times bigger. “They’re like fancy 3-D bathroom scales,” Hutchinson
told me, designed to measure force side to side, front to back, and
downward.
Proffitt studies fossil penguins, of which there are a surprising number. The oldest ones, of the stubby-legged genus Waimanu, walked the shores of New Zealand about sixty-two million years ago.
Palaeeudyptes klekowskii, the “colossus penguin” of the Late Eocene, stood just over five feet tall and could have pecked you in the eye. Inkayacu paracasensis, which lived in Peru around the same time, had feathers of gray and auburn, a fact that scientists have deduced from its extraordinarily well-preserved petrified remains. Many prehistoric penguins, in fact, fossilized nicely: they tended to die near coastlines, often sinking into the sediment on the ocean floor, and they were solidly built, unlike their hollow-boned flying contemporaries. This physical robustness was a product of how they evolved. The same extinction event that wiped out most of the dinosaurs also emptied the seas of giant reptiles and many sharks; some of the surviving dinosaurs—the birds—dove into the competition-free waters. They became flightless. Their skeletons became thicker. Their wing bones shortened and flattened, eventually becoming streamlined flippers. Their breastbones became enormous, anchoring the huge muscles that were needed to power an underwater flapping stroke.
Their ankles became grotesquely short and compact—“almost elephantine,” Hutchinson said—and their postures shifted from horizontal to upright. And, somewhere along the line, they started to waddle.
The waddle is endearing, yes, but it also looks inefficient. If you asked a modern penguin to walk ten feet, it would burn twice as many calories doing so as another animal of similar size. Scientists figured that the waddle was to blame, but in 2000 the biologists Timothy Griffin, of the University of California, Berkeley, and Rodger Kram, of the University of Colorado, Boulder, published a study that proved otherwise. They persuaded five emperor penguins to walk over a force plate and found, to their surprise, that the birds are not wastrels but, rather, relative paragons of economy. As a penguin rocks to one side, it stores the kinetic energy of its swing as potential energy, which it then uses to power its next step. In this way, it recovers eighty per cent of the energy that it expends on each stride, one of the highest values reported for any animal. Why, then, the apparent inefficiency? In their study, Griffin and Kram blamed the short legs. Penguins must take smaller, quicker strides than other birds of the same weight, which requires the calorie-intensive use of fast-twitch muscle fibres. Their gait compensates for their physiological shortcoming. If they didn’t waddle, they would be even more inefficient than they already are.
Hutchinson, who is one of Kram’s protégés, planned to use similar methods for the London Zoo experiment. He is a veteran of such studies, having measured the walks of cranes, elephants, emus, giraffes, leopards, ostriches, rhinos, and tigers; his lab is outfitted with force plates in many sizes, from tiny ones for salamanders to huge ones for horses. In the penguin corridor, the combination of plates and camera would allow Hutchinson and Proffitt to discern the position of the animals’ legs, the force of their footfalls, and their posture as they moved. “Once we tease apart those three factors in living penguins, we can trace them back through the fossil record,” Hutchinson said. Proffitt had already created several skeletal reconstructions by putting fossils in medical scanners. Hutchinson planned to dissect some frozen specimens given to him by London’s Natural History Museum, using what he learned of modern penguin anatomy to add virtual flesh to Proffitt’s models. Their ultimate goal was to take the digital penguins for a walk—assuming that they could get the real ones through the corridor.
The first penguin approached. With an agility that belied its bumbling demeanor, it leaped straight over the smaller force plates. The second penguin seemed more circumspect, pausing at length to examine the unfamiliar terrain. Matyasova lured it on with sprat, but a third penguin blundered forward, joining it on the large force plate—a four-footed, two-penguin chimera. Matyasova then tried putting a penguin directly on the plate: it stood still and pecked at the duct tape holding the corridor together. Fortunately, this was just a dry run, though it was clear that Hutchinson’s patience was being tested as much as his equipment. “It almost always takes a while for the animals to get used to what you want them to do,” he said. “They’ll get progressively more coöperative.”
Hutchinson and Proffitt went back every morning for the next week to collect data. By Thursday, when I met them again, things were looking up. The penguins had acclimated to the corridor. As they walked through it, Hutchinson cheered them on and Matyasova called out their names: Pickle, Summer, Harlequin, Carnaby, Dingle. Even Ricky the rockhopper, with his stocky body and unruly yellow eyebrows, turned up. “Data’s coming thick and fast,” Hutchinson said. Lines of force streamed across his laptop screen in red and green.
The biggest challenge now was keeping the penguins interested. Matyasova used props to entice them. A tatty peacock feather proved popular, but one of the penguins made off with it, so she switched to a tennis ball on a stick. The older penguins soon became bored—breeding season was nearing, and they got busy collecting twigs for their nests—but nine youngsters, which were raised in the zoo, were still going strong. The eldest of them, Puddle, was reared alone, and, perhaps as a result, was prone to acting out. He pecked at the equipment, tried to eat Matyasova’s boots, and generally got in the way. “If there’s a naughty penguin around, I assume it’s Puddle,” Hutchinson said. Puddle’s comrade Lenny—who, though female, is named for Len Goodman, a male judge on “Dancing with the Stars”—was far more agreeable. She raced over the plates again and again. “This paper’s just going to be ‘The Biomechanics of Lenny,’ ” Hutchinson said.
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