This Penguin on a Treadmill Shows How Waddles Work

Fat penguins have a harder time walking than swimming

J. David Andrews/Masterfile/Corbis

A penguin underwater can pull off acrobatic moves like an ace fighter pilot. Back on land, however, it’s a different story. While their torpedo-shaped bodies might be perfect for swimming around icebergs and dodging hungry seals, walking poses a whole new set of challenges—especially once the pudgy penguins have loaded up on fish, according to a new study.

Wobbly, waddling penguins may be a funny sight, but being able to walk is critical for some species survival. King penguins, for example, trek for several miles inland from Antarctica’s coasts each summer in order to breed, but have no way of hunting for food once they are on their way. In order to prepare for up to a month of fasting, the penguins gobble up as much fish as they can before starting off on their journey, Helen Thompson writes for Science News. But while packing on that extra fat might help them survive mating season, it might also make it harder for the tubbier ones to walk, according to a new study published in the journal PLOS One.

Scientists have observed that fatter penguins fall down more often, but no one was sure exactly why. To figure out what the extra weight was doing to the penguins, a group of biologists from London’s Roehampton University conducted a meme-worthy experiment: making king penguins walk on a treadmill.

“The most difficult and tricky moment is when the treadmill first starts. Once the speed is set the penguins usually walk fluently,” biologist Astrid Willener, who authored the paper, tells Richard Gray for The Daily Mail.

Watching penguins scramble to stay upright on a treadmill might be a funny sight, but it provided some real insights into the mechanics of how penguins walk around after gorging themselves. Using accelerometers, Willener and her colleagues measured the penguins’ gaits and their angle of walking to figure out the difference between how fat and skinny penguins walk.

In the past, studies have shown that obese and pregnant humans change their gait by taking wider stances and shorter steps, but this wasn’t the case with the penguins. Instead, the heavier penguins swayed more from side to side as they walked—the heavier the penguin, the bigger the waddle, David Shultz writes for Science Magazine.

“It is very useful for them to increase their waddle when increasing speed,” Willener tells Gray. “Waddling enables a more stable gait and prevents them from falling over. It also avoids their walk being more costly.”

Because the penguins load up on food to conserve energy for the month they spend helping hatch their chicks, they have to strike a balance between saving enough energy to make it through the summer and being able to outrun predators on land. By waddling and taking more steps, fat penguins put their momentum to good use, Mary Beth Griggs reports for Popular Science.

The experiment might help biologists understand more about how penguins get around during mating season, but it wasn’t without its challenges: namely, getting the penguins to walk on the treadmill in the first place. As Willener tells Gray, training the 10 penguins she and her colleagues studied to walk on the tiny treadmill was one of the most challenging parts of the tests.

“Those that could not walk straight away and were quite difficult to train. Some individuals were lazy and ‘water-ski’ on the treadmill by leaning their back on the wall behind them,” Willener tells Gray.

Luckily for Willener (and for lovers of penguin videos), most of her penguins eventually managed to learn how to waddle in place.

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