As slimming as a penguin's tuxedo-like markings are, some of them do have a tendency to gain weight. And with good reason. Male king penguins spend up to a month fasting, and have to eat enough before that to survive and keep their baby penguins safe and fed.

While the additional weight (fish belly?) might be less noticeable in the water, once the penguins are on land, they have to figure out how to deal with the newly-acquired belly fat. Scientists noticed through observations that it seemed like the heavier penguins were falling down more often, but they wanted to figure out why. Were they walking differently?

In a paper published in PLOS One Astrid Willener and colleagues describe how the addition of weight affects how King penguins walk on land. Naturally, to measure this, they needed a penguin-sized treadmill.

No, really. Take a look: