It is true that the penguin’s mobility on land is measured by an inelegant waddle. To understand why penguins waddle, you must consider their shape. While the different species do vary in overall size, sport individual bill shapes and bear distinct markings – some of which include color – penguins are all pretty much shaped the same way. Like a torpedo. A torpedo with a relatively large head and two short, wide, three-toed feet. The feet are set back, very close to the tail. This is why penguins stand upright on land.
The waddle effect happens because penguins have a very short stance, or distance between their feet when walking. Imagine having your legs tied together just above your ankles. Then think about walking like that. Better still, have you ever gone to try on a pair of shoes at a big super store like Wal-Mart or Target – where the shoes are tied together? When you attempt to walk in the shoes as you’re trying them out, it’s pretty difficult, right? And you end up sort of rocking side-to-side as you walk. That’s what it’s like for a penguin.