If I asked you to imagine a penguin, chances are you’re thinking about the classic black and white tuxedo look of a penguin, maybe with a splash of orange or yellow, but little penguins break that dress code. With vibrant, beautiful blue back feathers that contrast sharply with the bright white of the belly, they cut a striking figure, despite standing only 30 cm tall. Those blue feathers are unusual, not only among penguins, but among all other species.
Colour in nature can be caused in two ways, through pigmentation, and through physical structures. In pigmentation, chemical pigments absorb certain wavelengths and reflect a single colour. In physical structures, the tiny nanostructure of the object scatters and refracts light, resulting in a colour that changes slightly depending on the angle you view it.
With little penguins, their vibrant blue comes from this microscopic architecture in the feather tips. What makes them even more remarkable is that these specific structures haven’t been seen in any other animal.
This unique structure is formed by beta-keratin nanofibers. Beta-keratin is a protein that provides structure to a specific cell, think the scaffolding holding everything in place. This specific protein is frequently found in tough body parts; scales, claws and feathers, and adds rigidity and sometimes, a waterproof quality to the structure, which is perfect for the frequent diving behaviour of little penguins! This protein creates tiny structures, referred to as nanofibers. To provide some scale, a single human hair is approximately 90,000 nanometers wide. These structures are folded and arranged in such a way that creates pockets of air and scatters light, reflecting a colour back. In little penguins, the result is a vivid blue that is created by the very structure of the feathers. And it’s a blueprint that no other species seems to share!
So next time you’re admiring the beautiful, indigo blue of a little penguin’s feathers, stop for a moment and admire the unique nanostructure held within those feathers that have been millions of years in the making.