|Title||Hidden keys to survival: the type, density, pattern and functional role of emperor penguin body feathers|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Williams C.L, Hagelin J.C, Kooyman G.L|
|Journal||Proceedings of the Royal Society B-Biological Sciences|
|Type of Article||Article|
|Keywords||antarctica; behavior; chicks; dives; Emperor penguin; feather density; feathers; heat-transfer; insulation; mechanical-properties; penguin; ross sea|
Antarctic penguins survive some of the harshest conditions on the planet. Emperor penguins breed on the sea ice where temperatures drop below -40 degrees C and forage in -1.8 degrees C waters. Their ability to maintain 38 degrees C body temperature in these conditions is due in large part to their feathered coat. Penguins have been reported to have the highest contour feather density of any bird, and both filoplumes and plumules (downy feathers) are reported absent in penguins. In studies modelling the heat transfer properties and the potential biomimetic applications of penguin plumage design, the insulative properties of penguin plumage have been attributed to the single afterfeather attached to contour feathers. This attribution of the afterfeather as the sole insulation component has been repeated in subsequent studies. Our results demonstrate the presence of both plumules and filoplumes in the penguin body plumage. The downy plumules are four times denser than afterfeathers and play a key, previously overlooked role in penguin survival. Our study also does not support the report that emperor penguins have the highest contour feather density.
"The findings in this study demonstrate that emperor penguins have a much more complex feather distribution than was previously appreciated. Different penguin species inhabit polar to tropical environments, suggesting there must be considerable variation in feather pelage. It has yet to be determined, however, whether other penguins have plumage structures as complex as emperor penguins. While emperor penguin contour feather density is not the highest of any bird, a much greater concentration of plumules provides an additional fourfold layer of insulation, vital for survival during the harsh Antarctic winter. The filoplumes we discovered adjacent to contour feathers may play a similarly important survival role. By signalling the occurrence and location of a displaced feather, filoplumes may be key to maintaining an impermeable exterior, as well as the smooth hydrodynamic shape that probably contributes to a low cost of diving in emperor penguins."