Beyond thick and beautiful, penguins are efficient, anatomically speaking. Their bodies have several adaptations that allow them to swim gracefully and quickly, and capture prey without much effort. Also, their bright and dense plumage help them withstand the low temperatures of the water in which most species swim.
Penguin weight and height
It depends on the species, obviously. The largest penguin is the Emperor penguin (Aptenodytes forsteri), with a height 1.10 to 1.30 meters, and weighs between 22.7 and 45.4 kilograms. Three times shorter, the Eudyptula minor, or little Penguin, is the smallest species with 30-33 centimeters high and 1.5 kg weight on average. The other species have sizes and weights that lie between these two extremes, the emperor penguin and the little blue penguin.
Anatomy of a king penguin.
Skeleton
Penguins have a bone skeleton. Bones are very hard and thick, unlike other birds that have light skeletons to fly. Since penguins do not fly, they do not need a light, but strong, robust and not filled with air skeleton to help them submerge quickly and to stiffen their fins so they can be moved through the water more efficiently. The bones of their fins are shorter and flatter than in other birds, and many of these bones are fused. The elbow joint and the wrist are almost merged.
The tarsometatarsus, a bone at the bottom of the legs, is the hardest and is highly enduring, even after the penguin dies. Its short length helps reduce friction when swimming, but it also provides support when the bird stays on land.
The bones of their fins are shorter and flatter than in other birds.
Plumage
Their set of feathers, or plumage, forms a dense, durable and protective layer that isolates them from the cold air and icy water penguins usually inhabit, to prevent heat from escaping their body. Penguins are warm-blooded animals, so they need a lot of feathers to keep body heat.
The density of the plumage in the penguin body is 30 to 40 feathers per square centimeter, about three times higher than the feather density of a flying bird. In fact, the emperor penguin is the bird with the largest quantity of feathers. They are arranged randomly in their body, and not aligned in rows, and there is also an air layer near the skin that insulates them from the cold.
Each feather has a soft and a hard part; the first is closest to the body and is partially under the skin. The solid part is visible and has a structure like barbs on either side of the shaft. Additionally, all feathers are attached to a particular muscle that moves them up and down to protect the penguin from cold, analogous to hairs in the skin that get upright when people feel cold.
Feet of a rockhopper penguin.
The plumage color varies with the species. Usually, it shows a smooth and shiny appearance. The predominant colors are black on the back and white on the front, but many exhibit intense yellow and orange hues in the upper chest, head, and beak. The little penguin (Eudyptula minor) has bluish feathers on the head, back and limbs, being a unique case. Penguins of the genus Spheniscus have fleshy pink and featherless areas on the head and black feathers stripes across the chest.
The body shape of all penguins is fusiform, spindle-shaped.
The typical color of penguin plumage, often compared with a men tuxedo, has an important function because of the dark color camouflage them if viewed from above, and improves the solar heat retention. In contrast, their white belly allows them to pass almost unnoticed by predators from below.
External morphology
The body shape of all penguins is fusiform, spindle-shaped: thin at the ends and thicker in the center. Their head tends to be large, small beak, short neck, and elongated body. No visible ears, and their tail, short, is like a wedge but longer in the Chinstrap penguin (Pygoscelis antarcticus), the Adelie penguin (Pygoscelis adeliae) and the Gentoo Penguin (Pygoscelis Papua). Their legs are very short, powerful and webbed to improve swimming efficiency; also, as their position is towards the back part of their body, they can walk upright.
Males and females are similar; sexual dimorphism is almost nonexistent except in the crested penguins, which males tend to be more robust and with longer beaks. Their wings are modified and became fins; because its shape resembles paddles and help them swim and dive nimbly. The beak is usually long and thin in the species that feed mostly on fish but is shorter in krill feeders.
Sources:
https://seaworld.org/en/animal-info/animal-infobooks/penguin/physical-characteristics
https://seaworld.org/en/animal-info/animal-infobooks/penguin/adaptations
Salomon, David. Penguin-Pedia: Photographs and Facts from One Man’s Search for the Penguins of the World. David Salomon, 2012.
https://en.wikipedia.org/wiki/Penguin#Anatomy_and_physiology
http://animaldiversity.org/search/?q=penguins&feature=INFORMATION
www.bioexpedition.com/penguin-anatomy/
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