On numerous occasions in the history of life on Earth, land animals have developed, after lengthy evolution, adaptations that allow them to live in the ocean, an environment rich in food. Among those animals are penguins, dolphins and marine turtles, but also many reptilian groups contemporaneous with dinosaurs.
Why don’t penguins fly?
The adaptation of birds to a marine habitat happened in different ways. Seabirds don’t necessarily need to resemble chubby torpedoes, like penguins, to be able to travel the seas. Some of them, like the albatross and the gannet, are experts at soaring, permitting them to easily cover hundreds of kilometers a day.
So then why don’t penguins fly? They’ve lost their capacity for flight, because short, rigid wings are much more effective for swimming fast and chasing down prey that would otherwise be inaccessible: fish, squid and krill. The advantage they get out of it fully compensates for the loss of flight.
Why must penguins leave the sea to breed?
Quite simply because they lay eggs that are unable to breathe in the water (amniotic eggs). Penguins have to find land surface to be able to lay and incubate their eggs. As suitable terrain is very rare in the middle of the vast southern ocean, penguins have taken to forming large nesting colonies of breeding birds.
Why do penguins have an upright posture?
The penguin could not allow itself, in the course of its evolution, to grow a tail in place of its legs (as was the case with the dolphin), since it has to move about on solid ground. Its legs are moreover very powerful, since the rocky coasts are often steep and swept by strong ocean surges.
Evolution generated the movement of the legs to the posterior end of the body, at the level of the tail, to serve as a “rudder,” while forward movement is ensured by wings transformed into strong flippers.
The result of this singular adaptation is one of the penguin’s most notable features: its upright posture. When they walk, they must absolutely remain vertical in order to keep their center of gravity above their feet.
A side effect of that evolution is our fascination with these birds trotting around in an upright position and looking like little people in white tie and tails.