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published on 25 April 2018 in life

Free divers in evening suits

They waddle along in an ungainly and comic way, sliding at speed with their bellies on the ice and swimming even more swiftly in the sea using their wings as flippers. We are talking about penguins, animals that symbolise the Antarctic and life above and below ice, now threatened by climate changes, loss of habitat, over-fishing and pollution. The World Penguin Day, celebrated each year on 25 April, was set up to raise awareness of the risks that penguins are currently facing.
Let’s look together at some curious facts about these animals.
Penguins’ lives
Penguins belong to the order of Sphenisciformes, which includes only one family (Spheniscidae) with 6 genera and 17 species found almost exclusively in the Southern Hemisphere, especially in the southern part of the oceans. Contrary to common belief, penguins do not live only in cold areas. There are, in fact, a number of species that can be found in temperate climates and there is even one species, the Galapagos penguin which, as its name suggests, lives in the Galapagos Islands, close to the equator.

Galapagos Penguin

They are flightless birds that have adapted to the marine ecosystem. In the sea, in fact, they seek the food on which they live: shellfish, squid, fish and krill. However, they return to dry land to reproduce. They move clumsily on land due to the shape of their bodies, which forces them to keep their weight on the back part of their legs, counterbalancing movements with their open wings. On the contrary, when in the water they are exceptionally hydrodynamic!
They are warm-blooded animals, with a body temperature of 37-38 degrees centigrade. A thick layer of fat and their plumage keeps their temperature constant. Penguin plumage forms a dense elastic mesh that keeps a layer of air nect to their skin, increasing their heat insulation and protecting them from water too. It is a kind of “waterproof wetsuit” that protects them from the cold!
They are able to drink salt water because their organisms are equipped with special glands that can eliminate salt from their blood. We human beings do not have this kind of gland – if we drink seawater, the salt makes us increasingly thirsty.

Penguins in evening suits
Not everyone knows that penguins’ elegant plumage, which remind us of a man’s evening suit (a dinner jacket, for some), is not at all an accident, but has a mimetic purpose to ensure that they are not captured by predators while swimming in the sea. It is a kind of colouring that is quite common in other aquatic animals too, such as fish and cetaceans, and it is advantageous when swimming, because it makes them less visible both from above and below. Indeed, when a predator seeks prey from the ocean floor, it will find it difficult to see the white belly of a penguin against the bright surface of the water. If on the contrary, it is hunting from the surface towards the bottom, penguins’ dark backs are difficult to see against the dark depths of the ocean. For this reason, to stay safe, penguins have to wear their black and white evening dress wherever they go!

Skin-diving birds
Penguins are birds but they are unable to fly. Their wings have turned into flippers, their plumage has become a sort of thick, short fur. Within the soft layers of feathers there is a layer of air that allows penguins to float in the water. The layer of air, moreover, together with the thick layer of fat under their skin, insulates penguins in cold waters. Additionally, their streamlined bodies make them expert swimmers. All these characteristics make penguins the birds that are best adapted to swimming and underwater fishing.
These animals spend most of their time underwater looking for food like krill, fish, squid and other small sea animals. When penguins are in the water, they move extremely fast. They use their wings as if they were flippers. Thus, when they are in the water, they flap their wings as if they were flying through the air!

Humboldt Penguin “flying” through the water

Penguin numbers
The largest living penguin is the emperor penguin, which can grow to as much as 122 cm tall and can weigh between 20 and 40 kg. It lives exclusively in one of the most impervious places on our Planet, in the ice and waters surrounding the Antarctic continent and the islands nearby, at latitudes between 66 and 78 degrees south.

Emperor Penguin

The smallest species, on the contrary, is the little blue penguin, which is between 30 and 40 cm tall and weighs between 1 and 2 kg. They live along the southern coast of Australia and in the seas of Tasmania and New Zealand. When it was described for the first time in 1780, the little blue penguin was appropriately given the Greek name Eudyptula minor meaning, significantly, “good little diver”.

Little Blue Penguin. Credits: Wikimedia Commons

Prehistoric penguins were real giants! For examples, the penguins of the Anthropornis genus, now extinct, was as big as humans and, indeed, its name means precisely “man-bird”. These penguins were truly gigantic: they could be as tall as 170 cm and weigh as  much as 90 kg! They lived around 43-47 million years ago, therefore during the late Eocene and the earliest part of the Oligocene, on the land that now forms the Antarctic, New Zealand and Seymour Island.
Penguins’ skill at underwater fishing is proverbial: the Emperor Penguin, for example, swims underwater for as much as 18 minutes and can dive to depths of over 500 m.
Penguins succeed in achieving speeds of 40 km/hour under water: it may not seem much to us, but in reality it is considerable if you consider that the speed of many ships, such as ferries, cruise ships or cargo ships, does not normally exceed 40 km/hour.
Penguins have good hearing. They are able to find a member of their family in a crowd of 80,000 penguins.

By Benedetta Palazzo

 
With the sponsorship of the Italian Ministry of Education, Universities and Research
 
Eni S.p.A. - P.IVA 00905811006