Penguin Facts
Penguin beginnings
With their streamlined bodies and speed in the water, one could almost be forgiven for mistaking penguins for fish. They are truly built for life in the sea. We don’t really know exactly how penguins came to evolve from the early bird ancestors because palaeontologists have discovered relatively few fossils, so their history still has many gaps. We do know that birds evolved from a reptile ancestor about 150-200 million years ago in the Mesozoic era when dinosaurs still roamed the Earth. However, until recently, scientists have lacked enough evidence to determine when the early bird ancestors evolved into penguins. When naturalists first discovered penguins, they thought that they were related to the flightless auks that live in the high Northern hemisphere. At the time auks were also called “penguino”, meaning “fat present”. They must have tasted good to the travel-hungry sailors to be given such a name.
Icadyptes salasi |
Evidence now suggests that the closest living relatives of penguins are the loons (Gaviiformes), frigatebirds (Pelecaniformes) as well as the albatrosses, shearwaters and petrels (Procellariformes) (Sparks and Soper 1987, del Hoyo, et al., 1992). The albatrosses, shearwaters and petrels are similar to penguins because they all spend considerable time searching the ocean for fish, have similar courting displays, long lifespans and most breed in burrows.
We do know that penguins evolved from flying birds, not the other way around. Penguins have flippers that are paddle-like modifications of a flying bird’s wing. Some of the bones in the flipper are fused together like those in flying birds, which strengthens the wing for the attachment of feather quills. In penguins, however, the flight feather quills have long since been lost. Penguins also have a large breastbone and tail bones (pygostyle) similar to those of flying birds.
Until recently, scientists thought that penguins evolved in cold climates in Antarctica and New Zealand about 10 million years ago. This would have meant that penguins evolved specifically to handle cold and icy conditions. However, in the last few years, scientists have uncovered penguin fossils that are much, much older, that would have lived in one of the warmest periods the Earth has seen over the last 65 million years. Infact, the oldest fossils are from the tropics of Peru and South America, thought to be 42-36 million years old (mid-late Eocene) (Williams, 1995). The largest fossil found was a towering penguin 1.5m tall called Icadyptes salasi. It would have reached a man’s shoulders and it hada long pointed beak (17.5cm) for spearing prey. Other large penguin fossils found in New Zealand are thought to have lived in estuaries when the earth was much warmer. Infact, scientists now believe that the origins of penguins began evolving during the Cretaceous period, 65 million years ago, so it seems their beginnings are quite ancient.
Why do penguins only live in the Southern hemisphere?
We know that flightless seabirds did once live in the oceans of the northern hemisphere, and they looked a lot like penguins but infact they were related to pelicans. The now extinct Plotopterids looked just like long necked penguins, and they also had dense bones and stiff elbows like penguins. The Plotopterids, however, died out about 25 million years ago when sea lions moved into the same territory.
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In the south, where penguin ancestors first lived, the warm climate allowed a large number of species to evolve. Eventually the world became colder and colder and Antarctica became more isolated as the Antarctic Circumpolar Current formed. The large ancient penguins that we now see in the fossil record probably couldn’t adapt to the cold as food became scarce. At this time, the number of prehistoric seals and small whales began increasing, so these penguins may have either been out-competed for food or eaten as prey themselves. So we now have fewer species of penguins, only 17, and most of them are much smaller than the large ones that used to swim about the Earth millions of years ago. Because the penguins we see today, survived and evolved through the cold times, they are adapted to the cold climates of Antarctica and temperate oceans, so this is most likely why they have not crossed the warm tropics into the Northern hemisphere.
One of the reasons we know so little about penguin ancestors is that many of the fossils have yet to be found, particularly in Antarctica, as they are likely to still be under thick layers of ice.
A variety of tuxedos
There are 17 species of penguin, ranging from the frozen Antarctic, to the Galapagos Islands on the equator. Penguins are the most successful avian predators of the Southern Oceans. They can run as fast as most men, and swim faster than most fish. They are perfectly adapted to a half-life between land and sea. Penguins range from the tiny little penguin only 30 cm high to the Emperor penguin, about 1m high. They all wear tuxedos of black or blue and white, some with orange or yellow bow-ties, crests or ear-muffs.
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How are they adapted to living in the sea?
Penguins have many ways of dealing with the cold, dangerous and expansive ocean. Firstly they are remarkably waterproof which is due to thousands of tiny feathers, that all overlap to provide a waterproof cover which is sealed with a waxy substance from the preen gland or uropygial gland. The bottom of each tiny feather has a downy, fluffy appearance, which helps to trap a layer of air around the penguin’s skin. This layer of air helps to keep the penguin warm and dry.
The blood vessels, known as the arteries and veins, in their flippers and feet are very close together so that heat can be exchanged. The blood vessels carrying blood from the warm heart to the flippers run next to the blood vessels that carry cold blood from the very thin flippers towards the heart. This system, known as the “countercurrent” system, allows the warm vessels to heat the vessels carrying cold blood before it reaches the heart. This can work in the opposite way if a penguin sitting on a sunny Australian beach is too hot, the warm blood from inside the body can be cooled by the blood returning from the feel and flippers that have been cooling in the breeze. Penguins also pant like dogs because they have no sweat glands to help them cool down. Other penguins like the emperor penguin have more of a problem staying warm through wintry blizzards on the ice, so they prefer huddling and sitting on their fat heels with their toes in the air to avoid touching too much ice.
Unlike most other birds penguins have solid bones, which are stronger and heavier. The air that is trapped under their feathers makes them float high in the water, but if they had hollow bones like flying birds, they would have trouble diving.
Penguins are expert fishermen, catching fish and squid with their powerful bills and swallowing the slippery prey whole with the help of a spiny tongue.
How do they manage to avoid hungry hunters?
Penguins have many natural predators out at sea, including leopard seals, killer whales and fur seals. To avoid the jaws of these hungry kings of the sea, penguins have speed and excellent swimming abilities on their side. They can swim up to 7-10km/hr and they use less energy to swim than to walk on land. Even when they dive deeply, their heart beats more slowly so they use less energy and can therefore stay underwater for longer. Adelie and Gentoo penguins, that live in Antarctica normally have hearts that beat 80 to100 times each minute, similar to our hearts, but during deep dives, these penguins slow to only 20 beats per minute (Muller-Schwarze, 1984). They are fantastic divers, especially the Emperor penguins, which can hold their breath for 18 minutes and dive to an incredible 500m deep.
Penguins have torpedo shaped bodies and long flippers to fly through the water. They can use their tails, bills and webbed feet to quickly change direction. They can also leap out of the water, known as porpoising, sometimes changing direction whilst in the air to confuse predators.