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James Platt

Why Don’t Penguins Fly?

Penguins swimming underwater

Why Don’t Penguins Fly?

by James Platt

Most of the world’s bird species have the capability of flight. In fact, of 11,000 known species of birds, there are only about 60 species including the Common Ostrich (Struthio camelus), Great Spotted Kiwi (Apteryx haastii) and 18 species of penguin that cannot fly at all, which is about 0.5% of all bird species. Why these different species evolved without flight could be due to several reasons; each one will have evolved to fit into a niche within its own environment.

Penguins were originally thought to have evolved separately from flightless birds, until quite recently when fossil records from New Zealand were discovered. These fossils revealed that they had likely descended from the order of Procellariiformes and its closest relatives including the Wandering Albatross (Diomedea exulans) and Antarctic Petrel (Thalassoica antarctica). This could be considered unexpected since the albatross is a bird that travels huge distances in the air. So why would a bird that has massive wings and uses them to glide across continents suddenly evolve into a flightless, chubby penguin?

An albatross flying through the air
Photo credit: Linda Martin

Why did penguins evolve to swim instead of fly?

To understand why they may have evolved in this way, first we must understand flight. Flight in birds is a tricky thing; it is a perfect balance between forces (lift, thrust, gravity and air resistance) that allow the bird to move through the air quickly and efficiently. Birds evolved hollow bones to allow them to be lighter and, therefore, lift off the ground much easier. They also have air sacs built into their body to keep a streamlined aerodynamic body shape that allows them to reduce air resistance. Birds need to stay light because the heavier they are, the more difficult it is to take off from the ground (Tobalske, 2007). In the case of some flightless birds like the ostrich, which weighs over 100kg, its wings would have to be huge to get it off the ground. Instead, they are incredibly fast runners. Similarly, with Emperor Penguins (Aptenodytes forsteri) that can weigh about 25kg, it would take large wings to fly and would not be very energy efficient. So they evolved to “fly” in the water instead. Now some penguin species have branched off and become much smaller and lighter than the Emperor Penguin, such as the Little Penguin (Eudyptula minor) at just 1.5kg, but by this time they were a fully distinct order of birds and had adapted to dominate the water.

An Emperor Penguin tobogganing on the snow
Photo credit: Mike Zupanc

It is believed that the Emperor Penguin is the oldest species of penguin and therefore was the first bird to try to dominate the ocean and land on the continent. But why in such a cold, harsh environment, and why would it become flightless? Well, it’s complicated and there could be many other reasons. There is a total lack of land predators which means they don’t have any immediate threats to fly away from. There is also an abundance of sea life to eat and a lack food resources on land, so they adapted to thrive off the oceans and then live on land, away from their biggest predator, the leopard seal (Hydrurga leptonyx). There are also many benefits to being flightless. Penguins have the opposite to most birds, they have incredibly dense bones that allow them to dive and swim better. Where most birds would have air sacs to stay aerodynamic, penguins can fill some of that extra space with a larger stomach and carry much more food for itself and its offspring — up to a 1/3 of its bodyweight. They can also dive much deeper than flying seabirds they may be in competition with and this allows them to make the most of what their environment has to offer (Alexander, 1999).

Part of the reason penguins swim is because flying is an energy-intensive activity

One more reason they may have lost the ability to fly is that flying is an extremely high energy activity and they need all the energy they can retain to stay warm (Elliott et al, 2013). Most birds use their energy for flying and the bird that is best at conserving its energy is the penguin’s closest relative, the Wandering Albatross. It uses wind to extend its glide times and allow it use as little energy as possible during its migration. It seems that this wasn’t energy efficient enough for some individuals and they evolved into penguins over the millennia as swimming is much more efficient because there aren’t as many forces to contend with (Culik and Wilson, 1991).

The evolution of the penguin and its loss of flight is far from a complete story and I suspect we will find out more in the coming decades as more fossils are uncovered. Leave your thoughts in the comments!

Isn’t it nice to learn why not all birds fly? Some of us might assume that just because something has wings they won’t always stay grounded.

We hope you enjoy learning this about penguins and we love bringing you this information. Please consider supporting Penguins International by donating to us today.

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References

Culik, B., Wilson, R. and Bannasch, R., 1994. Underwater swimming at low energetic cost by pygoscelid penguins. Journal of Experimental Biology197(1), pp.65-78.

Alexander, R. (1999). One price to run, swim or fly?. Nature, 397(6721), pp.651-652.

Culik, B. and Wilson, R. (1991). Energetics of under-water swimming in Adelie penguins (Pygoscelis adeliae). Journal of Comparative Physiology B, 161(3), pp.285-291.

Elliott, K., Ricklefs, R., Gaston, A., Hatch, S., Speakman, J. and Davoren, G. (2013). High flight costs, but low dive costs, in auks support the biomechanical hypothesis for flightlessness in penguins. Proceedings of the National Academy of Sciences, 110(23), pp.9380-9384.

Tobalske, B. (2019). Biomechanics of bird flight. Journal of experimental biology, [online] 210(18), pp.3135-3146. Available at: https://jeb.biologists.org/content/210/18/3135.short [Accessed 8 Jul. 2019].

Why Are There No Penguins In The North Pole?

where do penguins live

Why Are There No Penguins In The North Pole?

by James Platt

If you asked a group of people where penguins live, you’d inevitably have a few say that pengiuns live in the North Pole. As we know this isn’t true, but it does beg the question: Why are there no penguins in the North Pole? And for that matter, the entire Northern Hemisphere?

What is the scientific research on why penguins live where they live?

There doesn’t seem to be much scientific research on the matter, so it must be explained using what is known about penguins around the world and then given the best answer possible. There are 18 species of penguins, of which 7 of them live in the Antarctic such as the Emperor Penguin (Aptenodytes forsteri) and King Penguins (Aptenodytes Pategonicus). The Yellow-eyed Penguin (Megadyptes antipodes) and Royal Penguin (Eudyptes schlegeli) are 2 of 6 species in Australia and New Zealand. There is one African Penguin (Spheniscus demursus) and 3 species that inhabit the Americas with the Galapagos Penguins (Sphendiscus mendiculus) living just slightly in the Northern Hemisphere, living so close to the equator.

Penguins live (almost) entirely in the Southern Hemisphere

With so much variety among penguin species it seems strange that they never moved farther north and filled more ecological niches as they did in the Southern Hemisphere. They found a home on the Australian and African continents where temperatures can be as hot as anywhere on earth, so temperature isn’t as much of an issue as most people may think. King or Emperor Penguins may not find the heat as easy to deal with as they are still adapted for the harsh environment of the Antarctic. However, the Galapagos Penguins, Little Penguins (Eudyptula minor) and African Penguins can withstand much hotter temperatures and could theoretically make the shift farther north.

Galapagos penguins
Figure 2: Volt Collection/Shutterstock

Looking at the Galapagos Islands, they are surrounded by hundreds of miles of open ocean. The larger varieties could swim that far if they were searching the Southern Ocean for food, but the smaller Galapagos Penguin doesn’t have a chance of swimming to Costa Rica or El Salvador which is why they have remained isolated to the islands (Heath and Randall, 1981). The same goes for the Snares Penguin (Eudyptes robustus) and Fiorland Penguin (Eudyptes pachyrhyncus) along with all the other species in Oceania if they were to move up through Papua New Guinea and Indonesia.

Some species may be adapted to the heat, but they are not adapted to move fast on land, so they will only stick to the coast and won’t often move north unless they are forced to. A behavioural study investigated how the African Penguin deals with heat and they spend most of their day in the ocean and only return to land in the late afternoon (Frost et al, 1976). At night, they are much less likely to move farther north in search of territory as it is more dangerous at that time. In South Africa and Namibia, the African Penguin also has a lot more predators to be wary of, making any move farther north a risky one. In the Antarctic, when the penguins are on the ice they have no real threats from predators, so they have not evolved much protection against land predators. But on these other continents they can be real threats, especially to the chicks.

In Antarctica, penguins and their nest sites are left relatively untouched by humans and they are left to breed and live in peace. African Penguins have been pushed to the brink by humans taking their guano for fertiliser and trampling their burrows (Trathan et al, 2014). Many of the southern island species were hunted for oil until the last century. So, life outside of the Southern Ocean isn’t great for many of the species. It might be that penguins couldn’t survive any more outside pressure from humans and any populations that have successfully moved farther north were pushed to extinction before they could gain a proper foothold in the area.

All these reasons combine to make a compelling case for why there are no penguins in the Northern Hemisphere. It’s likely since penguins won’t move over large distances on land, they struggle to find new territory farther north. Any that do make it are likely either scared off by curious humans or killed by predators as they will make an easy meal for many land predators. The Galapagos Penguins probably won’t make it any farther due to their geographic location being so far from anything else. If they were on the other side of South America then they very well could have used their adaptation to hot climates and island hopped all the way to North America through the Caribbean and Cuba.  The closest thing to a penguin that did live in the North Pole was the Great Auk (Pinguinus impennis) and was subsequently hunted to extinction in the 1800s. Just as the Dodo (Raphus cucullatus) had no fear of humans because they hadn’t ever faced predators, the Great Auk suffered the same fate. So maybe its better if penguins stay South and remote for now.

Royal Penguins
Figure 3: Sonja Ross

What do you think? Is there another reason they haven’t moved farther north? Leave us a comment. Also, please help us continue to learn more about penguins by donating to Penguins International.

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References:

Frost, P., Siegfried, W. and Burger, A. (2009). Behavioural adaptations of the Jackass penguin, Spheniscus demersus to a hot, arid environment. Journal of Zoology, 179(2), pp.165-187.

HEATH, R. and RANDALL, R. (1989). Foraging ranges and movements of jackass penguins (Spheniscus demersus) established through radio telemetry. Journal of Zoology, 217(3), pp.367-379.

Trathan, P., García-Borboroglu, P., Boersma, D., Bost, C., Crawford, R., Crossin, G., Cuthbert, R., Dann, P., Davis, L., De La Puente, S., Ellenberg, U., Lynch, H., Mattern, T., Pütz, K., Seddon, P., Trivelpiece, W. and Wienecke, B. (2014). Pollution, habitat loss, fishing, and climate change as critical threats to penguins. Conservation Biology, 29(1), pp.31-41.

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