Sonia Peck is a penguin keeper at the Two Oceans Aquarium.

A not so well-kept secret is that the African and northern rockhopper penguins in our Penguin Exhibit, brought to you by Old Mutual Finance, is among the most popular creatures at the Two Oceans Aquarium. 

Here are some things you might not know about penguins ...

Why are some penguins big and others small?

Big penguins find it easier to keep warm because they produce more heat in their muscles and can hold heat more efficiently. So, the bigger penguins live in colder climates, and the smaller ones in warmer climates. Big penguins can also dive deeper and stay down longer than small penguins.

The smallest penguins feed almost entirely in surface waters, whereas big penguins catch food far below the surface, which may be a more important reason as to why they come in different sizes.

The emperor penguin is the largest penguin at 1,3m.

Emporer penguins in Antarctica. Photo courtesy Flickr/US Geological Survey (Public domain)

The little blue penguin is the smallest at 33cm.

Little Blue Penguins in New Zealand. Photo courtesy Flickr/Andrea Schaffer (CC BY 2.0)

How can you tell the difference between male and female penguins?

In almost every species of penguins the sexes are visually very similar. However, males in each species are usually slightly larger then females, with slightly heavier bills. Another way of telling is by noting their behaviour: males are usually the first to arrive at colonies and take up nest sites.

Adélie penguins in Antarctica. Photo courtesy Flickr/Christopher Michel (CC BY 2.0)  

In courtship they are also more active and aggressive, more likely to fend off rivals, more likely to call to attract partners, and more likely to be involved in fights.

How fast can a penguin swim?

Penguins are very lively in the water and dart around quickly. Most can swim at around 7 to 8km/h. They can sprint faster in short bursts with king and emperor penguins doubling this speed over short distances. However, when travelling far (for example from one feeding site to another), penguins travel more slowly, averaging around 3,5 to 7km/h.

Northern rockhopper penguins swimming through the Ocean Basket Kelp Forest Exhibit at the Two Oceans Aquarium. Photo by Renée Leeuwner

On long journeys, penguins usually swim together in groups, leaping out of the water every few seconds and diving back in again. This is called porpoising. Each leap allows them to snatch a breath, taking in the oxygen to keep them moving and getting rid of the carbon dioxide that would otherwise poison them. In porpoising, penguins swim constantly, which is far more efficient than stopping every few seconds to breathe. On long journeys however, they take rest stops too.

Why don’t penguins’ feet freeze?

Penguins have a thick layer of blubber, covered in a layer of plumage, ensuring their body heat is retained. However, heat escapes from two main areas: the beak and the feet. But this can actually be a good thing. By having areas that heat can readily escape from, penguins are able to regulate their body temperature, keeping them from overheating at times. In addition to acting as temperature control, penguin feet are bare for other reasons as well. Penguins need them to grip the ice and help to steer when they are swimming in icy water.

The feet of a king penguin on Salisbury Plain in Antarctica. Photo by Werner Sinclair

Penguins have a highly developed circulatory system that is able to control how warm their feet actually get. There are arteries in the penguins’ legs that are able to adjust blood flow to the feet, based on temperature. The arteries restrict blood flow when it’s colder, meaning less blood has to travel through the cold feet, helping to keep the penguin warm. (Humans actually can do this to some extent as well.) When the penguin is too warm, the opposite happens and the arteries allow more blood flow to the feet, cooling them off.

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