In fact, penguins have cold feet too!!!

Audit expert: Ran Hao

Well-known science writer

When you take off your shoes and socks and stand barefoot on the ice, how many minutes can you last? You and I are all mortals, and we are probably bragging for 10 minutes and then failing after one minute on the ice - and this may be the result obtained in a warm room - but if you are a penguin from Antarctica, let alone indoors, even in the extremely cold Antarctic, it is not a problem to stand on the ice at -59.4 degrees Celsius for 2 months.

So the question is, why are penguins not afraid of the cold or frozen feet?

Source | Pexels

Why aren't penguins afraid of the cold?

Let’s first talk about why penguins are not afraid of freezing. In fact, like humans, penguins are warm-blooded animals and need to consume their own energy to produce heat. The reason why they are not afraid of freezing is, of course, because they wear thick “Penguin brand down jackets”!

Penguin feathers source | Unsplash

The penguin's thermal insulation equipment is much better than the down jackets sold on the market. Although it looks like it has only a thin layer of feathers, it actually has 4 layers of "thermal insulation material"!

We will introduce them from the outside to the inside. First, the outermost layer is a black and white "feather jacket". The oily feathers of penguins are arranged very closely, in overlapping, dense scales, with more than 70 feathers covering every square inch. Because this feather is oily, it is naturally waterproof. Therefore, when penguins "winter swim" in sub-zero ice water, seawater is difficult to penetrate and thus will not break through its insulation line. The black and white color matching of penguins is also very particular. We know that when light shines on an object, part of it will be absorbed and the other part will be reflected. The darker the color, the more visible light is absorbed, so the black part helps to absorb light when the sun is out, thereby converting light into heat.

The second layer of warmth-keeping material is probably something most people would never think of: air! Between the feathers and the skin, there is a layer of "air clothing". This is not the emperor's new clothes. The air actually plays the role of insulation and heat insulation, making it difficult for the heat generated in the body to dissipate.

The third layer is the "leather warm clothes", that is, the skin. The last layer is the penguin's subcutaneous fat layer , which is 2-3 cm thick. This is their warmest "cotton coat"!

Source | Sohu.com

Why aren't penguins' feet afraid of cold?

Next, let's talk about why penguins are not afraid of freezing their feet. Friends who have seen penguins know that although they wear thick "down jackets", their feet are exposed and have no hair, just like us humans. So in fact, their feet are also very cold, only 1-3℃, but this temperature will not affect the actions of penguins.

The reason why people cannot stand on the ice for a long time is related to the poor cold resistance of our skin. When people's feet are in a low temperature or humid environment for a long time, the blood vessels on the surface of the body will spasm, reducing blood flow. Therefore, even if you stand on the ice for a few hours, your feet will be damaged due to tissue ischemia and hypoxia, and even venous congestion, and finally swelling, itching, erythema, ulceration and other symptoms of frostbite will appear.

Source | pixabay

But it is different for penguins. Their feet are mainly composed of tendons, toe bones and a thick layer of skin. The muscles that control movement are mainly located in the legs, hidden in thick fat and feathers. There is also a thick fat protective layer under the skin of the soles of the feet... But these are not the real secrets of penguin feet's anti-freeze. The reason why penguins are not afraid of frozen feet is that they have a special blood circulation system - a countercurrent heat exchange system .

Source | Wikipedia

Like humans and penguins, blood vessels are divided into arteries (represented by red) and veins (represented by blue). In a cold environment, arterial blood flows from the core of the body to the limbs and has a higher temperature; venous blood returns blood from the colder limbs to the core of the body and is usually at a lower temperature.

For humans, because the limbs themselves also generate heat, the temperature of the human blood does not drop quickly as it moves away from the heart, which slows down the drop in blood temperature to a certain extent. However, in the freezing Antarctic, if the temperature difference between the feet and the ground is too large, it is easy to produce rapid heat exchange with the cold ground, causing the body to lose heat quickly. Therefore , in order to cool the arterial blood before flowing to the feet, penguins have evolved a reverse heat flow exchange blood vessel arrangement.

Source | Zhihu

The special thing about this system is that the arteries that supply blood to the feet and the veins that return to the heart are entangled together, so that the warm arteries can transfer heat to the colder veins in time, and the temperature of the venous blood rises rapidly; similarly, the veins are also equivalent to a "refrigerant", which can quickly and promptly reduce the temperature of the arterial blood. In this way, the temperature difference between the arteries transmitted to the penguin's feet and the ground is reduced, thereby reducing the heat loss caused by heat exchange with the cold ice surface, allowing them to maintain a sufficient temperature so that their feet will not be frozen.

When the weather is extremely cold, penguins will tiptoe and stand on their heels to reduce their contact area with the ground, thereby reducing heat loss.

Penguin walking on heels Source | Internet

Therefore, if you are not gifted like penguins and have not mastered the trick of "freezing people with beauty", you still have to pay attention to keeping warm in cold areas!