They’re standing on ice, all day, in bare feet. How do those things not freeze?
Penguins are incredible examples of how animals can adapt to some of the harshest conditions on Earth. Living in the frigid waters of Antarctica, they manage to thrive in a place where most humans would die within hours.
You might have learned about their feathers, which help lock in heat. They also have a thick layer of fat, providing additional insulation.
But there’s one area of a penguin’s body that isn’t covered by feathers, that is in constant contact with the freezing exterior. And the penguins are literally putting their weight on it to survive.
Their feet.
If you or I stood outside, barefoot, in the Antarctic snow, we’d quickly start suffering some pain and nasty side effects, probably leading up to eventual frostbite. But penguins do this for all their lives without any issue!
- What, exactly, is frostbite?
- How do penguins avoid it?
- Are there any other myths about penguins that should be dispelled?
Let’s get the chilly details — and no fishy business here!
Frostbite is bad because frozen things expand
First off, let’s talk about what penguins don’t get: frostbite. What is it, anyway?
Put simply, frostbite is the term for when our tissues freeze. Mild frostbite is when just the skin freezes, but as the freezing sinks in deeper, the damage becomes more and more severe. Mild cases can be reversed simply by thawing, but more severe cases can sometimes lead to amputation — and with severe cases, thawing actually causes even more damage.
But why does freezing cause damage?
The answer comes down to the liquid inside our cells. Normally, this liquid is kept hot by our blood, which constantly circulates and distributes heat from our core out to our extremities. But when we’re cold, our body constricts our blood vessels, saving the heat for our core, and causing our limbs to get colder.
Why is a cold limb a bad thing? Think about what happens if you put a super-full water bottle in the freezer. When it freezes, the water expands, which might even split the bottle open.
The same thing happens to our cells when they freeze. Tiny ice crystals form inside our cells when they aren’t being kept warm. Those crystals are larger than the liquid, and they can either cut at our cells and cause damage, or even pop them open.
Additionally, less blood flow to our limbs means less oxygen is reaching the tissues there. And without oxygen, the muscles of our skin, muscle, blood vessels, and other tissues in our limb begin to die.
Frostbite can occur whenever tissue is exposed to temperatures below freezing (0 degrees Celsius, 32 degrees Fahrenheit).
And in the Antarctic, temperatures can drop as low as -60 degrees Celsius during blizzards. That could kill a human in minutes.
So how do penguins stand it (no pun intended)?
Penguin feet stay safe through multiple methods
It turns out that penguins use a combination of both biological and behavioral mechanisms to keep their feet from freezing solid and snapping off their rotund little bodies.
First, let’s talk biology! Penguin feet are much different from our own feet. Our feet have lots of soft skin, neurons, and muscles, so that we can control them and experience lots of sensations through them. That soft brush of a feather drifting along the bottom of your foot? That’s because of our neurons and tissues.
Penguin feet, on the other hand, are mostly just made of bone and cartilage. There isn’t a lot of tissue there to even take damage.
Next, blood vessels. Penguins do have blood vessels that flow down to their feet, but they can constrict the diameter of those blood vessels to reduce how much blood goes that way. (We instinctively do the same thing when we get cold.) This way, they can drop the temperature of their feet intentionally, reducing overall heat loss.
So, not a lot to take damage, and the ability to carefully regulate how much heat flows to the feet.
Meanwhile, penguins also show a couple of behaviors to help keep their feet from freezing. They hunch down over their feet, using the warmth of the rest of their body to keep the feet from dropping below freezing temperature. They’ll also alternate which foot makes contact with the ground, first lifting one foot, and then the other.
Put their biology and behavior together, and we see how penguins keep their feet from freezing.
Any other penguin myths we should tackle, while we’re here?
Penguin feathers: quality, not quantity
While we’re on the topic of penguins, let’s take a moment to talk about their feathers.
It’s commonly cited on the internet that penguins have way more feathers than other birds, more than 15 per square centimeter, and this explains their ability to retain heat. Other papers have claimed anywhere from 11 feathers to 46 feathers per square centimeter, but there doesn’t seem to be any consensus.
However, more recent evidence suggests that penguins actually don’t have tons of feathers; firsthand counts suggest that the number is only about 9 feathers per square centimeter.
The heat isn’t being trapped in their fur by sheer number of feathers. Rather, there are multiple specialized types of feathers. Their main, large feathers have little bits of down called afterfeathers that help trap in warmth, but they also have high numbers of plumules, smaller down feathers attached directly to the skin, like putting on a warm sweater as a base layer beneath the winter coat.
It just goes to show, it’s probably better to develop a specialized solution than to just try and solve a problem with sheer numbers!
In summary: lack of tissues and blood flow control prevent frozen penguin feet
Penguins have feet, just like we do, but that’s about where the similarities end. Unlike our soft, fleshy, nerve-filled feet, penguin feet are sparse affairs made mostly of bone and cartilage, without a lot of tissues to risk damaging in the frigid Antarctic cold.
Penguins also lift their feet off the ground, one at a time, to help minimize the heat loss through contact with the earth. They’ll crouch down over their feet, trapping heat beneath their body, and they’ll control how much blood flows down to the feet — just enough, not too much, to keep them just above freezing.
Between their feet and their specialized types of feathers, penguins are well equipped to handle the temperatures of Antarctica, often below -30 degrees Celsius.
The bigger risk to them? Climate change. Our current projections suggest that, even assuming we continue to implement clean energy strategies, we’ll still see a 2 degree Celsius increase in global temperature, which will drastically reduce penguin populations.
Let’s help preserve penguins and their uniquely evolved feet.
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