Why Penguins’ Feet Don’t Freeze

Kara asks: A penguin’s feet are always on ice, so why don’t they freeze or have some sort of evolutionary built in insulation?

penguinsThere are many different species of penguin, and while our minds might take us to those living in the Antarctic tundras, freezing feet isn’t something every penguin has to contend with. In fact, there are some species of penguin living on the equator that need their feet to be cool to help them battle the heat.

For the poor penguins who do live in lands of snow and ice, freezing isn’t usually an issue. Most of their body is covered in plumage that is waterproof, which keeps them warm even in the chill of an arctic breeze. Emperor penguins, probably the most recognizable species, have one of the highest feather densities of all birds, with about 100 feathers per square inch. Underneath that cozy plumage is a layer of blubber that acts as an additional blanket. With these two layers, penguins typically can stay toasty warm.

However, heat does escape 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 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.

To answer your question less generically, 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 blow to the feet, cooling them off.

Besides this built in mechanism, a more mundane way the penguin can control their feet’s temperature is simply to huddle down around their feet so that their body is keeping them more protected and warm. They also sometimes rock back and sit on their tails for a while to get their feet off the ice.

Typically with this heat regulation, the penguins’ feet are kept a few degrees above freezing, and not usually much warmer than that so that the penguins don’t expend too much energy in heating their feet, unless they are already too hot, in which case the loss of heat is a good thing.

Energy is of particular concern to Emperor penguin dads who incubate their eggs for 64 days away from the coast and don’t eat anything during this time—so, preserving calories by not losing much heat is a must! The good news is, with their circulatory system, their feet won’t be turning into ice blocks unless their stored food situation gets critical.

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Bonus Penguin Facts:

  • There are between 17-20 different species of penguin. Penguins are one of about 40 types of birds who can’t fly, a list which also includes emus, kiwis, ostriches, and cassowaries.
  • Penguins make up for their inability to fly with their impressive swimming abilities. Most penguins can swim underwater between 4-7 miles per hour. Just before diving into the water, they release air bubbles from their feathers, which allows them to achieve their impressive speed. The Gentoo penguin can reach speeds of up to 22 miles per hour, making it one of the fastest penguin swimmers.
  • Penguins almost always live in the southern half of the globe, though the Galapagos penguins—who live nearest to the equator—will sometimes be spotted just north of the equator.
  • Penguins are carnivores with a diet that consists almost exclusively of seafood. During the summer, adult penguins feast on an average of two pounds of fish, squid, and krill per day (in the winter, it’s usually less than a pound). Their diet means that they also ingest a lot of seawater while hunting and eating. Penguins have a special way to remove the excess salt. Their supraorbital glands filter salt from the bloodstream and then excretes it through the bill. (However, they don’t drink seawater to stay hydrated; they turn to freshwater melt pools for that.)
  • Penguins’ cute tuxedo-like pattern helps them stay camouflaged in the water. Aerial predators looking for their next meal will have difficulty seeing their black backs as they blend into the dark water; predators from below would see their white bellies, which would blend in with the light above.
  • Most species of penguins live in giant colonies that range in size from 200 to hundreds of thousands of birds. The colonies are often so large that they can be spotted from space, largely thanks to all of the penguin waste that goes along with living with so many other birds. It discolours the ice, making the area where the penguins live easy to spot.
  • Thirteen species of penguins are considered threatened or endangered. Two species with rapidly declining population are the Galapagos penguin and the erect-crested penguin, a native of New Zealand. One of the biggest issues penguins are facing is pollution and climate change, which is making their habitats disappear and their food more scarce.
  • The largest penguin is the Emperor penguin, which is usually around 45 inches tall and weighs around 90 pounds when full grown. The smallest is the fairy penguin, which is only 10 inches tall and 2.5 pounds.
  • Emperor penguin males not only incubate eggs, they also feed the hatched young with milk produced in their esophagus.
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