Penguins are overheating! Yep, you read that right!

By Beth Storey-Jones

What do you imagine when you think of penguins? 

• Highly adapted?
• Caring parents? 
• Amazing swimmers? 
• Looking fly in their tuxedos? (no pun intended)

Well you would be 100% correct on all accounts. You might also worry about how they may struggle to keep warm? In fact, this isn’t their primary issue. They’re actually more at risk of overheating! Yes, I did say overheating. This is a real problem and is becoming detrimental to penguin populations. Let me explain!

Brief penguin anatomy and physiology lesson

First, let’s take a brief look at a penguin’s anatomy and physiology. They are aquatic, built for life at sea. To allow them to thrive in the water, warm-blooded animals need to be well insulated. Whales have blubber, seals have thick fur pelts, but birds have neither. Evolutionarily speaking, birds avoided adaptations that would hinder flight. So, penguins have had to use pre-existing characteristics and tweak them to survive in their niche, this being their feathers.  As a result, these feathers are short, ridged and interlock [1] to form an air trap (figure 1). Which is equivalent to a dry suit. Any heat obtained by the bird is kept in between the base layer of the feathers and the top layer of the skin, and works well as an insulator when in the water. The trouble comes when this same heat is not released, as when they return to land.

Fig. 1 Penguin skin showing feather density [1]

Penguin Distribution – Where do they live?

Fig. 2 Penguin Range Map [2]

Contrary to popular belief, most penguin species live in temperate and even tropical zones, not Antarctica (Fig. 2). Consider the Little Blue Penguin, who breeds up and down the coasts of Australia and New Zealand [2]. They often only come ashore once the sun begins to set. A more popular species, the Galapagos Penguin, avoids direct sunlight by creating nesting areas in shaded lava rock cracks. Water temperature can also be as high as 30oC (86.0°F) around the equator [3] and for a bird that has to maintain an internal body temperate of 39oC (102.2°F) this can be challenging. With their feathery armour only just able to regulate this temperature, prevention methods aren’t always the best medicine.

So, how do penguins combat hyperthermia? To answer this question in short, thermoregulation adaptations. It’s really interesting, so I’ll elaborate! You may have noticed that quite a few bird species have naked legs or webbed feet, or both. These areas of the body house complex blood vessels which can constrict to control the amount of heat loss when cold or expand to lose heat when the animal is too hot, comparable to a radiator [3]. Penguins such as the Humboldt Penguin also have featherless faces. Behaviourally, penguins pant. Which evaporates the body’s moisture while using up body heat to do so. Much like your dog, when he’s retrieved his favourite tennis ball for the 100th time. Penguins will also hold their flippers out to the side to allow breezes to cool them down even further.

Chicks at risk

Penguin chicks are also at risk of overheating. Their soft down is even more efficient at heat retention. While unable to thermoregulate, chicks are sheltered from the sun by their parents. Unlike the adults, their flippers are also covered in insulating down. So, the babies have to rely on their disproportionately large (and cute) feet (Fig. 3) to act as a personal radiator [3]. On exceptionally hot days, juveniles have been observed essentially laying like a starfish on the ground to expose their feet. Some species will even stand in water. 

Fig. 3 The extra-large feet of a penguin chick [3]

Challenges ahead…

So far, it has been explained that heat regulation is a bit of a challenge for the penguin. That is without even taking into consideration our global warming crisis. I know, I know, everyone is talking about it. But it is a vital element to consider in the lives of our beloved penguin friends. The finely tuned adaptations we have talked about did not happen overnight. It was through the millenia-long trial and error process of evolution and will still be ongoing today. These adaptation changes aren’t necessarily a problem, but it’s the small window of opportunity that these animals (as well as other species) have to do it in when temperatures rise quicker than evolution. Sadly, this is where the detrimental part comes in. Sea temperatures are increasing. Penguin chicks are struggling to survive due to poor food quality and quantity from these temperature increases[4]. The warmer climes seen in Antarctica recently are causing unprecedented rainfall and the melting of potential snowfall. This can be damaging to eggs that must be kept dry and warm. And the chicks may also become muddy and wet and can succumb to hypothermia because their down feathers are not waterproof[4].

Let’s bring it all together. Penguins live in water. They inhabit not only the harsh, dry and cold parts of the world, but surprisingly also some of the hottest. They have finely-tuned mechanisms to allow them to do so. Such as radiators for feet and dense plumage for when they need to stay warm. But these adaptations are so specialised to their surroundings, that any changes can be fatal. With sea temperatures rising, food availability and competition is high, as well as the risks of chicks being exposed to hyper or hypothermia. This brings a bit of a chilly end to an extremely cool topic!

Thinking of penguins in general, do you think they would overheat? Did you like what you learned by reading this blog? Leave a comment below. And please help us to continue to provide you with penguin news articles by donating to Penguins International.

Read more about penguins in some of other blogs:

• Cold Feet: Why Don’t Penguin’s Feet Freeze?

• What’s up with “Down”?

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Reference List

1. DeNapoli, D. 2010. The Great Penguin Rescue. New York. Free Press. 
2. Muller-Schwarze, D. 1984. The Behaviour of Penguins – Adapted to Ice and Tropics. New York. State University of New York Press
3. Kaiser, G. 2007. The Inner Bird: Anatomy and Evolution. Vancouver. University of British Columbia. 
4. Sidder, A. 2016. Antarctica Could Lose Most of Its Penguins to Climate Change. [online]. National Geographic. Available from: https://www.nationalgeographic.com/news/2016/06/adelie-penguins-antarctica-climate-change-population-decline-refugia/ [Accessed 24 October 2019].

Figures

1. National History Museum. 2018. Ever wondered how Emperor Penguins survive temperatures of -60 degrees centigrade? Their feathers are densely packed as these photos show but as researcher Cassondra L. Williams and colleagues discovered there is more to the story than meets the eye. [online]. Twitter. Available from: https://twitter.com/nhm_oology/status/1022076201828012032 [Accessed 24 October 2019].
2. Kikkawa, E., Tsuda, T., Sumiyama, D., Naruse, T., Fukuda, M., Kurita, M., Wilson, R., LeMaho, Y., Miller, G., Tsuda, M., Murata, K., Kulski, J., & Inoko, H. 2009. Trans-species polymorphism of the Mhc class II DRB-like gene in banded penguins (genus Spheniscus). Immunogenetics. 61, 341-352.
3. Tennessee Aquarium. 2017. Call It “Sasquawk”: Big Feet a Distinct Feature of the Aquarium’s Newest Penguin Chick. [online]. Tennessee Aquarium. Available from: https://www.tnaqua.org/newsroom/entry/call-it-sasquawk-big-feet-a-distinct-feature-of-the-aquariums-newest-pengui [Accessed 24 October 2019].