14 Thermal Images of Animals

Take a look at the thermographic infrared world of lions, cats, and bears.

hand holds a thermal imaging camera to look at body heat in animals

Westend61 / Getty Images

Thermal imaging, also known as thermography, captures infrared radiation and turns it into an image similar to standard photography, which does the same thing with light in the visible spectrum. Thermal imaging is an important tool for science because warmer objects emit more radiation, which translates on thermal images as brighter colors (the brightest possible value for a thermal image is pure white).

Thermal cameras are used in a wide variety of industrial and commercial settings, from parts manufacturing (to make sure things stay the proper temperature throughout the production run) to utility line repairs (faulty lines and switches show up hotter than they should). In the world of sustainability, they are used by designers and builders to detect leaks in inefficient and/or old building envelopes.

One of my favorite applications of the technology is thermal images of animals. I'm an armchair biologist and am fascinated by the mind-blowing morphological diversity created by evolution and natural selection. I am also a huge fan of biomimicry and know that there is an enormous amount that we can learn from the natural world to better inform how we design our own human-made environment. Seeing how animals from different parts of the world manage their internal heat could offer some fascinating insights. At the very least, they're really cool to look at. Here are 14 really cool thermal images of animals.

1. Ostrich

Thermal image of ostrich
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Ostriches are the largest birds in the world. They can weigh hundreds of pounds, stand more than nine feet tall, and can run 40 miles per hour for more than 30 minutes. Ostriches are native to Africa and can be found throughout much of the continent. They need to be able to both vent heat during hot days, while being able to preserve it during cool nights. As the thermal images show, the giant bird throws a lot of heat off its legs and long neck. At night, when ostriches settle down for sleep, their legs are tucked up underneath them, helping to preserve warmth. During hot days, their feathers reflect heat away and running around helps to circulate cooler air over their skin.

2. Lion

Thermal image of lion
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Lions are enormous predators found in Africa and Asia that sit firmly atop their local food web (if you factor out humans). They are considered a vulnerable species and have seen their numbers plummet over the years because of hunting and habitat loss. The estimated number of lions in Africa has fallen as much as 90% since the 1950s and has showed no signs of slowing over the last few decades. Conservation efforts have helped to carve out protected habitat for the King of the Beasts, but there's more work to do.

In its natural range, the lion has to deal with the hot days and cold nights of the savanna, and its thermal image shows how the thick mane of a male helps it retain warmth during the night while he pants off heat during the day.

3. Vulture

Thermal image of vulture
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Vultures describe any number of actual species of large scavenger birds and are found throughout the world. They don't have a particularly sterling reputation, but are in fact a hugely important player in natural systems. India has suffered from a precipitous drop in the vulture population caused by the widespread use by farmers of a painkiller that soothes their cows but kills the scavenging birds. Without vultures to eat and break down dead animals, the bodies are left to rot away slowly where they fall or are piled up in huge mountains of stink that attract and support roving bands of vicious dogs.

4. Dog

Thermal image of dog
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Wow! As you can see in the image, the heat is emitted from the dog's mouth primarily—which makes sense, as they cannot sweat through their skin and must rely on panting and heat release via ears and paw pads (not pictured) to regulate body temperature.

5. Snake

Thermal image of snake
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Snakes are cold-blooded for a reason—they barely show up in thermal imaging! (That's a human arm that's you're seeing in yellow.) While there are thousands of different kinds of snakes, they all share the trait of using external heat sources to regulate internal temperature. Most exist in a spectrum between being cool and slow-moving or warm and active, and have evolved to efficiently retain any heat they pick up from their environment.

6. Mouse

Thermal image of snake eating a mouse
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

This image shows the striking contrast between the warmth thrown off by a small mouse and that of a heat-stingy snake — which, as explained above, relies on external sources for that heat.

7. Lizards

Thermal images of lizards
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

These toasty lizards look like they're having a great time lounging on some very warm rocks. Lizards thrive in hot, dry, sunny climates, which is why they're usually found in the desert. Ideal body temperatures vary between species, but they tend to like it warm. Desert iguanas, for example, have a body temperature range between 100 to 108 degrees Fahrenheit. When they start to exceed that, they'll move to a cooler, shadier spot.

8. Deer

Thermal image of deer
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Deer are found throughout the world and are made up of a huge number of individual species. I suspect that the kind of deer seen in this thermal image lives in a temperate environment where it's valuable to be able to retain internal body warmth. Though it's positively glowing around its mouth and eyes, the dark colors found on its body reveal how well its fur retains much-needed heat.

9. Tarantula

Thermal image of tarantula
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Tarantulas have a unique circulatory system that uses a blood-like liquid called hemolymph to transport oxygen throughout its body. This tarantula's morphology vents its heat almost entirely on the top of its abdomen.

10. Cat

Thermal image of cat
Lcamtuf / Wikimedia Commons / CC BY-SA 3.0

Meow. Cats maintain a constant core body temperature, which means they'll shiver and sweat, depending on what needs to be done to stay at the right temperature. They can only sweat through their paw pads, however — and licking those pads can stimulate sweating, which is why cats need to drink lots of water when the weather is hot.

11. Polar Bear

Thermal image of polar bear
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Polar bears are masters of retaining body heat, as you can see in this thermal image. Millions of years of evolving in an Arctic environment have perfectly honed their ability to hold on to as much of their internally generated heat as possible. An interesting note about the polar bear is that their skin is actually black; their clear hollow hairs channel the sun's rays onto their dark skin and reflect light away to give them their snowy white coloring.

12. Bats

Thermal image of bat
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

The wings of these bats look like they're doing a darn good job keeping warm. They need it, since they're warm-blooded and maintain their body temperature internally. If they get cold, their metabolism slows, though this can also be an energy-conserving tactic for bats.

13. Eagle

Thermal image of eagle
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

"What, are you talking to me?" Eagles (and other raptors) use something called a counter-current exchange to control their body temperature. Raptor Resource explains, "Warm arterial blood flowing from an eagle's core into its feet passes cool venous blood flowing the other way. Heat is exchanged, warming the blood flowing into its core and cooling the blood flowing into its feet."

14. Ringtailed Lemur

Thermal image of lemur
Arno / Coen / Wikimedia Commons / CC BY-SA 3.0

Ringtailed lemurs are endemic to Madagascar and their range has been pushed to forests on the southern end of the island. It can get warm in Madagascar and, as this thermal image shows, lemurs have evolved the ability to throw a lot of unwanted heat off their large tails.