Even if you’re new to keeping reptiles, you’ve likely learned that they’re cold-blooded. In other words, they don’t produce their own body heat like mammals do (with some very unique exceptions). Because of this, reptiles need to actively regulate their body temperature throughout the day. Understanding how they do this is essential for creating enclosures that meet their needs and keep them healthy.
What Is Ectothermy?
An ectotherm is a cold-blooded animal, which is one that cannot control its own body temperature internally. (This is the opposite of an endotherm, like us, that creates its own body heat.) Ecto- means “outside,” while endo- means “inside”; ectotherms get their heat from outside their own bodies, while endotherms make it inside.
Since reptiles can’t make their own heat, they need to acquire it from other locations. That’s why you see animals basking, burrowing, or sticking themselves into nooks and crannies where residual heat might still be lingering.
How Reptiles Gain and Lose Heat
Reptiles can gain heat in many ways, not just sitting in the sun. However, ectotherms aren’t solely motivated by the instinct to “get hotter.” Rather, ectothermic animals have a particular internal temperature that is ideal for them based on the time of year, how recently they’ve eaten, whether it’s breeding season, and more. Like a thermometer, their bodies track heat, and when things are hot enough, they’ll seek to cool down. This process is called thermoregulation.
Some of the ways that animals in the wild regulate their own body temperature include:
- Radiation: Even if an animal isn’t in direct sunlight, it can get warmer simply by standing next to something warm. This is why some lizards burrow under rocks during the day. The rock will warm up, allowing the lizard to get warmer without exposure to predators.
- Conduction: Heat from the sun soaks into other objects. Even after the sun moves, those objects can remain warm for some time. Energy traveling from this warmer source and into the reptile heats the animal via conduction. This is the most common type you'll see in captive care; your lizard or snake probably sits on their basking spot to warm their stomach.
- Convection: Water is one of the most potent ways to transfer heat. It wicks away heat faster than air does, so reptiles that need to cool down often do so by getting into the water. This is even truer if the reptile gets out again, where the water has already gotten rid of some heat, and then the air helps the rest to evaporate, taking heat with it (just as your sweat does on a hot day).
- Coloration: Dark colors absorb heat better than light colors. Thus, some reptile species (like many monitors) that require very high heat tend to have darker or even black scales.
What Does This Mean for Your Care Routine?
In order for your reptile to stay healthy and safe, it’s up to you to meet their heating needs. First and foremost, that means giving them not just access to the heat they need, but also to the opportunity to cool down. Create a gradient in your enclosure by placing your heating elements at one end, rather than in the center or spread across the top. This allows for a warm side and a cool side.
Once you’ve got your heat gradient set up, be sure to measure it correctly. Thermometers attached to the back of the enclosure won’t tell you the whole story; they only measure the temperature in the air (called the "ambient" temperature). They say nothing about how hot a surface is. An infrared thermometer, on the other hand, uses a laser to read surface temperature so you know whether your reptile is truly getting the heat they need.
With your temperatures set up, consider how the enclosure is decorated. Is your basking spot large enough for the animal to spread out? Does the cool side have a place for them to rest or sleep, or is it too cluttered?
Reptiles use heat to digest their food and absorb calcium and D3. Thus, you should plan to feed your reptile at a time of day when they’ll still have plenty of opportunity to bask. Avoid feeding right before you turn the lights off overnight (if you use heating elements that turn off for a period every day). While many reptiles are adapted to digest even tough food items like bones, even soft and highly digestible foods like Reptilinks still need time to break down in the heat.
What Happens If My Reptile Can’t Thermoregulate?
You might think that being a little too warm or too cool isn’t a problem, but it can have dire consequences for your pet. Chronically being too cold can leave your reptile with digestion difficulties that can lead to regurgitation, impaction, and even lessened immune function. Too much heat, on the other hand, might dehydrate them, cause burns, damage nerves, or even lead to death.
As you consider how to take care of your pet, invest extra time in making sure your heat setup is just right. Ectotherms count on heat adjustments throughout the day, and by meeting those needs, you can keep your pet happy, healthy, and energetic!