Temperature Consistency is the single most important facet of successful snake keeping!

Snakes are ectothermic – essentially meaning that in lacking the ability to create their own body heat, they depend on temperatures immediately around them to facilitate proper metabolism.

Quick Answer

UT (Under Tank) and OT (Over Tank) are the most common heating methods used for corn snake terrarium.
We recommend UT heating since it more accurately simulates how corn snake achieves proper body heat in the wild and is the safest way to heat your snake.

By adjusting the depth of the cage substrate, it is easy to achieve proper appetite and digesting temperatures for your corn snake without the aid of electronic controllers.

If the warm-side hide is over 85°F (29.4°c) inside, increase the substrate depth so the snake is farther from the heat source. Conversely, if the inside of the warm-side hide is in the low 80sF (26.7°c – 29°c) or below, decrease the substrate depth to move your snake’s primary hide closer to the heat source that is under the cage.

In rare instances, UT and OT heaters are jointly advised in very large enclosures, but in positioning and adjusting devices and hides, it is essential to remember that the appetite and digestion TEMPERATURE GOAL of 80°F – 85°F (26.7°c – 29.4°c) is only achieved if your snake wants to access that ideal temperature zone.

I recommend that the size of the UT heater never exceeds 1/4 of the length of the cage. If too large, it’s possible to place the warm hide where it will overheat. If you already have a UT heater that’s too large, place the hide only partially above it. If the hide is too warm, the snake will opt to repose in cooler zones of the cage, thereby not achieving body temps necessary for appetite and digestion.

Detailed Answer

Snakes are ectothermic – essentially meaning that in lacking the ability to create their own body heat, they depend on temperatures immediately around them to facilitate proper metabolism. When you hear the term cold blooded – which originally referred to the fact that unlike most mammals, snakes are often cold to the touch – the primary implication is that their bodies are incapable of creating heat. Of course, the result of both explanations is the same. Even at proper cage temperatures, your snake will feel cold to your touch because your outer skin is roughly between 90ºF and 95ºF (32ºc and 35ºc) indoors. Therefore, you may falsely preceive that your snake’s body is unacceptly cold, when in fact, the temperature may be ideal for appetite and food digestion. Only thermometers that are properly located in your cages will aid you in ensuring that your snake is properly heated. Regarding placement of stationary thermometers and/or where to monitor temperatures in the cage via remote probe placement or non-contact reading devices, there is only ONE place that matters. THE SNAKE’S BODY. No other place in the cage matters, so since we know that in the absence of eyelids to protect their eyes from UV light, and because corns are naturally nocturnal, the only place where you need to control temperature is inside the hide that is continually between 80°F and 85°F (26.7°c – 29.4°c), ideally; 81F to 84°F (27°c – 29°c).

UT (Under Tank) and OT (Over Tank) are the most common heeating methods used for corn snake Vivaria. We recommend UT heating, since it more accurately simulates how corn snake achieve proper body heat in the wild, and is the safest way to heat your snake. Yes, on cool days, wild corns will bask in light, but for most of the year, they achieve necessary body heat via lying on/near warm entities in their natural habitat (i.e. the ground or tree branches). Warming themselves from sunlight is safely achieved in the wild because snakes are able to move into or away from such radiation, depending on temperature tolerances. In cages–such as aquaria that have been converted to snake enclosures–heat from OT lighting (or OT heat-emitters) is impractical and inherently unsafe for several reasons. Because hot air rises, much of the heat output from OT heaters never reaches your snake, and nocturnal snakes like corns do not require (or appreciate) lighting in their cages. It’s inefficient in that most of the heat rising from the heat lamp or emitter is not getting down to your snake at the bottom of the cage. Therefore, often, snake keepers tend to use light or heat fixtures that emit more heat than the snake is comfortable (or safe) with. The resulting dehydration of the air space below the light or heat-emitter can contribute to dysecdysis (incomplete skin shedding) and even potential kidney damage. The very nature of such lights and heat-emitters is not focused enough to heat just one small space in the cage (the warm hide), the target of which is not only more economical, but safer for your snake. If not using thermostats to regulate the heat output of your particular heat source, if the surrounding room temperature spikes, your OT light or heat-emitter is still putting heat down to your snake, which could result in the death of your pet(s). “Passive” heating with UT devices is not only safer, more natural, and less expensive, but eco-friendly – via using less electricity. UT heaters are therefore much more widely used by corn snake keepers because the location of the UT heater beneath the bottom glass of the aquarium is focused on – and therefore heats – only one zone of the cage. Even if regulating devices like thermostats are not used, if the cage gets too warm, the snake can retreat to the cool end of the cage or in the water bowl, to reduce its body temperature. Insulating substrate materials like aspen bedding form a substratum that works as a buffer between the heater under the bottom glass and your snake. The temperature of the glass atop the UT heater can be as high as 120° F (48°c), but since corn snake virtually NEVER lie upon or near such hot surfaces, damage to your snake should not be a concern. Some snakes (i.e. Ball Pythons) eagerly burrow beneath the substrate and have been known to die from burns received from such hot surfaces. In the 45+ years I’ve been keeping corns – and having kept at least 60,000 of them – not one snake was ever burned from UT heating devices.

I recommend that the size of the UT heater never exceed 1/4 of the length of the cage. If too large, it’s possible to place the warm hide where it will overheat. If you already have a UT heater that’s too large, place the hide only partially above it. If the hide is too warm, the snake will opt to repose in cooler zones of the cage, thereby not achieving body temps necessary for appetite and digestion.

Whether using UT (Under Tank) or OT (Over Tank) heating, it is crucial to offer your corn more than one thermal zone within the cage – in order to facilitate successful thermoregulation. In most cases, exclusive use of a UT heating device is satisfactory, but even if OT heat emitters or lights serve your snakes’ temperature needs, they can sometimes be harmful to your snake. UT heat devices should be affixed to the underside of the vivarium, near one end only – NOT INSIDE the enclosure. Attaching a UT heater to the side of the vivarium is virtually useless, since most of the heat from that device will be dissipated into the room, instead of the cage. Bear in mind that the primary location in the cage that requires monitoring is INSIDE the warm-side hide — where your snake will spend the majority of its life in captivity.

In the absence of the ability to metabolically produce heat, thermoregulation is practiced by most reptiles to achieve comfort, metabolic efficiency, and basic survival. In a snake cage, this is accomplished by your snake voluntarily changing positions within the cage to facilitate their most important life functions; achieving appetite and digestion. In the wild, snakes that cannot find proper digesting temperatures are forced to leave their territorial spaces, but in a cage, if you do not provide adequate thermoregulatory resources, your snake has only one alternative (suffer starvation and consequent immune-deficiency). It is therefore your responsibility to provide at least two different temperate zones in your pet’s’ cages. Acceptable and safe digestion can be achieved in a cage with only one temperature zone, provided that one temperature is continually in the range of 80°F – 85°F (26.7°c – 29.4°c). Most professional corn snake breeders do not intentionally impose a night-time temperature drop, since constant maintenance of the 80°F – 85°F (26.7°c – 29.4°c) range results in more predictable growth rates and fewer digestive failures. We endeavor to maintain a constant 82.5°F (+ or – 1°F) in our snake buildings. In so much as most humans are not comfortable in a room that is constantly 80°F – 85°F (26.7°c – 29.4°c), for the casual corn snake pet keeper who maintains their reptiles in a room that is too cool for corn snakes, I recommend a cage with one hide that is 80°F – 85°F (26.7°c – 29.4°c) and one that is below 80°F (26.7°c). If either hide is not sufficiently and invitingly dark inside, your snake may not utilize those temp refuges, and may consequently fail to thrive. Corn snakes will know when they need heat and when they should avoid heat, so it is important to offer two temperate zones (and even a third, intermediary zone when possible). Be sure the heating device is associated with only one end of the cage so your snake can retreat to cooler zones in the unexpected event that the warm zone overheats. Without electronic controllers like thermostats or rheostats (both are usually not necessary), regardless of room temperatures, heating devices are fully ON or fully OFF (exception being proportional thermostats that delivery a constant flow of electricity to your heating device that results in one temperature point that was set by you). Given that electronic temperature controllers are subject to failure for many reasons, if using one, you should continually check the accuracy of such devices by monitoring temperatures on the warm side of the cage with one or two thermometers you trust. For this reason, we do not recommend thermostats or rheostats. They are additional devices that could contribute to the illness or death of your pet, should they fail. If one end of your cage is not affected by the heating device, the only way that end of the cage will be dangerous to your snake is if the entire room were to reach dangerously high temperatures – in which case a thermostat or rheostat will not help anyway. If you see your snake behaving uncharacteristically – if not from illness, parasites, or injury – it is sometimes the result of incorrect (and potentially unsafe) temperatures. Incidentally, another reason I don’t recommend the use of thermostats is that if they are not the expensive proportional devices, even if the probe is properly located (inside the warm hide), from the time when the probe cuts power to the heating device to the time it comes back on, the snake’s body temperature may drop as much as 4°F. Naturally, the inverse can also occur – temperature spikes of 5°F – 7°F until the thermostat disengages the heating device.

In most cases, the UT heater should warm less than 1/3 of the cage floor space (unless you are heating units in a rack system that has vastly less ventilation). Heating less than 1/4 of each cage in a rack system is recommended. Naturally, the end of the cage that includes the warm hide is the end you need to heat. In rack systems, heating either the inside back panel of the rack or beneath the back of each shelf is recommended. Using UT heating devices that are larger than 1/3 or 1/4 of of the cage floor can unintentionally heat more than one end of the cage, thereby not affording your snake with a cool refuge, should the warm end be unsafely warm. Since heating the underside of the back of shelves in a rack system obviously provides excessive heat to snakes beneath the shelves, it is recommended that you use proportional thermostats for rack systems. The option is to affix the heat devices to the inside back panel of the rack. Since little or no ventilation is afforded by most rack systems, heat buildup is a foregone conclusion. We put heat strips on the inside back panel of our racks routinely, since males can be rendered sterile if UT heating is excessive. Sperm are killed by such over-heating, so sterility is usually temporary, but in some cases males can be rendered permanently sterile from over-hearing. Proportional thermostats render steady heat levels to snakes, vs non-proportional thermostats that allow spikes at the end of each heat cycle.

HOT ROCKS are great for some diurnal lizards, but potentially dangerous for snakes, and should therefore never be used for ANY snake. Rare in corns is the potentiality that one will lie too near the hot rock and receive harmful contact burns. Unlike some serpent species (i.e. Ball Pythons and Boa Constrictors) that commonly injure themselves by bodily contact with hot surfaces, corns virtually always avoid such devices, but in doing so, will get sick from spending too much time in cooler zones of the cage.

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Don Soderberg 
South Mountain Reptiles
Canyon Lake, TX

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