Herptiles.net - Heating Your Herp

Heating Your Herp Christina Miller Last update: Tuesday, February 5, 2008. Most illnesses in captive reptiles and amphibians are directly related to poor husbandry. Incorrect enclosure temperature is usually one of the culprits. Considering that bodily functions such as immunity and digestion are related to body temperature, it is no surprise that a herp kept too hot or too cool will develop some type of illness Ectothermy: The true "cold-blooded" All reptiles and amphibians are ectotherms, which literally means "heat from outside." Ectothermic animals are those that cannot generate their own body heat, so they must rely on their environment to regulate their body temperature. This differs from endotherms ("heat from inside"), like mammals and birds, whose body temperature is mostly a result of their metabolism generating heat. Compared to endotherms, our ectothermic herps have slower metabolisms that do not generate much heat, and their bodies are less efficiently insulated to keep in the heat that is produced (they lack fur or feathers). An animal's body temperature can be determined with the following equation:: Heat produced by metabolism + Heat gained from environment - Heat lost from environment = Body temperature

All animals have a particular temperature that is needed for their body to function properly. Homeostasis is the body's effort to keep its internal conditions stable, and thermal homeostasis is how the body keeps itself at the correct temperature for physiological processes to work. Every ectotherm has a preferred optimal temperature range (or "POTR"), which is a range of temperatures that the animal's body will fluctuate within to aim for the one perfect temperature needed.

Thermoregulation is how an organism will achieve its body's optimal temperature. Humans, for example, will sweat when they are hot and shiver when they are cold, which is an example of physiological thermoregulation: The body will do this without conscious thought. To maintain its body temperature within this range, reptiles and amphibians mostly apply behavioural thermoregulation. An ectotherm that thermoregulates behaviourally will move from warm to cool if its body temperature is too warm, and from cool to warm if its body temperature is too cool. Because there are so many microclimates in a herp's habitat, there are almost always places that differ in temperature. For example, some animals will bask on a sunny tree branch to warm themselves, where others will burrow themselves below sand or earth to escape from the sun's heat.

Many herps also utilize physiological thermoregulation in addition to behavioural. Many species will change colours to better absorb or relfect heat, a phenomenon called albedo. Amphibians will regulate skin moisture to help evaporate excess heat, which can be compared to mammalian sweating. (O'Malley 2003) There are also many species with ornamental spines, crests and flaps, which could act as heat-absorbing or dissipating surface areas.

Most herps are heterothermic (or poikilothermic) ectotherms, which means that their body temperatures have a relatively wide range. There are a few homeothermic ectotherms whose bodies' fluctuate within a very small range. Most mammals are homeothermic endotherms, meaning that their body temperature is regulated from within, and it remains relatively constant. Hummingbirds are an example of heterothermic endotherms: Their body temperature is regulated from within, but their drastic shifts in metabolism causes a relatively large temperature difference between periods of activity and periods of rest. (Calder 1971)

Thermal gradients

Providing a temperature gradient in captivity is essential for the health of your reptile or amphibian. Without a gradient suitable to the species you are keeping, the animal can neither warm up nor cool down properly, which will results in serious, if not life-threatening health problems. Setting up a proper thermal gradient is not as complicated as it may seem, as long as a few key points are understood.

Gradients are not one-dimensional. The temperatures within your animal's enclosure should change from the top to the bottom, from one side to another. This creates a horizontal, vertical and consequently, a diagonal gradient. Of course, the gradients are not literally from "hot" to "cool," these words are relative to the species' preferred temperature range (i.e.: a tropical lizard with a basking spot of 40°C is not going to need a cool zone of 12°C, whereas 40°C would be too hot for an animal from a temperate region).

The area in the enclosure with the highest temperature should be near the primary heat source, which could be a ceramic heat emitter, a heat lamp or an under tank heating pad, depending on the needs of the animal you are keeping. A secondary heat source in the cooler part of the enclosure may be necessary if the minimum temperature of the suggested gradient for the species is not reached. Also, nighttime heat sources (not light sources) may be necessary so that the enclosure does not fall too cold at night, especially in cooler climates and during winter.


How "powerful" the heat sources you use depends on many factors, including regional temperature, season, what area of the house the enclosure is in, what the enclosure is made out of, etc. For this reason, you cannot suggest a specific wattage for your animal's heat sources. You must compensate for the ambient room temperature and time of year by changing the strength of heating devices in the enclosure when it is needed (for example, you will likely be using a higher wattage for a heat lamp during winter than you would during the summer). This also means that before introducing your animal to its enclosure, you must first test and decide on what wattages will give you the temperatures your pet requires to stay healthy.

Preferred Temperature Ranges For Common Pet Reptiles (excerpt from Reptile Medicine and Surgery, D.R. Mader) Species Day (°C/°F) Night (°C/°F) Ball python (Python regius) ~30/mid-80s 21-27/70-80 Boa constrictor (Boa constrictor) ~30/mid-80s 21-27/70-80 Corn snake (Pantherophis guttatus*) 25-29/77-84 19-24/67-75 Giant green iguana (Iguana iguana) 29-32/84-90 19-25/67-77 Leopard gecko (Eublepharis macularius) 25-29/77-85 18-24/65-75 Semiaquatic turtles, most species 27-29/80-84 18-21/65-70 Heating Devices Incandescent light bulb: Inarguably the most commonly used light source, the incandescent bulb is suitable for many heliothermic (species that warms itself by basking) lizards, snakes, and turtles. Be careful to use ceramic sockets instead of plastic, if the socket is plastic it will risk melting to the metal part of the bulb, rendering the socket useless. It is cheap (as long as you do not buy the "special" basking lights "for reptiles," they do the same any other one of equal wattage), and a high wattage emits quite a large amount of heat. While it is good for most reptiles, most amphibians will not fare well underneath these, the heat can easily dehydrate them even when shade and a constant source of water are not provided. . Ceramic heat emitter (CHE): CHEs are to be screwed into a socket much like the incandescent bulb (this absolutely requires a ceramic socket, plastic would melt) it heats the animal/objects in the enclosure, not the air. This would make it ideal for open-air wire enclosures, and great for nighttime heating as they emit barely any light. They are expensive, but they are supposed to last for up to six months. . Hot rocks, branches, caves: In many pet shops you'll see shelves full of hot rocks, heat branches, warmed caves, all with pictures of reptiles perched happily on top of them. Hot rocks should NOT be used as a primary heat source, regardless of how safe the manufacturer claims the product is. Hot rocks are dangerous for your pet, too often will the internal thermostat wear out, and the unsuspecting reptile will be cooked from the belly, up. . Some people assume that if the reptile is too warm, it will just move off of the rock. However, this is a very dangerous assumption: Reptiles do not have as many heat sensing nerves on their undersides as say, people do on their hands. They simply cannot feel that the heat is radiating from beneath them, and not having a very complex intelligence they will not necessarily move. By the time the animal is able to feel the heat, it is often too late and the animal's underside is seriously burned and its insides partially cooked. . These are also fire hazards, stories circulate about owners who buy the more expensive (assuming it would be of better quality) ceramic hot rocks, only to find that it cracked when water splashed on it, revealing the inside wires and element. Wrapping the rock in a towel is not recommended, it is a fire hazard. In short, hot rocks are safer to be not used at all. . Under tank heating pads: These come in a variety of sizes and stick to the bottom of the enclosure. They do not heat to outstanding temperatures like hot rocks and work well to heat amphibian enclosures; many come with a thermostat. These are useful for thigmothermic species (animals that absorb heat from another object which was warmed by the sun). . Underwater heaters: If your aquatic or semi-aquatic reptile or amphibian's water is not warm enough, you may choose to use a glass, underwater heater. Be sure to hide it completely behind cage furniture so that it cannot be disturbed (it gets hot! Do not allow your herps, or your fingers, to get near this while it's plugged in). If you have a set-up with large animals that can easily move around the cage furniture, use silicone to keep the furniture in place, or use an under tank heating pad instead (if the animal is semi-aquatic, direct an incandescent bulb at it's basking spot. The ambient temperature inside the enclosure may be enough to keep the water warm enough). Last modified: Monday, January 5, 2004 . Sources: Calder, CA. 1971. Temperature Relationships and Nesting of the Calliope Hummingbird. The Condor , Vol. 73, No. 3 (Autumn, 1971), pp. 314-321. Rossi, J.V. 2006. General husbandry and management. In: D. R. Mader (ed.), Reptile Medicine and Surgery, 2nd ed. Saunders Elsevier, St. Louis, MO. Zug, G.R. 1993. Herpetology: An Introductory Biology of Reptiles and Amphibians. San Diego: Academic Press.