Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Microclimates For Your Reptiles

Dealing with summer heat and low ambient humidity

©1996 Melissa Kaplan

Every animal has a preferred optimum temperature range (POTR), a temperature range in which its systems work most efficiently. On either side of that optimum temperature range is a narrow range of tolerable temperatures. Temperatures that are lower or higher than the tolerable range will cause stress and ultimately death. Animals also have less-well defined requirements for humidity and hydration. Chronic dehydration can lead to a number of health problems, including kidney failure.

Animals in their native habitat deal with abnormally high or low environmental temperatures by altering their habits in one of two ways. Diurnal animals will sleep or rest during the day, coming out at dawn, dusk or at night; crepuscular animals may come out a bit earlier or later. Animals will burrow under ground or under other shelter where the temperatures and humidity are less affected by the ambient surface and air temperatures. Many will aestivate (summer) or brumate (winter), which is a form of partial hibernation, wherein the animal rests for the duration of the overly hot, cold, dry or wet weather, conserving energy and fluids.

In captivity, an animal's options are greatly reduced. Within the confines of an often too small enclosure, and one set up without proper regard for its POTR. For example, iguanas, an animal with a POTR of 75-88, with a basking requirement of 88-95, will be kept at 75-85, or at 90-100. Box turtles, with a POTR of 73-85, will be kept at 70-75. Chinchillas, Andean mammals with super thick fur, are too often kept in outdoor enclosures during temperate summers, often succumbing to heat stroke when temperatures exceed 90-100 F. An enclosure, unless it is big enough to contain the necessary microclimates and those microclimates are actually provided, either regularly or as needed when dictated by changes in the ambient environmental temperatures, will not provide adequate retreat for animals, especially poikilothermic reptiles, reptiles who moderate their body temperature by behaviorally thermoregulating, by making use of sufficiently warmer or cooler, dryer or damper, areas in their captive environment.

Signs of brumation and aestivating include: attempts to burrow away in the coolest place in the enclosure; lethargy; loss of appetite; tonic rigidity or loss of tonicity; long sleep periods; failure to adequately rouse when disturbed; darkening of skin color (lizards).

Low Humidity
Many reptiles come from an environment that is mostly dry other than during occasional rains. The conditions above ground, however, may be quite different from conditions deep in undisturbed rocky crevices or underground burrows. There, not only are temperatures constant throughout the year, with very little fluctuation, but so too is the humidity level. Such crevices and burrows may themselves have humidity gradients, with the area closer to the opening to the outside world being drier than the area farthest away. In places such as these reptiles may maintain the necessary hydration when standing water is not available on a regular basis. These retreats may also assist them in getting through periods when prey animals are themselves laying low due to the excessive heat or drought.

Often, when snakes or lizards are showing signs of poor shedding due to their captive environment being too dry, owners seek ways to increase the overall humidity of the enclosure. While this is necessary for certain species, such as rainbow boas and tropical rain- or cloud-forest chameleons, overall increases in the ambient enclosure humidity may result in adverse health problems. Blister disease, and the growth of fungus and bacteria are not uncommon. Instead, microclimate pockets of higher humidity can be provided for most reptiles. For others, a slight increase in overall humidity levels coupled with bathing and spraying may be sufficient.

Increasing Ambient Humidity
For many small lizards and terrestrial chelonians, providing a large, shallow water bowl will raise the humidity. The water will more rapidly evaporate from the large surface area; the shallowness will reduce the risk of the reptile from accidentally drowning if they get into the water. For snakes or large lizards, deep tubs providing a large exposed surface area will work.

The ambient humidity in a reptile room or large walk-in enclosure may be provided by using one or more of the many inexpensive humidifiers that may be purchased at grocery and drug stores. These may be run 8-12 hours a day during the periods of driest weather, or daily, as needed.

Misting systems may be installed to periodically produce a fine mist from the top or sides of a large, well-ventilated enclosure. To get through periods of excessively dry heat (either in the winter or summer) spray bottles of water may be used to spray the reptiles and/or their environment. If your cages have sturdy screen tops, you can set up a gallon plastic bottle of water, such as water and milk come in, with small holes punched into the bottom. Spread a couple of layers of newspaper beneath the pierced bottom, or place a catch basin on the floor of the enclosure below. Let the water drip onto the branches or foliage in the enclosure on its way to the catch basin.

Humidity retreat boxes may be easily made by taking a plastic food or clothing storage container with a fitted lid. Cut a hole near the top of one side big enough for the lizard or snake to crawl into. Fill the box 2/3 full of damp sphagnum moss. Place the reptile into the box and place the lid on; they will find their way out of it. Thereafter, they will be able to enter and exit when they need to. Leave the box in the enclosure all the time, or place it in there in the middle of the thermal gradient, when you notice the reptile's color beginning to change as it enters the shedding period. Periodically take out the damp moss and dry it thoroughly before using it again. Re-wet it as necessary, keeping in mind that it will dry out faster in a warmer tank and when the ambient room humidity is low.

Drippers may be easily set up to drip into a screen-topped enclosure. An empty plastic ice cream container or milk jug can be pierced in the bottom with a fine instrument such as a dental curette. After making sure that the screen top will support the weight of such a filled container, place it on top of the screen. Place a catch basin underneath it on the floor of the enclosure. Potted plants, artificial plants or branches can be set under the drip. This often provides the play of water and light that many lizards require to be able to drink as well as the splashing help to raise the humidity of the enclosure. A dripper may also be made by getting a turn spigot from a hardware or hobby store. These are miniature versions of the spigots found on picnic beverage containers and beer kegs. Cut a hole the diameter of the connector of the spigot in the side of a plastic container near where the side of the container connects to the bottom of the container. Using an aquarium silicone glue, glue the spigot into the hole in the container. Once dried and cured, fill the container with water, turn the spigot on so that it begins a slow, single drop drip, and set it up on top of a screened enclosure as described above.

Providing Cool Spots
For summer cooling for reptiles, birds and mammals, fill a plastic bottle 3/4 up with water, put on the top, and freeze. To use this 'air conditioning', take the bottle from the freezer, wrap in a towel or piece of burlap, and place in the animal's enclosure. They can lay next to or near it, or even on it, to cool down.

Move the enclosure to the coolest part of the house; use thermometers to check temperatures around the house-you may be surprised by what you find. (Having trouble keeping an enclosure warm enough during the winter? Find a warmer place in the house in which to place the enclosure.) Increase the ventilation in enclosures (holes can be drilled in wooden/melamine tanks that can be covered up in cooler weather). Reduce the supplemental enclosure heating, either by turning one or more fixtures completely off and, if necessary, putting what heating remains on timers or dimmer switches.

Animals housed outside should not be in glass tanks; wooden tanks need adequate ventilation to ensure heat doesn't build up and remain trapped. Even sun baskers in open-mesh enclosures need a cooler retreat-not just shade.

The temperature ranges for any animal given in articles tells only part of the story. The animal's ecology, how it lives in and uses its environment, is the rest of the story. Read about this aspect of your animals' life in the wild to better understand what types of microhabitats are required.

Keeping Food and Water Cool
Indoors or out, keeping omnivore and herbivore food cool enough so that it doesn't spoil quickly in warm weather, can be a problem. A couple of ways to deal with this include:

Set the food bowl in a pie plate into which bags of ice have been placed.

There are food bowls made for human babies which are hollow to allow you to put hot water inside to keep the food in the bowl warm. Instead, 3/4 fill the space with water and freeze it.

Fill water bowls with water and freeze. Pop out the bowl-shaped cubes and store in freezer. If your reptile tends to dump his water during the day, placing a "bowl cube" in a bowl will mean he will have fresh water later in the day when it is warm and his regular bowl has already been dumped.