Humidity - Making Sense of Nonsense

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Such and such reptile needs a humidity level of XX%.

How many times have you read/heard that?

How many times have you wondered just exactly what this statement means?

Well, the person who wrote it probably doesn’t know. Actually, to be exact, the person who wrote it probably doesn’t understand exactly why humidity is important to ectothermic/poikilothermic creatures.

Then again, maybe they do.

When we speak of humidity, we are referring to relative humidity which is denoted as a percentage. Relative humidity is defined as the percent of saturation of air with water vapor.

Warm air has a higher capacity for holding more water vapor compared to cold air, therefore the relative humidity will rise and the temperature falls (and vice versa).

We are all familiar with what “dew point” means – right? In temperate climates during the summer, night time temperature drops result in atmospheric water being deposited as “dew” on vegetation. This happens because the cooler night air cannot old onto the water vapor it held during the day.

Now hold onto this concept because it is critical to understand it when keeping captive reptiles.

Most reptile keepers keep their animals in enclosures where the ambient temperature is much higher than that of the surrounding room. This means that more water is needed to be introduced into the habitat to maintain moderate to high levels of humidity.

How that water is introduced is key, as is understanding the microclimate of the species that are being kept. Most diurnal reptiles are active during time of the day when relative humidity is high and then seek shelter during the hotter periods of the day.

These shelters often include underground burrows, leaf litter, rock outcroppings, etc. which all are locations that have both cooler temperatures and relative high levels of humidity.

Ever stop to think about the humble termite mounds that many species of snake utilize? Did you know that they are usually oriented in a north-south direction so that they absorb as much heat as possible around dawn and dusk while also minimizing heat absorption in the middle of the day?

Tropical reptiles will lose substantial body heat during evaporation and therefore need to expend higher levels of energy in order to thermoregulate in drier conditions.

Manual misting with a hand held sprayer is never really effective – mainly because it is near impossible for keepers to properly schedule the natural cycles of high nighttime humidity that are the result of naturally dropping temperatures after inputting water during the day.

It is of utmost importance to cycle the relative humidity on a daily basis – high at night/low at midday) to properly maintain the health of many captive reptiles.

In Tupperware tubs - replete with their requisite newspaper substrate (to avoid those well-known but never experienced substrate impactions), the deli cup water bowl, the two symmetrical hides, and the perfectly maintained strip of flex watt belly heat that never fluctuates - this cycle becomes almost impossible to replicate. Keepers are then forced to pull out their little misting bottles and spritz the crap out of their tubs every day.

Besides being fairly ineffective, the introduction of heavy doses of water in a closed system with little to no circulation carries a substantial list of health risks. I mean, aren’t newcomers to the hobby regularly told to restrict air flow into ball python enclosures along with spritzing to increase humidity? Stop and think how this may adversely affect the health of the animal….small closed environment, lack of air flow, high humidity, traces of fecal matter………

So what’s the best solution?

For animals like varanids and heloderms, I have always utilized misting systems that are timed to go off when the heat gets dropped for the night. The substrate and enclosure surfaces are still warm, the water is introduced into the system and during the night relative humidity will jump from about 40% to about 65%. Them ambient night time temperature of the enclosure is set to that of the snake house. In the morning, lights go on and the enclosure is gradually warmed and the “dew” begins to slowly evaporate, which in turns naturally and gradually maintains stable humidity levels until the high heat lamps switch on. When this happens, the animals can escape the heat by utilizing hides or burrowing.

For high humidity snakes that are not in planted enclosures with misting systems and night drops (read Tupperware tubs) I use humid hides. These are easy to make and regardless of whether the animal is diurnal or nocturnal, provide an elective humid retreat.

Heating cold winter air and cooling warm summer air both reduce the relative humidity of air. This is why the use of humid hides is so much more effective than spritzing in rack systems.

So next time someone tells you to block airflow, spritz and repeat…think instead of what relative humidity is, how it occurs and how to safely meet that requirement in whatever set up you are utilizing.