Humidity and Captive Herps Christina Miller Last update: Monday, December 31, 2007.

The health of your pet reptile or amphibian will be a product of the environment that you provide them, and humidity is an important aspect to consider when designing and maintaining a suitable enclosure. Inappropriate humidity levels can cause disease and the eventual death of your herptile.

Humidity and health

It is vital to realize why appropriate humidity is important. Reptiles mainly regulate their body's water content by drinking and eliminating (urinating), but a small amount of water regulation is carried out by the skin and respiratory surfaces in the lungs. Different species' bodies have adapted to survive in the particular conditions that they live in: Herps are not very adaptable creatures. If a herp is kept in conditions that are not humid enough, the herp will constantly be losing small quantities of water when it expirates (exhales) and through its skin. These water losses can cause dehydration that varies from mild to severe. Very severe dehydration in reptiles is very rarely caused by environmental problems (a severely dehydrated herp is almost guaranteed to have some underlying health problem), but mild dehydration over years of being kept in suboptimally humid conditions can certainly cause chronic problems (such as renal insufficiency). On the other hand, keeping a herp in conditions that are too humid can lead to acute respiratory and skin problems.

Amphibians are more dependant on humid and wet environments than reptiles, making them more sensitive to humidity problems. They naturally regulate their body's water balance through their moist, porous skin, so both gains and losses can be caused by the environment. Amphibians should never be left without a clean water dish because of this.

How much humidity?

Humidity requirements vary greatly between different species of herps that come from different habitats. For humans, 50-70% humidity is considered normal, whereas above 70% is high (humid), and below 50% is low (dry). However, reptiles and amphibians are not humans, and depending on the species, their humidity needs and preferences often are very different from ours.

How do you find out what relative humidity a certain species requires? Do your research! Unfortunately, there is a lot of conflicting care information available for many species. Consult reliable sources like well-reviewed books, websites from credible sources and veterinary practices that are experienced with herp care and medicine.

Ideally, every enclosure should have a hygrometer- a device used to measure humidity. Hygrometers display a percentage from 0 to 100. This is the percent of water vapour in the air.

Hygrometers come in both digital and analog varieties, and while product quality varies between different brands, digital hygrometers are certainly more accurate and reliable than analog ones. There are many thermometer/hygrometer combos available for both home use and for pet use. You will find that those not designed for use with pets are usually cheaper in price, however they are not always appropriately sized or designed for all applications. Often those designed for pet use have some kind of attachment like Velcro or two-sided tape so that they may be affixed inside the enclosure. Units with a remote sensor (probe) are very useful for animals that are very active or destructive in their enclosures, so that the expensive instrument can be kept outside of the cage.

A general rule of thumb: Desert species need low levels of humidity (at least below 50%), forest species need higher humidity (60% or higher). Of course, it is important to properly research the needs of your pet before purchase. These are not the only two habitats that reptiles and amphibians live in, and microhabitats within a herp's habitat can have drastically different conditions than the majority of the area. Microhabitats and their importance will be discussed later.

Controling humidity in the enclosure

If humidity is going to be monitored, then it must also be controlled. Humidity is not a constant phenomenon in nature, as it fluctuates seasonally and even daily with weather changes. Think of how humid and muggy it feels outside after a summer rain, compared to a cloudless sunny day. When considering your herp's enclosure, humidity does not have to be at a constant percentage either, however guidelines for the species must generally be respected.

To increase humidity:

• Frequent misting with water (either manually with a spray bottle, or with a programmable automatic sprayer)
• A wide water dish with a large surface area allows for more evaporation; placing the water dish over an undertank heating pad or under a light will enhance evaporation (make sure the water never completely evaporates)
• Add an airstone ("bubbler") to the water dish
• Foggers and humidifiers can be very effective
• Natural substrate like an organic forest mix will hold more humidity than sheet substrate like paper towel or carpet (only if particulate substrate is a safe alternative for your pet)
• Add live water-loving plants either in their own pots or planted directly into the substrate
• Cover some of the enclosure's ventilation (ex: screen or mesh lid) with plastic

Note that ventilation should never be fully compromised to increase humidity. Fresh air is extremely important to reduce unhealthy bacterial and fungal growth in the enclosure, preventing the atmosphere inside from becoming stagnant. Although high humidity levels are important for certain species, a very humid enclosure must be kept exceptionally clean because increased heat and humidity can encourage bacterial and fungal growth. Microbes are not necessarily "bad," as they are naturally found everywhere in controlled numbers. But, if the environment encourages microbe growth, and some potentially dangerous species happen to flourish, it can be problematic for both your health and the health of your pets.

To decrease humidity:

• Only mist as often as necessary if the animal drinks from water droplets
• Keep water dishes small
• Ensure the enclosure has appropriate ventilation
• Avoid using devices that create water movement, like waterfalls and airstones
• Use false plants instead of live, or live plants that tolerate drought well
• Add a computer fan on a timer near one of the ventilation ports of the enclosure (ensure that the sound of the fan does not disturb the animals)

Microhabitats

Wild herps have huge environments containing many smaller microhabitats, which are small localized areas that have conditions (light, heat, humidity, etc.) slightly different from the immediately surrounding environment. It is widely known that herps will thermoregulate within their habitats, but it is also thought that they may hydroregulate, as well. In burrows, crevices, under leaf litter or inside dense foliage definitely demonstrates different conditions than the surrounding areas, and these differences are often neglected in captivity.

Most caresheets only recommend providing humid microhabitats, often called "humid hides" for only a handful of species. They are most often quoted as a necessity for species that live in arid habitats, and they are required to help the animal shed its skin. However, it is ideal to provide several different microhabitats to any herp so that they may pick and choose accordingly. Hydroregulation is certainly not restricted to animal that live in dry regions. Humid microhabitats that you provide can range from anything between live plants, to moss under a bark slab or a plastic food container filled with damp paper towels. As long as it is safe, accessible to the animal and easy to clean if soiled, it can work.

Leopard Geckos (Eublepharis macularius) are a species traditionally required to be provided a humid hide to aid with ecdysis.