Boa Constrictor Humidity Requirements

How to measure humidity

Humidity gradients with fluctuations are better than constantly being at a specific number. Why? 1) Fluctuations within a controlled range more accurately mimic nature and the conditions that an animal evolved to thrive in. 2) Brief periods of low humidity help prevent the development of potentially dangerous mold, mildew, fungi, etc. 3) It’s better for your mental health because maintaining humidity within such a narrow range is practically impossible and worrying about it will likely drive you to an early grave.

So how do you make sure that your boa’s humidity levels are correct? First, forget about the cheap stick-on analog humidity gauges that you saw at the pet store. It is very common for those to show the wrong numbers, which over time can make your snake sick.

Instead, monitor your humidity levels with a digital hygrometer (I prefer the Zoo Med Digital Thermometer/Hygrometer). They’re more expensive than the gauges, but they work much better, are easier to read, and will be far more useful in helping you create the best possible environment for your boa.

How do you make your boa’s enclosure humid enough?

There are several ways to boost your boa constrictor’s humidity (and keep it within the right range). Most keepers use one or more of the following methods:

1. Place a large water bowl under the heat source. This bowl should be large enough for your snake’s entire body and heavy enough not to tip easily because your boa will take the opportunity to soak. Some boas have a penchant for defecating (pooping) in their water bowl. It’s a pain, but it does make cleanup a lot easier. Make sure to disinfect the bowl with F10SC or Rescue every time before returning it to the enclosure.
2. Mix water into the substrate. This is a reliable method that mimics nature because the enclosure will experience cycles of humidity something like what happens after it rains. Simply keep an eye on your hygrometer and mix (don’t just pour) water into the substrate when it gets too dry. The substrate shouldn’t be muddy, but it should be damp afterward. For best results, use several inches of substrate.
3. Use a cool mist fogger. Fog regularly occurs in boa constrictors’ native habitat during the early morning before sunrise, and is a natural way to boost your enclosure’s ambient humidity. Plug the fogger into a timer and only use distilled/reverse osmosis water for best results. Foggers can be tricky to use, though — I recommend watching this YouTube video from Animals at Home for tips!
4. Use an automatic misting system. Misting in the early afternoon for 5 minutes with an automatic mister provides drinking water (you may observe natural drinking behavior via this method) and spikes humidity while still allowing enough time for heat lamp to burn off excess moisture before things start to mold/mildew. Keep in mind, though, that unless you’re going for bioactive, drainage is relatively poor in most enclosures, so misting periods will need to be shorter than the average precipitation cycle of South American forests. Keep a close eye on humidity levels and if it gets too damp, reduce misting time. You can also mist by hand with a pressure sprayer if you have the time, but most keepers find that this is simply too inconvenient for a large enclosure. The best automatic mister on the current market is the Mistking.
5. Create a humid hide. This is easily done by taking a reptile hide (made from a commercial hide, half flower pot, hanging pot liner, etc.) lined with damp sphagnum moss and placed on the cool end of the enclosure. Works great, especially when the snake is in shed.

Photo contributed by Rhonda Miller