Bearded dragon substrate, humidity, and diet.
Inspired by @kaijutegu's recent post, let’s talk about calcium sand.
So, calcium sand, and substrate in general, has been attributed to impaction in bearded dragons (and other reptiles, but for this post, we’re just focusing on dragons.) However, while some substrates are more natural choices than others, and as such are more digestible, substrate itself is typically not the root cause of impaction. Improper husbandry such as dehydration, improper lighting, diet and supplementation all negatively impact the digestive system as well as the body in general, and the problems only compact when these factors are stacked together.
Firstly, lets look at a bearded dragons natural habitat. This video courtesy of the veterinarian Jonathon Howard, known online as the Beardie Vet, shows the texture of the substrate that wild dragons live on. The sand is loose on top but packed underneath. The grain size is about 96% fine sand.
Next, lets look at this map.
This map courtesy of Claire Jaworski overlays wild bearded dragon sightings from iNaturalist over a soil composition map of Australia. Note how many of the sightings are found in Calsisol zones. Calsisol (also known as calcarosol) zones are characterized by containing 15% or more calcium carbonate. We know that bearded dragons engage in geophagy, or intentionally eating substrate. This is likely a natural behavior that they would perform in the wild to fulfill their biological need for calcium. We provide calcium as a supplement so that they do not perform this behavior in captivity (however this is not the only vitamin we should be providing!!!)
Next we should consider humidity, as there is not much standing water in their natural habitat, as well as diet, which they also obtain water from.
Contrary to popular belief, the natural habitat of bearded dragons has a very wide range of humidity, both throughout the day and throughout the year. When they are found basking, the humidity typically ranges between 10-30%. However, the morning after rain can be around 60%.
According to these maps, which measured the humidity of Australia over the course of 30 years, many dragons would be found in areas that range between 50-70% humidity in the morning and 20-40% at 3 in the afternoon.
It is also important to note that dragons are frequently found in burrows when not out and about. In these burrows, the humidity can be higher than the surrounding air.
As far as diet, this entire post is just a fantastic resource, again, courtesy of the Beardie Vet. In the wild, adult female dragons would be ingesting 48% plant matter in their diet, with males ingesting 68%. As far as moisture content, “Most plants/herbs are around 85% water – herbage 80% water, flowers observed eating >90% water; Insects are about 65% water – Termites 60% water, crickets 67% water.”
Bearded dragons, while they do not spend a lot of time drinking, are dependent on both the natural humidity cycle and their diet to stay hydrated. It is not natural to maintain a humidity of 30% or lower all year round, and compounded with poor diet and lack of access to water, can lead to dehydration, which in turn disrupts the digestive system’s ability to do its job.
So let's bring it back. Bearded dragons are naturally found on substrate with calcium in it. If you look at Zoomed or Fluker’s calcium supplement, for example, you will see that they are calcium carbonate. If you look at the ingredients for T-Rex, RepTerra or Komodo’s calcium sand, all are made with the exact same calcium carbonate.
So what’s the problem? The problem is, in the absence of poor husbandry, the ratio. Remember that Calsisol is 15% or more calcium carbonate. Well, most bags of calcium sand are 100% calcium carbonate. They should not be used straight, instead mixed together with other safe substrates such as children's play sand, excavator clay, and pesticide and fertilizer-free topsoil to create a natural and safe substrate mixture. The proper substrate will not only allow them to create burrows like they would in the wild, it will allow females a safe place to lay eggs (which they can do even without the presence of a male), help retain heat, and keep humidity at normal levels, as well as provide natural enrichment.
Thank you for reading.
