That's an interesting question, and I'm not sure there is a definitive answer.
What we
know is that BDs are considered arid-climate reptiles. They can get by on very little moisture/water, and excrete urate rather than urine. So their humidity should likely be drier than wetter (as humidity would be for a tropical reptile).
That said, for BD habitat, I like to look at the climate in Alice Springs, NT, Australia, because it's very close to the center of both the continent and the geographical range of BDs. The problem is, when looking for average humidity in Alice Springs, many different data sets can be found. Here are three:
http://www.alice-springs.climatemps.com/humidity.php
https://www.weather-atlas.com/en/australia/alice-springs-climate#humidity_relative
https://weather-and-climate.com/average-monthly-Humidity-perc,Alice-Springs,Australia
Also, because BDs have a broad geographical range, RH data can vary from point to point within that range.
From another perspective, internet and veterinary sources also differ on humidity ranges.
bearded dragon humidity
Looking at the first 10 (2 pages) links in the above search that had answers, values stated are:
35 to 40 percent
20-40%
30-40%
30-40%; nighttime 55-60%
35-40%
35-40%
Below 45%
50-60%
Same question asked on an Australian BD forum
http://www.australianbeardies.net/forum/archive/index.php/t-4050.html
35-40%
If you search the archives
here, you'll find literally hundreds of opinions, and you'll likely get a plethora of answers/opinions to this query as well.
In researching the above information, something I found curious/interesting is that
Reptiles Magazine, one of the accepted authorities on reptiles & reptile husbandry, has at least 8 articles on bearded dragons, and not one of the eight even
mentions the word "humidity" let alone suggesting/recommending any values. :? :? :?
So I'm not sure there
is a definitive answer. What I can suggest is pick one--or a range--and go with it.
I have a target range of 30-40% (Days) and less than 55% (Nights), and I have NO doubts others will have different opinions on this.
Let the Games begin! :lol: