>This question was posted on the Iguana Den board but it was suggested
that I post it here since not everyone here is a member there, I don't
The questions you raise here are bit to advanced for the general Ig
board except for the knowledgeable people that are on both groups.
I would highly recommend you read as much of the files section as you
can several times to get a grip on what you are seeking. The "ISS
article re edited" will answer a lot of your questions and Dr Gehrmann's
on "Comparison of two artificial light sources" as well will help.
There are just a very few (almost only one) bulb(s) on the market that
will give you sufficient UVB after 70% of the decay has expired.
I'm going to repost Fran's and my conversation from just a short while
ago to help understand the differences in reptiles needs.
That is a VERY good question. What species do you keep?
At the moment I'm not aware of any such chart, if there is one, I too
want to see it!
I think the general feeling at the moment is that herpetologists-
including us hobbyists - are actually pioneering this field right
now.... there is so little known, and blood testing of reptiles to
check their vitamin D status is still very much an experimental
phenomenon. Iguana keepers are a little ahead, because I guess the
creature is so big a blood sample is no big deal, and also MBD has
been so obvious a problem in this species that it has been researched
So far, various authors are suggesting that the best way to determine
how much UVB our reptiles need is to research what UVB they would
likely receive in the wild. This does not mean, find out the noonday
UVB for that part of the world, and stick it in the vivarium...
because that would be really unsuitable for shade-dwellers, those
that live in rainforest canopy and especially, crepuscular species
who may get little or no UVB in the wild.
Even desert dwellers often have early morning/late afternoon basking
habits and since the amount of UVB in sunlight is proportional to the
height of the sun above the horizon, amongst other things, only the
most sun-worshipping of reptiles will ever sit in full desert mid-day
sunshine levels(say 350uW/cm2) and even then, probably those levels
don't exist for more than a few hours in the middle of the day.
I've now seen several articles in which authors stress that we must
now consider providing what might be described as "UVB gradients",
like heat gradients, whereby our reptiles can move in -and completely
out- of the UVB and regulate their own UVB basking times. This seems
a natural enough conclusion! I think maybe (personally speaking) I
like the idea of providing my bearded dragons with at least one small
patch of "hot sunshine" around 200-300uW/cm2, since these do bask in
full sun during the day, in the wild. My dragons do sit in that
hotspot for small parts of the day; I've noticed they tend to hang
around longest in the 50-150uW/cm2 zone, though, but I haven't done
any serious recordings of their behaviour yet....
I've been trying to find data myself and so far I have found studies
with data on Chuckwallas, Chameleons and Green Iguanas.
The Chuckwalla study suggests that Chuckwallas choose to bask in
areas of high UVB exposure (as high as 383uW/cm2 was noted) for part
of the day when this is available to them.
The Chameleon study addresses egg hatchability in Panther Chameleons
and suggests low levels of UVB (a gradient between 5-15uW/cm2) are
optimal, however another writer suggests that levels similar to those
found in the wild chameleon's habitat (a gradient between 50 -
100uW/cm2) are more suitable. High levels are seen to be harmful.
Iguanas appear to have requirements - and behaviour patterns -
somewhere between the two. One author recommends keepers of green
iguanas to make levels of at least 30-50 uW/cm2 available to their
animals, and another study indicates that an absolute minimum of
10uW/cm2 is required at a basking site, and a gradient of 20 -40
uW/cm2 is optimal; these levels would all be around the minimum
level a wild iguana would experience during the day, whilst in the
Few snakes or amphibians, or nocturnal/ crepuscular lizards such as
geckos, are thought to require ultraviolet lighting, at present, and
authors suggest that dietary vitamin D3 may be adequate for most
species. However, Diamond Pythons are known to require UVB in
captivity. Snake eyes appear to be sensitive to too much light, (not
necessarily just UVB, though) and so as with the other reptiles, they
must be able to find shelter from light and from UVB if it is used.
The main articles are:
1. Aucone B.M., Gehrmann W.H., Ferguson G.W., Chen T.C., and Holick
M.F. 2003. Comparison of two artificial ultraviolet light sources
used for Chuckwalla, Sauromalus obesus, husbandry.
2. Ferguson G.W., Gehrmann W.H., Chen T.C., Dierenfeld E.S., and
Holick M.F. 2002. Effects of Artificial Ultraviolet Light Exposure on
Reproductive Success of the Female Panther Chameleon (Furcifer
pardalis) in Captivity. Zoo Biology 21:525-537
3. MacCargar, R. Iguanas and Artificial Ultraviolet Light: How and
How Much Made Simple - Well, Not Exactly Simple. 2003. Journal of the
International Iguana Society 10 (3) 82. -now fully revised, 2004.
I'm typing this offline so I can't check, but I *think* these are all
in the Files section?
Hope that helps!
This is excellent writing! (Looks like something the Info site should
pirate) Normal natural habitats UV, the reptiles natural habitats, and
having an understanding of the amounts of UVB in different shaded areas
such as the difference between reflective qualities of sand and stones
as compared to greenery and or water basins would also need examination.
Some noted information centers constantly bring up the fact that green
iguanas spend much of their time in the shade during mid day and
therefore aren't exposed to much UVB. While it definitely is true that
iguanas as well as most basking reptiles spend the hotter portion on the
day in the shade, it's also a fact that readings of 50-300uW can be
registered in the shade (while direct sunlight is at 350-450). It would
be difficult for this species to be exposed to less then 50uW from 8AM
As you mentioned, few creatures would spend any length of time in the
higher levels of UVB. And although Gehrmanns study exposed spiny tailed
iguanas to 380uW to get the OH25 blood serum levels that matched normal
wild levels, I suspect that 6 hours a day of 250uW/cm2 would have had
the same results. Remember the chucks were chosen because they would be
a good cross example of desert reptile species.
Chameleons are a difficult species for me personally to figure out and I
have had to change my standing on UVB recommendations. Gary Fergusons
teams work indicates that chams (panther species at least) are best at
about 10microwatts. In the wild it is logical to realize that chams
would be exposed to much higher levels of UVB at least part of the time.
Readings here in NC USA have shown that even in the deepest bushes when
there is 250uW in the sun, it's very difficult to get readings under
10uW. When its 350-400uW in the sun it becomes even more difficult to
get low numbers such as 10-20uW.
Just how often is it a bright sunny day in the chameleon species in
question natural setting though? Rain fall in Madagascar, where the
Panther chams originate, varies from tropical rain forest to desert
conditions. The east coast of the country can get up to 118 inches
(3000mm) a year. There are free ranging breeding colonies of Jackson
chams in S Florida and Hawaii where it doesn't get any where near as
much rain or cloud cover. I have seen many pictures of chameleon
breeders in Florida and Arizona using outside habitats, and it's easy to
see that these creatures are exposed to much higher then 10uW at least
some of the day.
I have heard of many chams that were not doing well under low level UVB
(10uW) and had complete turn a rounds when given the ability to be
exposed to up to 50uW (with UVB gradient off to 0uW). Keepers have sent
me pictures of the results. To contradict this I have also heard of
chameleons have physiological problems due to the higher UVB exposure
such as from your friend Rob. I personally have seen conjunctivitis in
chams exposed to higher numbers, 75-100uW. Neither the good results nor
the bad results can be ignored.
To err on the side of safety would seem the logical choice. Unless there
is a reason to increase the levels of UVB for a cham not "doing well"
under traditional UV tube lighting, the lower numbers such as 10uW to
possibly 30uW with gradients to 0uW would be my suggestion at this time.
Speaking of "UVB Gradients", in my rehabilitation (iguanas) work I find
the observation that creatures that have been UVB starved will spend
almost all of the 12 hours of light directly under the Mega-Ray flood.
(I just had three iguanas come from out of state over the last three
months that fit this category well) These lamps all produce 150-250 (or
higher depending on the condition of MBD) at the basking area meaning
that the animals are exposed to 150-250 microwatts for most of 12 hours
only spending time away from the UV during feeding and looking for ways
to get out. My family creatures that have had great UVB for years will,
as you said, will be on the outside of the UV circle under 75-150uW.
This is how I came up with my recommendation of these numbers of 75-150
microwatts for most basking UVB dependent reptiles.
In the end I believe that we will be able to group species and UVB
recommendations even to the point of a few microwatts for a few minutes
for your crepuscular species such as the gecko species. I really love
As a side point. You mentioned that mid day readings of "350". The high
readings can be as high as 450uW. Here in NC USA, I get readings over
400 during the summer months and as little as 75uW/cm2 in the winter
with bright sun shine. This is with the US standard of measurement. The
European's measure the UVB spectrum at a bit of a lower number stopping
at 315nanometers instead of 320nanometers. The closer to the equator,
the less variance in UVB readings during the seasons as well.
Unfortunately Fran, I feel that only dedicated herpetologist and
hobbyist will ever look for these findings in fine tuning their
I am hoping that with your and Dominick's writing skills, this kind of
information can be posted on the Info site as a reference that all can
Best to all,
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