Infrared - sunlight vs. basking lamps

lilacdragon

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Hi, guys.
In a long discussion in another thread, ( http://www.tortoiseforum.org/thread-83263.html ) on the causes of pyramiding, the subject of basking lamps came up. A question was raised about my comment that short-wavelength infrared was vital for basking, but there were additional concerns with artificial lamps vs natural sunlight. As the discussion on that thread has continued into nutritional concerns, I'm posting about infrared separately, here.

The infrared story is very interesting. It is something I only started looking at in the last year or two and it all ties in really well with the UVB story, and it is quite theoretical. Basically, it is to do with the interaction of sunlight and water.

"Sunlight" is arbitrarily sub-divided by scientists into UV, Visible, and Infrared wavelengths.
Infrared is subdivided by scientists into infrared-A (IR-A, 780–1400 nm) and infrared-B (IR-B, 1400–3000 nm) and infrared-C (IR-C, 3000 nm–1 mm).

The infrared wavelengths of sunlight are almost all in the shorter wavelengths called IR-A. There is a small amount of IR-B but no IR-C.
IR-A wavelengths are very close to red light, and indeed they work very much like red light; they can go through the skin and penetrate deep into the body. Think how, if you shine a bright torch against the back of your hand in a dark room, you can see the red light coming through your palm. IR-A will gently warm through the entire body of a small reptile as it basks. Bigger ones will of course take a lot longer to warm up.
There is something special about the IR-A from sunlight, though, that needs mentioning.
Our earth's atmosphere contains a great deal of moisture - water vapour and droplets - in the miles of atmospheric gas filtering the light from the sun. Water absorbs very specific wavelengths of the sun's radiation. When it absorbs this energy, it warms up. The wavelengths in the IR-A region that are absorbed by water can be detected very easily by looking at a spectrum of sunlight, in the IR-A region. Where the water has absorbed the IR-A, it is in effect "used up", and so is missing from the spectrum; so you can see a big dip in the irradiance at this point. Here is a solar spectrum as it is in outer space (the yellow blocked-in part) and how it is on the earth's surface (the red blocked-in part) and you can see the big dips taken out of it by atmospheric water vapour, which are labelled (Hâ‚‚O):

600px-Solar_Spectrum.png

(Image created by Robert A. Rohde / Global Warming Art
http://www.globalwarmingart.com/wiki/File:Solar_Spectrum_png)

I'll explain why this is important later on.

But the sun also warms the substrate, rocks, trees etc. Objects warmed by the sun re-radiate this heat in the longer wavelengths (IR-B and IR-C) that are also invisible, but can often be felt - hold your hand just above a hot sun-warmed rock and you will feel the long-wavelength heat as a prickly warmth on your skin. This long-wavelength infrared doesn't go deep. It hits the surface of the skin and immediately gives up its heat energy to the skin surface. It will warm the surface very fast, but the heat will need to warm deeper layers by conduction, a much slower process.

Indoors, we create IR-A with basking lamps (incandescent light bulbs, halogen bulbs, mercury vapour lamps and metal halides). Heat sources that do not also give off light, such as ceramic heaters, heat plates, and heat mats emit mainly longer wavelengths - IR-B and IR-C.

So it makes sense to use non-light-emitting heat sources for warming the air and the background environment, in the way that warm air and warm soil throws back heat after the sun has been on it all day.... In cooler northern climates, we typically place these to provide suitable ambient temperatures in areas that the tortoise will move around in when not basking.
And then we use basking lamps emitting visible light and IR-A when we are providing "sunlight" for basking species, and it makes sense to hang these lamps above the tortoise, like the sun.

But now we have to consider the difference between the infrared from a basking lamp and the infrared from natural sunlight.

This graph shows the spectrum of a halogen lamp (in red), so that you can compare it with the solar spectrum (in green).

MH-halogen_spectrum_plot.jpg

from: http://3dprinter.wikidot.com/dlp-projectors-optics

You'll notice that the halogen lamp doesn't have the big dips in its spectrum, caused by several miles of water vapour and droplets taking out the energy from those wavelengths. The halogen lamp also has a lot more IR-B than sunlight, and it also has some IR-C. So when the tortoise basks under a basking lamp, he gets ALL the IR-A wavelengths, including the wavelengths that are missing from the sunlight, plus some IR-B and IR-C.

But the IR-A wavelengths missing from sunlight are the wavelengths that are most readily absorbed by water molecules. Since the lamp is at most, 1-2ft above the tortoise, not several miles away, there cannot ever be enough atmospheric water vapour between him and the lamp to absorb those wavelengths. So where are the first water molecules those wavelengths encounter? ... inside the cells of the tortoise's carapace and skin! These immediately absorb the energy from those wavelengths of IR-A... creating heat in the carapace and skin.

The other IR-A wavelengths penetrate deeper and release their warming energy through all the body tissues, but these "dump" all their energy into the water inside the very top layers of skin and keratin....
And so do the IR-B and IR-C wavelengths.
This sounds like it might well be a problem for parts of the body evolved to receive mainly sunlight, which has little or none of these wavelengths present...
I would love to know whether it is an important factor in pyramiding....

There is a growing use of red and infrared light in healing of wounds and stimulating the body's repair after injury, in human and veterinary medicine. Red lasers are mainly used, but a new technique using "water-filtered IR-A" is being pioneered by some German people and it looks very promising.
For example: "Water-filtered infrared-A (wIRA) in acute and chronic wounds"
The idea is to have a thin layer of water in a special tray inside the lamp unit. It is terribly expensive and totally impractical for us as keepers, but it does look interesting. Here is something I just found on Wikipedia, showing a spectrum of "water-filtered IR-A" - see how the water is removing quite a large amount of those "water" wavelengths from the halogen lamp spectrum, and how there are other filters which remove the longer-wavelength IR-B and IR-C, too.

WIRA-Wiki-GH-017E-en-Spectra-wIRA-sun-halogen-radiators.png

From: http://commons.wikimedia.org/wiki/File:WIRA-Wiki-GH-017E-en-Spectra-wIRA-sun-halogen-radiators.png
By Helmut Piazena (Helmut Piazena) [CC-BY-SA-3.0-de (http://creativecommons.org/licenses/by-sa/3.0/de/deed.en) ], via Wikimedia Commons.

So what do we, as reptile-keepers, do?
We have no alternative but to use some form of basking lamps and heaters, if we choose to keep ectotherms far from their natural habitats, in climates where they cannot survive outdoors. And if we use them carefully, combinations of incandescent lamps, halides, mercury vapour lamps, fluorescent tubes and even ceramic heaters have proven their worth over decades of successful reptile-keeping. But now we are becoming aware of the inevitable risks that our artificial heat and light sources carry with them.... I don't think there is cause for alarm, or drastic measures. But I'm sure there are things we can do to reduce the risks of too-intense localised heating - which is what seems to be the main issue here.

First, look at Testudoresearch's work with thermal imaging cameras.
Here's the forum post summarising it: http://www.tortoiseforum.org/thread-83263-post-787129.html#pid787129
Any tortoise with cold head and legs (blue in the first picture) is going to hang around longer under a heat source until his whole body is warm. If the heat source is a small circle - a "basking spot" - close under a small halogen lamp (as sold by SO many reptile stores as a "basking lamp") then only the top of the carapace is being heated, possibly quite severely overheated and dried out at the same time, as these images suggest. And how long will he have to stand there, cooking his carapace, to get his core temperature up to the right level...?
So the first very positive step is for every basking "spot" to be converted into a basking "zone", with all sunlight wavelengths (heat, light and UV) covering, as evenly as possible, an area AT LEAST as large as the WHOLE tortoise with his legs and head fully extended. They will happily bask like that, given a big enough zone....
And to obtain this big zone, keepers will almost certainly need to take the second very positive step - moving the lamps further away from the tortoise, and changing all "spot" bulbs to "flood" bulbs. This will spread the beam of heat and light over a wider area. Often, with larger tortoises, it is best to arrange two, three or even more bulbs to cover a large enough area. I've seen this done very effectively in some zoos, using a combination of PAR38 flood halogen or tungsten incandescent bulbs and UV-emitting lamps.
This of course requires the tortoises to be kept in suitably large enclosures or tortoise tables to allow a big basking zone and a big cooler area with a gradient between, and hides/ shelters. In my experience, it is extremely difficult if not impossible to achieve anything satisfactory in anything smaller than 4ft long....

Well... I guess that's my "take" on infrared lighting, to date.... I know I have a lot more to learn, and I'm sure others will chip in with their experiences and practical suggestions...? I am trialling the use of rectangular, outdoor floodlamps which have long thin so-called "linear halogen" R7s bulbs; in the UK these are widely used to light backyards and the sides of houses. They create much wider basking zones than "round" light bulbs. But they seem almost unknown in the States and in other European countries... PAR38 floods seem the next best thing.
And metal halides may be very well worth researching. They have far less IR-B and IR-C than incandescent bulbs and halogens... and a lot better quality visible light, too.

Frances Baines
www.uvguide.co.uk
 

Yellow Turtle

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This is a great article. Thank you for taking the time to share this here.
 

Team Gomberg

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I enjoyed reading this. Learning about IR-A is new to me.
I am so glad to live in sunny SoCal where my torts can be outside either full time or close to it.
Only the leopard hatchlings are raised indoors and the high humidity must be helping to counter act the drying effect of the basking spot.
There is still so much to learn and understand.
 

Testudoresearch

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lilacdragon said:
The infrared wavelengths of sunlight are almost all in the shorter wavelengths called IR-A. There is a small amount of IR-B but no IR-C.
IR-A wavelengths are very close to red light, and indeed they work very much like red light; they can go through the skin and penetrate deep into the body. Think how, if you shine a bright torch against the back of your hand in a dark room, you can see the red light coming through your palm. IR-A will gently warm through the entire body of a small reptile as it basks. Bigger ones will of course take a lot longer to warm up.

Here's a real-life example. From today, 22 December. It has been very warm here, and for the first time since late September, I saw two tortoises emerge to bask.

Ambient temperature at 11.00 am 15.9C, RH 41.8%

activity_22dec.jpg


Subsurface temperature at 50mm (2 inches). 8.00 C

activity_22dec-2.jpg


Ambient temperature and RH at ground level

activity_22dec-4.jpg


Carapace temperature

activity_22dec-9.jpg


Plastron temperature

activity_22dec-10.jpg


The heat in the body is very, very even. Top to bottom (literally). There are 'hot spots' as seen under most artificial 'basking lamps', and although I did not take a cloacal temperature here - on previous occasions I have, and I would confidently expect it to be +/- 1.5C of the external measurements.

Also note that RH is in the 42% max range.

There has been no rain to prompt this (and others remain down), so I suspect these two just felt it was warm enough to come out enjoy the sun for a few hours! Based on previous data, they are easily able to raise their body (including core) temperatures up to 12C or so above ambient by using various basking strategies.
 

Testudoresearch

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Testudoresearch said:
The heat in the body is very, very even. Top to bottom (literally). There are 'hot spots' as seen under most artificial 'basking lamps', and although I did not take a cloacal temperature here - on previous occasions I have, and I would confidently expect it to be +/- 1.5C of the external measurements.

TYPO Alert! That should of course read "There are NO hot spots".
 

keepergale

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Good stuff here. I have just started using radiant heat panels for my tortoises. My impression is it suits them very well. They seem to bask as if they are outside. Still no substitute for the sun.
Does anyone know what "wave length" these heat panels utilize?
 

nearpass

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keepergale said:
Good stuff here. I have just started using radiant heat panels for my tortoises. My impression is it suits them very well. They seem to bask as if they are outside. Still no substitute for the sun.
Does anyone know what "wave length" these heat panels utilize?

I would be curious what type of panels you use, and how you set them up?
 

Testudoresearch

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I have a 400w panel here that we will be running some IR Thermography tests on soon. Quite a lot of these are manufactured as "process" or "industrial control" heaters and frequently state they are excellent for "moisture removal" - which is not exactly what we are looking for with reptiles! So while the heat distribution may be superior to a concentrated spot source, the spectrum is of major concern (and they don't seem to publish much on what that really is).
 

keepergale

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nearpass said:
keepergale said:
Good stuff here. I have just started using radiant heat panels for my tortoises. My impression is it suits them very well. They seem to bask as if they are outside. Still no substitute for the sun.
Does anyone know what "wave length" these heat panels utilize?

I would be curious what type of panels you use, and how you set them up?
I am using a repurposed "Boaphile" cage with their 1611 Radiant heat panel mounted 12 inches above the floor. Its only a 40 watt unit and produces idea temperatures in my reptile room. The cage holds humidity well with it running 24/7. It heats a broad area of the cage but does not seem quite so intense as the CHE's.
 

Testudoresearch

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The core question is:

What is their effect on water molecules in close proximity? If the wavelengths they emit are in the range that is very well absorbed by those molecules, you will get surface (skin) heating with not-so-great deeper penetration... one consequence of that (if it is the case) is that there is an increased risk of tissue damage (burns), and dehydration. .... so knowing what wavelengths are being emitted is critical to being able to predict their effect on living organisms.

Look closely. This is one of our research images that shows an effect from IR-A at close range. What is happening here? See the straight lines in a kind of 'quilt' pattern? Those are the 'sutures' between the plates. These are very rich in blood vessels... hence... water molecules! You can see here how they are getting hotter than the surrounding tissue....they are disproportionally absorbing IR....

range3.jpg


You do not see anything like as extreme an effect as this under natural sunlight. It is one of those 'unseen' consequences that can happen when using very artificial methods of husbandry. I too have been using (and recommending) heat lamps for years with realizing anything like this was happening..... when I first started looking at basking tortoises and turtles with an infra-red imaging system, I was absolutely shocked at what I was seeing. I checked the literature - surely this must be known? Understood? Explained somewhere? Nope. Nothing. So... this is all a fairly recent set of discoveries. We are learning more all the time. I did not begin to understand initially what was causing this.... until I consulted with Frances, who has made extensive investigations into the UV and IR spectra and their effects on reptiles. Only then did it start to "click".... IR-A... water-filtered sunlight... lamp wavelengths...effects on water molecules...

We have an ultra-high resolution IR imaging system arriving in the New Year, so should be able to get even more data on this phenomenon in the near future. This has incredibly wide significance for reptile keepers generally. Not just tortoises. Iguanas... snakes... everything.
 

ulkal

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Apologies for responding so late,especially because this is in response to a question I posed. I did not see this thread and thought my question just disappeared from the radar. Thank you very much for the extensive and comprehensible answer.
So, IR-A is vital to warm up the tortoise, but not its full range. If I interpreted correctly, the lower end of the spectrum does get filtered out less. Would those be the wavelengths that penetrate deeper? And the longer wavelengths in the IR-A spectrum would not go so deep and therefore dry the carapace and skin? I know, I probably oversimplified it, as you cannot bring it down to shorter-wavelength IR-A gets through, the longer-Wavelength IR-A doesn't.
Would running a humidifier, for example, have any effect on filtering out the IRA or would the filtering effect of ambient humidity be so shortlived that it did not matter (I think Testudoresearch showed the diagram of the decrease in RH when running a MVB)
 

Testudoresearch

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ulkal said:
Would running a humidifier, for example, have any effect on filtering out the IRA or would the filtering effect of ambient humidity be so shortlived that it did not matter (I think Testudoresearch showed the diagram of the decrease in RH when running a MVB)

Unfortunately, the amount of water vapor in air between a lamp and a basking reptile as would be generated by a humidifier is so limited it would have no effect at all. It takes many, many Km of water vapor to filter these wavelengths as they pass through the atmosphere, for example. There are such things as water-filtered IR-A (wIRA) lamps (designed for medical use). These employ a liquid-filled filter, sometimes with external cooling systems. This is an example.

They are unfortunately extremely expensive and not practical for routine reptile use, with very high running costs in addition to the purchase price, which is many thousands each....

It would be great if a simple, practical solution existed at an affordable price, but right now, it seems it does not.
 

mikeh

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What about convection heat. Convection ovens are known to cook meats faster and evenly thru out, convection heat "drives" the heat deep into the core without burning the outside.

I have been using this type of heat since I gave up basking bulbs few months back after reading posts about basking lights and their effects on chameleon forum, same as we are discussing here.

While I don't know yet if I am depriving the animal by not providing IRA created by basking bulb, I will say the animal warms up evenly top/bottom, front and back, basks as it would with basking light and acts normal.

In a closed enclosure I sneaked 100W cable across side and back walls (picture flat coil), and use low voltage fan to drive the heat around the enclosure. (T5HO lights provide some additional heat). This forced air circulation drives the heat into the tortoise and substrate as well. Its a slower process, takes about an hour to raise the temp from 75F to 85F and another half hour to 90F. When I check on tortoise tortoise 2 hours after lights on, it indeed is evenly warm to the touch, so is all the substrate. I alternate days between 85F, 90F, 80F,with some spikes of 93F. At 94F and above the tort always retreats into the hide after spending half hour or so at this temperature. Therefore I don't see the need to go much higher above 91-92F.

This type of heat transfer also happens in nature and seems very efficient, think wind. For example, at ambient temp of 85F at ground level, with the forced air circulation (convection heat) the substrate gets warm in reasonably short time. Without the air circulating the substrate never gets warm and stays cool all day. I will get a temp gun to measure this difference, but it is very noticeable just by using hand.

Question is though, am I depriving the animal of something beneficial by using this type of a heat for it to reach its operating temperatures, that I am not sure of. It still warms up evenly including its core to operating and basking temperatures just by different method.
 

Team Gomberg

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Mikeh, I'm very curious to learn more about what you do.
I'll message you for details so I don't detail this thread...
 

lilacdragon

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Mikeh, are you saying that the air throughout your entire enclosure is reaching 85 - 90F/ 30 - 35C ?
This is very strange - how do you achieve a temperature gradient? What is the air temperature in their hide?
If you are using buried heat cable then it will be heating the walls by conduction, and the hot walls will in turn warm the air by conduction, and also warm objects nearby by radiating long-wavelength IR-C. I agree that this completely removes the problem we're discussing regarding IR-A... but I'm not sure about the "forced air circulation drives the heat into the tortoise" ... this seems very un-natural.
What is the humidity like, and how do you control it? I would have expected a flow of warm air to have a desiccating effect.
I was driving north out of Adelaide in October 2006, and there was an "extreme weather" situation, with air temperatures rising to 35 - 40C and a stiff wind. I've never encountered anything like it - getting out of the car, it felt like someone had aimed a gigantic hairdryer at us. Later we learned that every field of uncut barley across the entire section of South Australia had been dessicated by that wind and the whole vast crop, wind-dried and useless, had to be ploughed back under. We saw not a single wild animal or bird, the entire day.

My main concern with this concept is that although warming the whole environment is a good way of creating a habitat for thermo-conformers - non-basking species - it seems un-natural for basking species. Basking species in the wild don't rely upon ambient (air) temperature to achieve their desired core temperature - they typically absorb radiation, a bit like solar panels, until their core temperature is well in excess of the air temperature. So they can be fully active with proper core temperatures throughout the day, when the air temperature is only in the mid twenties C.

Is it okay for them to have to wait until the whole "heated" part of their enclosure has warmed up, along with their bodies, before they can achieve the correct core temperature?

How bright is your illumination, now you have only the UV lighting? I'd have thought it might be rather gloomy..?
What about some metal halides for bright light with a lot less infrared?

Frances
 

mikeh

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Re: RE: Infrared - sunlight vs. basking lamps

lilacdragon said:
Mikeh, are you saying that the air throughout your entire enclosure is reaching 85 - 90F/ 30 - 35C ?
This is very strange - how do you achieve a temperature gradient? What is the air temperature in their hide?
If you are using buried heat cable then it will be heating the walls by conduction, and the hot walls will in turn warm the air by conduction, and also warm objects nearby by radiating long-wavelength IR-C. I agree that this completely removes the problem we're discussing regarding IR-A... but I'm not sure about the "forced air circulation drives the heat into the tortoise" ... this seems very un-natural.
What is the humidity like, and how do you control it? I would have expected a flow of warm air to have a desiccating effect.
I was driving north out of Adelaide in October 2006, and there was an "extreme weather" situation, with air temperatures rising to 35 - 40C and a stiff wind. I've never encountered anything like it - getting out of the car, it felt like someone had aimed a gigantic hairdryer at us. Later we learned that every field of uncut barley across the entire section of South Australia had been dessicated by that wind and the whole vast crop, wind-dried and useless, had to be ploughed back under. We saw not a single wild animal or bird, the entire day.

My main concern with this concept is that although warming the whole environment is a good way of creating a habitat for thermo-conformers - non-basking species - it seems un-natural for basking species. Basking species in the wild don't rely upon ambient (air) temperature to achieve their desired core temperature - they typically absorb radiation, a bit like solar panels, until their core temperature is well in excess of the air temperature. So they can be fully active with proper core temperatures throughout the day, when the air temperature is only in the mid twenties C.

Is it okay for them to have to wait until the whole "heated" part of their enclosure has warmed up, along with their bodies, before they can achieve the correct core temperature?

How bright is your illumination, now you have only the UV lighting? I'd have thought it might be rather gloomy..?
What about some metal halides for bright light with a lot less infrared?

Frances

These are the same questions I ask my self. Yes, this concept seems unnatural given how arid species achieve their operating temperature in nature. But isn't the final effect the same if the tortoise reaches the same operating temperatures?...I wonder.

As for having to wait, to reach operating temperature? I have observed, at least the tortoise here,(New Jersey) in the summer housed outside ( now 8month old GPP) to be active in the early mornings, hours before the sun is up for basking, to be grazing and walking around even in 70F. Basking would occur after during morning hours, avoiding sun during midday hours and basking and grazing again late afternoon. This to me seems tortoise doesn't necessarily need basking to warm up first thing upon awakening to function. I could be wrong.

The heat cables in the closed chamber are not burried. They run across 2 side walls of the enclosure well above tortoise level. The fan runs diagonally next to the cables driving the heat from the cables and gently circulating the air, by no means stiff wind conditions, rather gentle breeze. The substrate is kept moist, misted in the evening, yielding night time humidity in the 90s, but daytime humidity in the 70-80%. Keeping humidity levels up is no issue at all. (After reading Andy's posts I am further reducing the humidity levels, especially day time). There are number of weeds growing inside the enclosure, doing well untill eaten. There is a dense vegetation in one corner surrounding the hide made of rocks, here the air movement is largely reduced. Temperature inside the hide is only 3-4F lower but with no air movement the effect is amplified.

Lighting is done by double 48" T5HO specular aluminum reflector fixture with Arcadia 3D+ 12% tube and 3500k grow tube at 15-17" height. Very bright. This double fixture produces some radiant heat reaching the floor, the tortoise seems to recognize this. (A QUAD fixture could possibly be enough of single source for heat and UVB for smaller tortoises, as the heat ouptut by quad/4 bulb fixture is multiplied. I have inquired Andy about this for his upcoming tests for IRA spectrum, your input would be much appreciated, I have read your articles on Arcadia.)

I use digital readers for temp and humidity but will get a temp gun to take readings of tortoise itself. I base much of what I do with this idea on tortoises behavior. I have seen some distress with this set up at prolonged 94F where tortoise will retreat into the hide. But I have also seen this with heat bulbs. The tort would sit under the bulb until it would reach its upper tolerating temp limit then retreat into the hide, only to repeat this cycle of thermo regulating between hot and cool. At temps of 80-90F tortoise acts normal, active, alert, feeding amd basking.
How about keeping the tort in the range of a sweet spot it is looking for in the first place. Lets say 5degree radiant. Is it necessary to create 100F-105F basking spot with 80F cool end? Perhaps yes if the basking bulb is also the only source of bringing up the ambient temp in the rest of the enclosure. Other wise won't a lower gradient aimed at the sweet spot serve equally without creating this very hot dry spot?

You have valid concerns Frances, and I am not sure if this kind of a set up with convection heat is ok for arid species. I will do some tweaking and take measurements with heat gun.
Mike
 

Testudoresearch

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Interesting concept. While it undoubtedly removes one problem, I also have concerns it may be creating others. I have only done very limited testing with forced-air systems (back in 2009 when looking at vivaria and systems in stores and zoo exhibits), and have never looked at them in sufficient depth, but, unless very careful attention is paid to humidity control, there can indeed be quite serious "dehydrating" effects. If you do use humidification, at a level to overcome that, you enter another danger zone (familiar to HVAC engineers), of creating an environment where fungal organisms and diseases such as legionnaire's disease can thrive. With reptiles, there is the added dimension of removing key thermoregulation 'cues' and opportunities. Tortoises specifically are highly geared to using 'directional' heat from radiant sources, and balancing this with indirect, reflected sources from the ground, etc. They, like many lizards, have highly developed behavior patterns and basking postures designed to 'work' in this mode. If this is removed - you may get the body temperature to where you want it, but what else might be disrupted in the process? One thing I have learned over the years is that the further you remove things from how they are "supposed" to work, the more "invisible" problems you can end up creating.They can stay "invisible" for quite some time. Until things start to crash.

Do not wish to put a damper on people thinking of inventive solutions. We need some solutions. But be careful.

You are quite right that tortoises can, in some circumstances, be active without direct solar heat. Examples include true nocturnal activity in Testudo graeca and Geochelone sulcta... feeding by moonlight... not common, but it certainly happens. We have recorded it numerous times now in Testudo, and the late M. R. K. Lambert recorded it in Mali with G. sulcata.
 
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