Shadow/shade and uvb light

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Mjdeisher

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Possibly a silly question with an easy answer... When a tortoise is in the shade or in the shadow of something, is he still receiving UVA and UVB lighting? He may not be in the direct sunlight but there should still be some lighting coming in, right? That makes sense in my mind at least. Lol.
 

Mjdeisher

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wellington said:
Yes it does make sense and that is right. They will still get the UVB.

Good! When Paul is outside and he kept going to the shade or in the shadow of something, I just kept thinking in the back of my head "eugh, he's not getting enough UVB!" he's been outside almost all day and he is lovin it! I haven't seen him so active!

Aaannnndddd, as we speak he learned how to climb the edge of his balcony pen...
The pic was seconds before he face planted the whole inch and a half fall the the ground. Time to tortoise proof it!

image-2112336750.png
 

Madkins007

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The thing is- they get about 10% of the available UVB as long as there is still enough light see. The other thing is that they get all the UV they need for the day in only a couple minutes and they can store it up. The general consensus is that they only need about an hour (probably significantly less) for a week, and a few months worth may well stock them up for several months- but as far as I know there is no clinical evidence for that last bit.
 

Mjdeisher

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Madkins007 said:
The thing is- they get about 10% of the available UVB as long as there is still enough light see. The other thing is that they get all the UV they need for the day in only a couple minutes and they can store it up. The general consensus is that they only need about an hour (probably significantly less) for a week, and a few months worth may well stock them up for several months- but as far as I know there is no clinical evidence for that last bit.

I've heard anywhere from what you've said to 5-7 hours a week. I just don't like taking chances with the little guy.
 

LestatHIM

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Mjdeisher said:
Possibly a silly question with an easy answer... When a tortoise is in the shade or in the shadow of something, is he still receiving UVA and UVB lighting? He may not be in the direct sunlight but there should still be some lighting coming in, right? That makes sense in my mind at least. Lol.

The answer to this question is actually no. The molecules being hit directly by the suns wave lengths are absorbing 99.9% of the solar radiation if not higher. The molecules absorbing this heat become more excited and produce heat. Light can bounce off of surfaces but the radiation doesn't go with it. If this were the case every time you went outside at night you'd get a "moon tan" from the suns rays bouncing off the moon.

An easy way to check if solar radiation is present, specifically the UVB wavelength, grab a SolarMeter. You will be able to measure the UVB at any given spot at any time.
 

Madkins007

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LestatHIM said:
Mjdeisher said:
Possibly a silly question with an easy answer... When a tortoise is in the shade or in the shadow of something, is he still receiving UVA and UVB lighting? He may not be in the direct sunlight but there should still be some lighting coming in, right? That makes sense in my mind at least. Lol.

The answer to this question is actually no. The molecules being hit directly by the suns wave lengths are absorbing 99.9% of the solar radiation if not higher. The molecules absorbing this heat become more excited and produce heat. Light can bounce off of surfaces but the radiation doesn't go with it. If this were the case every time you went outside at night you'd get a "moon tan" from the suns rays bouncing off the moon.

An easy way to check if solar radiation is present, specifically the UVB wavelength, grab a SolarMeter. You will be able to measure the UVB at any given spot at any time.

The '10% under vegetation' figure comes from investigators using UV meters.

I know you were trying to keep things simple, but light IS radiation- just the part that is visible to the human eye. What radiation does when it hits any surface- skin, leaves, moon- varies by the actual surface and the wave length.

Sunlight, which contains all sorts of radiation besides visible light, can hit a leaf's surface, and different wavelengths do different things. The wavelength of green light is absorbed. The other visible colors bounce off, but the waves above and below them may stick, bounce at odd angles, penetrate, or some combination of the above. UVB treats some things we think of as transparent as opaque (like glass or Plexiglass), but penetrates other things as if they were clear (like some dyed plastics and fabrics.)

The reason we don't get moon tans is because the light bouncing off the moon is scattered through space so only a small percentage hits us, and the part that does passes through miles of atmosphere that absorbs lots of the energy.
 

LestatHIM

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Madkins007 said:
LestatHIM said:
Mjdeisher said:
Possibly a silly question with an easy answer... When a tortoise is in the shade or in the shadow of something, is he still receiving UVA and UVB lighting? He may not be in the direct sunlight but there should still be some lighting coming in, right? That makes sense in my mind at least. Lol.

The answer to this question is actually no. The molecules being hit directly by the suns wave lengths are absorbing 99.9% of the solar radiation if not higher. The molecules absorbing this heat become more excited and produce heat. Light can bounce off of surfaces but the radiation doesn't go with it. If this were the case every time you went outside at night you'd get a "moon tan" from the suns rays bouncing off the moon.

An easy way to check if solar radiation is present, specifically the UVB wavelength, grab a SolarMeter. You will be able to measure the UVB at any given spot at any time.

The '10% under vegetation' figure comes from investigators using UV meters.

I know you were trying to keep things simple, but light IS radiation- just the part that is visible to the human eye. What radiation does when it hits any surface- skin, leaves, moon- varies by the actual surface and the wave length.

Sunlight, which contains all sorts of radiation besides visible light, can hit a leaf's surface, and different wavelengths do different things. The wavelength of green light is absorbed. The other visible colors bounce off, but the waves above and below them may stick, bounce at odd angles, penetrate, or some combination of the above. UVB treats some things we think of as transparent as opaque (like glass or Plexiglass), but penetrates other things as if they were clear (like some dyed plastics and fabrics.)

The reason we don't get moon tans is because the light bouncing off the moon is scattered through space so only a small percentage hits us, and the part that does passes through miles of atmosphere that absorbs lots of the energy.

Clearly I know that light is radiation. And clearly I know that light reacts differently to different surfaces. Wavelengths vary in sizes, UV included. Some wavelengths penetrate as you said because they are smaller than the sub atomic particles that make up atoms and molecules. Obviously this varies depending on the wavelength and molecular composition.

The question was do you get UV spectrum exposure from sitting in the shade or does a tortoise. I said that the exposure would be to the milli percentage if at any. This is clearly obvious because if it wasn't, everyone in their house would have an adequate sun tan simply because the house is externally lite (there are various variables in here as well, specifically with what windows consists of molecularly as well as their thickness). The moon example have some variables to it as well, however that wasn't the point of saying it.

We have to understand also the parameters in which the question was asked. I'm assuming the author was trying to figure out whether the shade would be adequate or atleast semi-adequate for a reptile to harness UV and produce Vitamin D3. The answer to this is clearly no.
 

Madkins007

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Solar meters show that the UVB levels in shade are about 10% of direct light in the area, and we know that species such as the red-footed spends over 70% of their time under heavy vegetation (Moscovits 1985), so unless there is some other mechanism in place, they are getting enough UVB under those conditions. Human skin can produce up to 1000IUs of vitamin D a MINUTE when exposed to UVB, and we need about 500-1000 a DAY. While the same info is unavailable for reptiles, it seems likely that it is about the same ratio.

The reason you don't get a tan in the house is simply because glass and most plastic windows are almost opaque to UVB radiation, and you do not get a good one in the shade because it is not enough energy in a short enough amount of time to trigger the reaction.

I'm not a doctor, scientist or anything, so I can easily be really, really wrong and have been before, but I think I am on reasonably solid ground here.
 

LestatHIM

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Madkins007 said:
Solar meters show that the UVB levels in shade are about 10% of direct light in the area, and we know that species such as the red-footed spends over 70% of their time under heavy vegetation (Moscovits 1985), so unless there is some other mechanism in place, they are getting enough UVB under those conditions. Human skin can produce up to 1000IUs of vitamin D a MINUTE when exposed to UVB, and we need about 500-1000 a DAY. While the same info is unavailable for reptiles, it seems likely that it is about the same ratio.

The reason you don't get a tan in the house is simply because glass and most plastic windows are almost opaque to UVB radiation, and you do not get a good one in the shade because it is not enough energy in a short enough amount of time to trigger the reaction.

I'm not a doctor, scientist or anything, so I can easily be really, really wrong and have been before, but I think I am on reasonably solid ground here.

I'm not sure what solar meters you are using but I have never gotten readings like that with mine... In regards to a red foot, even if they spent 70% of the time under vegetation that's only 16.8 hours. The other 7.2 would be more than adequate to make up for it. In regards to your statements about humans, that is completely relative statement. Not only is it skin color depends, but time of the year dependent, longitude dependent, and age dependent. If it was say July 1st in he northern hemisphere and one had white skin, was young, and lived in the south that statement would be true. Any variation to that statement would change the results immensely.

Actually more radiation penetrates through a window than does in the shade. Depending on the thickness of the material that is as well as direct sunlight. 5/16 inch glass decreases the amount of radiation on my meters by 96 percent and that's in direct sunlight. Sitting in the shade my meters get absolutely nothing, and that's pointing the meters in all directions. If the radiation in the shade is generating enough uvb for one to successfully produce vitamin d, it would also be generating enough to burn them.
 

LestatHIM

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Ill tell you what I'll do. I'm not doing anything tomorrow and it's supposed to be quite hot where I live and have low humidity. I'll take my solar meter out and take readings from various places then post a photo and description of where I got the reading. I'll do it between 2 and 5 so I can be sure I'm getting the highest amount of solar radiation possible.
 

Cowboy_Ken

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But back to the statement of tortoises storing D3. Has this been proven? I recall an abstract conducted with Komodo dragons where in a controlled environment it was shown they can store D3 for up to 6 months. This was converted D2-D3 not absorbed D3 from food sources. I ask because I've often thought the reason Russian tortoises don't pyramid as easily as other tortoises is due to the fact they spend so much time in burrows in brumation in winter and estivation in summer heat. Shoot, I've been trying to get someone to do a thesis on this for the last 5 years!
 
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