UVA and the recommended amounts

[ISTortoiseLover]

I know how important UVB is for tortoises. Most experiments and emphasis are based on UVB from the sun or from bulbs and the amounts emitted. But what about UVA?

I've been looking around but there's not much written stuff about the recommended amounts for UVA. Apart from it being a necessity for general wellbeing/behavioural patterns. And for example, some incandescent bulbs are specially made to produce UVA for basking. Its stated that they produce the optimal amounts of UVA which is beneficial to the torts. Can a normal incandescent bulb do the same, as i'm hearing that they're the same thing.. all the talk about spectrums and stuff and how the torts can see colour only if UVA is present..

In that sense, a UVA bulb's "Lifespan" would also decrease/decay as time goes by right? Should it be replaced annually? I'm always hearing that on average, an MVB bulb needs to be replaced annually.

 

[Balboa]

Good questions, and the answer is , we largely don't know.

My personal take on it is to try to emulate natural sunlight like they'd experience in the wild. I've not found much acceptance for this suggestion however.

"Typical" sunlight has about 1/10 of its make up in the UVA range on a clear sunny day. UVA is more prominent at the equator, and as you move further away becomes less so (as the UV content is diminished by longer travel time through the atmosphere)

An incandescent doesn't normally produce much in the way of UVA. They are tilted more towards the infrared in output. Fluorescents, Mercury Vapors and Metal Halides do tend to produce some UVA, how much of course depends on design of the lamp and enclosure.

As best as I can tell a typical fluorescent produces a close enough ratio of UVA to Visible Light to satisfy the needs of reptiles, so that is what I use. A single UVB fluorescent combined with a couple standard fluorescents probably more closely resembles equatorial ratios. UVB fluorescents alone produce too much UVA to approximate natural sunlight.

Hope this helps.

 

[Madkins007]

Another issue is what does UVA do for the animal? Again, we don't KNOW, but several things have been observed...

1. This may be the most important- UVA affects the brain, and things like the pineal gland. It seems to have a huge role in growth regulation, seasonal metabolic differences, daily rhythms, reproductive cycles, and more. Whenever you see a study mention the benefits of UVA to the 'deep brain', they are talking about the parts of the brain we share with reptiles, so it probably helps them as well.

2. Tortoises can apparently see in the UVA range as normally as we see into the purple range. Cutting out UVA would be like turning all purple colors to black for us- it would make blues and reds look funny, it would make a lot of food look less appetizing, it would even make potential mates look odd if they used red, blue, or purple in clothing or makeup. Even skin tones would be 'off' a bit. UVA seems to play a role in food choices and other aspects of life for tortoises, and probably affects mating too.

3. There is also a chance that without decent early exposure to UVA, the eye may not develop correctly, or that color perception will be permanently affected.

4. They probably use UVA to help guide them to UVB-rich basking spots. In nature, you would not have one or the other- they would always occur together. There would be warm IR as well.

It is probably pretty much a 'some is better than nothing' deal.

 

[ISTortoiseLover]

Thanks for sharing guys. Very useful info there.

Are compact fluorescent bulbs for home use namely, "Philips", safe for tortoises? I know for sure that they are super bright and very uncomfortable if looked at directly. I've seen some of their energy saving compact fluorescent bulbs that produce 6500K (don't quite know what that means) Cool daylight.

 

[Madkins007]

6500K is the 'color temperature'. The higher the number, the more sun-like the bulb is as far as the spectrum it produces goes, to massively oversimplify a really technical topic. 6500K is considered roughly 'overcast noon daylight', but it takes temps in the 8000K or higher range to hit UV.

Check this link and see if it makes any sense to you: http://en.wikipedia.org/wiki/Color_temperature

BRIGHTNESS is measured in watts and is very different.

A plain coiled fluorescent bulb is fine for general light. If you are concerned about the brightness in the focal point, just aim the bright spot someplace tortoises cannot see it and let the sides of the bulb light the space.

 

[ISTortoiseLover]

AH! I see now, most curious. Thanks Mark!
In the end, I bought the Zoomed 100w Daylight blue bulb. heh
I may actually buy a compact fluorescent bulb just for kicks!