Tuesday, April 28, 2009
"Excerpts from Experts Section" (click on July folder)
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Thursday, July 31, 2008
10. I am not familiar at all with Metal Halides. Can you elaborate more about this type of lamp. Do you perhaps have a Metal Halide Spectograph that you can share with us? -Q contributed by Kevin Zamp-
Metal halide lamps are basically mercury vapor lamps with added compounds of various metals and halogens inside the arc tube. There's a great description of these here: http://en.wikipedia.org/wiki/
The exact combination determines the color of the light produced, and it is much brighter than an ordinary mercury vapor lamp. A good quality 70W flood will produce maybe 75,000 lux at 12 inches... that's illuminance at full sunlight levels. Obviously you don't need to have the lamp so close... placed at a greater distance, the light will cover a much wider area but still provide intensely bright illumination.
The other impressive thing about metal halides is that ones with "daylight" color balance (around 5,000 - 6500K) have so many "spikes" of light at different wavelengths, produced by all the different chemicals, that the spectrum is almost continuous. This makes for extremely good color rendering - the spectrum is more like sunlight than any other lamp.
This chart shows the spectra of sunlight, one of the best metal halides, the Iwasaki/Eye Lighting Color Arc PAR36 (sold for human use) and a mercury vapor lamp for comparison.
They are all externally ballasted, because they need really precise control of their operation. And just any old ballast won't do. The quality and color of the light is extremely sensitive to the current flowing through the arc tube. High quality ballasts are needed to avoid flicker, frequent cutting-out and re-starting, and loss of the full color spectrum.
They are ignited by a 4KV initial pulse from this ballast. This requires excellent electrical connections and fixtures designed to handle that sort of voltage, as well as the heat. Anything less - moisture or dirt in the terminals, for example, or too long a cable between ballast and lamp - and the lamp may fizz and sputter, but it won't ignite properly. (They take a few minutes to ignite and reach full brightness anyway, often with assorted flashes and flickering).
The Solarmeter 6.2 is the most versatile and useful broadband meter available; I wouldn't be without one. But like all broadband meters, it can only measure what it "sees"; and it sees the whole spectrum from UVC to a short distance into the UVA. This means it can't distinguish between a lamp that produces a lot of dangerous very short wavelength UVB from one which produces a lot of harmless long wavelength UVB. In other words, you can use it to monitor a lamp's decay, but you can't use it to decide how similar a lamp's output is to sunlight, or to compare one brand of lamp with another.
The 6.5 meter gives the readout in terms of the easily understood UV Index. If we know the basking habits of our reptiles, we can estimate the UV Index they would choose to expose themselves to, in the wild, and then decide how much UVB to offer. It's a very handy safety feature, too. The highest UV Index ever seen, at mid-day on the equator at sea level, is around 16 - 17. Reptiles would rarely venture out into that. So what would you do if you discovered your new lamp would expose your reptile to UV Index 100 or more? Sadly, this is no joke...I know some "spot" mercury vapor lamps still on sale today which emit extremely dangerous levels like that, at the manufacturer's recommended basking distances..
The only drawback with the 6.5 meter is that it's measuring such tiny amounts of light that the UVB from a fairly low-UVB fluorescent tube, at basking distances, will hardly register a flickering 0.1 or 0.2 on the meter. At the very limits of its resolution, the meter is not very accurate at such low levels.
But unfortunately, the 6.5 meter not be on every herper's shopping list, today.
It relies upon a SiC sensor. These are now considered outdated, and are being replaced by AlGaN sensors in most applications. The supply is now very limited; they are no longer being manufactured, and only one supplier, with dwindling stocks, now exists. The Solarmeter 6.5 with a SiC sensor has just unavoidably suffered a massive price increase as a result, although Steve Mackin believes he will be able to supply these very special meters for some time to come.
The AlGaN sensor is suitable for monitoring sunlight and lamps with spectra very much like sunlight. However, it does not respond well to short wavelength UVB and UVC, and as a result broadband meters fitted with AlGaN sensors do not give comparable results with many types of reptile lamp, and in fact the ones I trialled were unable to detect hazardous output from several lamps giving extremely high UV Index readings with the original Solarmeter 6.5 with the SiC sensor.
12. Let's say that we allowed sunlight into our reptile room. Even though it passes glass, does it still keep a lot of the spectrum below the UVB level? -Q contributed by Kevin Zamp-
No. Ordinary glass (as opposed to quartz glass) acts like a UV filter, progressively blocking shorter wavelengths of UV. Window glass blocks 99 - 100% of the UVB. It allows some UVA through (about 65% at 350nm) and almost all visible light (over 90%).
If you want to glaze a window to let in some UVB, though, special high-transmission glass (which is very low in iron) is available which will let some UVB through. In the USA, one such glass is PPG Industries "Starphire" Uncoated Ultra-Clear Float Glass. Two brands which can be purchased in the UK are Asahi Glass Company's Planibel Clearvision (28% transmission of UVB at 305nm) and Pilkingtons' OptiWhite (25% transmission at 305nm).
13. What do you think of external vs. internal ballasted lamps for MV and MH (if it comes that way) -Q contributed by Kevin Zamp-?
From the point of view of light quality, one might think self-ballasted (SB) mercury vapours would be better than externally-ballasted (EB) ones, because of the tungsten filament producing some continuous-spectrum, golden light to offset the very "spikey" spectrum and very poor colour rendering of the light from the mercury arc. They are marginally better; but the arc tube is so bright it overpowers the tungsten filament. In my opinion both SB and EB lamps should be combined with "daylight" full-spectrum lighting, ideally with a continuous spectrum, as I mentioned before.
The main reason for choosing an SB lamp would be to increase the heat at the basking spot. A 160W SB MegaRay produces a very suitable basking spot for my chuckwallas (up to 120F!) which is quite impossible with a 60W EB MegaRay. Conversely, an EB lamp would be much more suitable for use with montane species, requiring high UVB but lower temperatures.
14. So, as regards provision of the best light for reptile keepers, do you have any more tips that you can share?
If anyone asked me to summarize everything in just a few sentences, I'd probably say:
Research your species! Plan to mimic its natural light environment as far as possible.
"Select and combine" lamps to get the best spectrum you can.
Always, always check your temperatures.
Never buy anything just because it's really cheap. UVB lamps are health products, like drugs, not fashion accessories like plastic plants or food bowls. Would you buy a packet of pills if you didn't know what was in them?
15. Last, but not least, what is next for you? Any exciting researches you are going to do? Books to publish?
Right now, I just want time to update the UV Guide UK website!..... but one day, yes, I do hope to write a book on the subject. There is a lot going on at the moment, too, that I'm very excited to be involved with. For example, Peter Nunn at Alice Springs Desert Park has completed a marvellous survey of the voluntary UVB exposure of wild long-nosed dragons over a full year; we hope to write up this study with Dr. Gary Ferguson.
Thank you so much for this wonderful opportunity! I wish you many success for your future research.
----- End of the Interview ------
7. The key of providing the best lighting for our reptiles I believe relies on our knowledge in how a specific reptile receives sun light in his microhabitat. With that said, having a UV light directly on shine 12 hours a day and the 6" usual distance, is that even close to ideals?
What can we do, as hobbyist, to be able to correctly measure the proper "light" for our reptiles?
There are a few studies being done right now for a tiny handful of species, but the "unknowns" far outweigh the "known".
Common sense, though, is a powerful ally; as is the knowledge that the reptile himself is extremely aware of his needs and has evolved to seek out the optimal environment from what's made available to him. If he's got the space to move around and plenty of choice between areas of full light, dappled light, and shade, at different times he will choose different parts of the enclosure, as he would select different parts of his territory in the wild.
Here are my suggestions:
1. Research your reptile! Don't even buy a "beginners" reptile like a leopard gecko until you know where they live in the wild, how they behave in the wild, and whether you can re-create something vaguely resembling that landscape, with its places of shelter (trees, branches and leaves? Rocks and caves? Underground tunnels?) And its combination of light and shade, hot and cold, wet and dry.
2. Buy the best equipment you can possibly afford. The cheapest is hardly ever the best when it comes to heating, lighting and measuring devices. I believe proper digital and/or non-contact thermometers, dimming thermostats for heat lamps and quality UV lamps are essential, not optional extras. A UVB meter is very expensive but saves a lot of anxiety; metabolic bone disorder is one of the most common health problems in captive reptiles, but as far as I know, it's unheard of, in the wild.
3. If you know that your species naturally basks in sunlight, make your vivarium large enough to create a small patch of "sunlight" inside.
Sunlight contains UVB, UVA, good visible light and infra-red (heat). You will need more than one type of lamp to supply all this in one zone. You are trying to create a "sunlight gradient" here, with the UV, visible light and heat diminishing steadily with distance from the source; but the "basking zone" needs to be large enough for the whole body of the reptile to fit inside it. Think carefully about its location and provide nearby shelter. Double-check your temperatures both in the basking zone and at the cool end. Overheating is all too easy when creating "sunlight" indoors, mainly because of limited airflow.
4. Visible light levels are very difficult to guess at, because our eyes accommodate so well. Reptile eyes also accommodate; but the light that reaches the reptile brain directly through the skull is important as well. We can't re-create the full brilliance of natural daylight indoor, let alone sunlight. But if your species basks in sunlight, then the basking zone must surely provide intense full-spectrum, white "daylight" - incandescent lamps or metal halides to provide thousands of lux, not just a few hundred lux from a fluorescent lamp, and certainly not a red "infra-red heat lamp"!
Then, open areas in the rest of the vivarium need to be well lit, too. You don't want a "spotlight on a darkened stage" effect; your reptile needs to be able to see everywhere, not just inside the basking zone. This is where good fluorescent "daylight" tubes can be useful, if you don't want any more heat. For lighting really large habitats or whole rooms, wall or ceiling-mounted metal halides high above the enclosures are unbeatable.
4. The sun is overhead during the day; eyes are designed to cope with this. Avoid angling lamps sideways straight into an animal's line of sight. Do you like driving your car straight into the setting sun?
I'm sure you can think of many other useful and sensible ways of improving a reptile habitat. Examples include altering day length with the seasons, if appropriate; simulating dawn and dusk, by timing the lamps with a lower color temperature (more golden, less UV) to come on earlier, and to switch off later, than the blue-white UVB lamps. If you have a much more sophisticated set-up, you can simulate sunrise and sunset even more accurately with dimmers and so forth.
With that said, we keep reptiles successfully, in my opinion, only because these amazing creatures are remarkably well adapted to survive in adversity.
8. Talking about microhabitat, I know that your research (please correct me if I am wrong) deals with measuring UV rays in reptiles’ microhabitat. Is there a specific research that deals with chameleon in their microhabitat that you know of?
There would have been, but it never happened.
Last February, Dr. Gary Ferguson and Bill Love, specifically to record the UVB, visible light and temperature of chameleons in their native habitat, planned a most exciting little research expedition to Madagascar. Unfortunately, not enough participants booked to go on the trip, which was being organized by Bill as one of his "Blue Chameleon Ventures" Madagascan tours. So it didn't go. Perhaps, in the future...
9. So, now that we understand a bit about attributes of light and reptile needs of light, we finally come to our husbandry. So far, do you have any leaning toward certain type of lights? (I know you mentioned about metal halides).
Sunlight is the perfect light source.
I think the seasonal changes in my own reptiles' behaviors are initiated as much by the changes in daylight they see through the windows as by my feeble attempts to change the day length using timers on my lamps. The night drop in temperature also increases in winter, I think this too plays a part, but I lean towards letting them see daylight as much as possible. My friends Andy and Jeanette Beveridge are very experienced with chameleons and put them in outdoor cages (with appropriate shelter) when the weather is right. My bearded dragons enjoy as much outdoor sunlight as they can get.
Indoors, I think Dr. Henry Brames' catchphrase "select and combine" sums up my view very well.
I would always want to combine a bright lamp with a continuous spectrum (such as a tungsten or halogen incandescent lamp - predominantly light from the red and yellow end of the spectrum, with much less blue and UVA) with a UVB lamp designed for reptiles, which provide UVB, some UVA and a discontinuous spectrum which does however have peaks in blue, purple and UVA.
The sort I would choose would depend on the species and on the vivarium size. My leopard geckos, for example, have small 2ft - 3ft vivaria equipped with household 40W incandescent lamps on dimming thermostats and UVB fluorescent tubes with good UVB spectra but relatively low output (such as ZooMed Reptisun 5.0, Arcadia D3 Reptile, Sylvania Reptistar). My bearded dragons have larger vivaria (4ft+) and these utilise 80W PAR38 incandescent flood lamps combined with flood-type mercury vapour lamps with high UVB output (such as ReptileUV MegaRay and T-Rex Active UV Heat Flood)
But recently, I have been testing some of the new metal halides which emit UVB, and yes, I am impressed. At the moment I'm using them in 4ft vivaria with my chuckwallas and my little Ctenosaur palearis, and I think eventually I might use them instead of the mercury vapour lamps, for all the sun-loving species.
To be continued to Part IV--------------
Wednesday, July 30, 2008
5. Your comment of “UVB lamps should be positioned over the basking zone” and “D3 synthesis requires warmth” intrigues me. In your opinion, do reptiles have some perception of the presence of uvb and heat as different entities? Or do they assume visible light means warmth and uvb in one. What is the problem, if there is any, from separating uvb to one end and heat bulb to another end?
Dr. Gary Ferguson and his team have done pioneering studies into the reptile "perception" of UVB, working with Panther chameleons. Their carefully designed experiments do suggest that chameleons, at least, can perceive UVB - or at least, perceive locations where there are higher levels of UVB - since, if they are deficient in vitamin D3, they choose to spend longer in these areas.
Chameleons were given the opportunity to choose whether or not to bask under UVB or UVA lamps in an enclosure where both shady and exposed areas were held at a uniform ambient temperature (about 29C). The chameleons were significantly attracted to the light from both lamps, and the vitamin D3-deficient ones were more attracted to the UVB lamps than the UVA lamps.
This does suggest that they are attracted to light even when it is not associated with heat, and that they can perceive UVB as a separate entity from UVA. What exactly do they perceive, though? They can definitely see UVA, but it seems unlikely, given the properties of the reptile eye, that they can actually see UVB. Maybe they can feel it on their skin; maybe the "feel-good factor" humans experience under UVB, possibly linked to endorphin production, is a faded human version of what a reptile experiences?
But can chameleons perceive light and heat as different entities? We can't really deduce that, because this experiment doesn't investigate the chameleon's perception of heat, at all.
I know of very few studies on reptiles where the components of sunlight have been separated out, to see what choices the reptile will make. Since a reptile must maintain its core temperature between very specific limits for life itself, we might hypothesize that if reptiles can distinguish between them, they would select basking spots based upon the temperature there, rather than upon the presence of light or UV light in the area.
One experiment conducted on spiny-tailed iguanas by Dickinson and Fa (1997) showed that these lizards were all significantly more attracted to an incandescent lamp than to a non-light-emitting heat source or a UV tube, which seems to undermine the theory. Unfortunately, the results are not conclusive, because the temperature under the incandescent lamp was hotter than under the non-light heat source, and much hotter than under the UV tube.
More research is needed! However, part of Dickinson and Fa's study clearly showed that when the choice was between the incandescent lamp and the UV tube, the lizards were primarily attracted to the lamp; they spent comparatively little time under the tube.
If we separate our UVB tubes from our heat lamps, then this is an unnatural state of affairs, which requires the reptile to make a choice it would not need to make in the wild. The captive reptile in this situation cannot absorb UVB and bask at the same time. Even if it "knows" it needs UVB, the vital necessity of maintaining a suitable body temperature seems likely to be prioritized over UV absorption, which could well be much reduced as a result. But someone needs to do the experiments, to find out whether this is indeed the case.
6. So many elements need to be considered in simulating light in captivity to be as close as possible to natural light. What about the effect of moon light to reptiles? Is this something that we might, in the future, be interested to simulate as well even for diurnal reptiles such as chameleons?
Here's what seems to be a popular view: "Reptiles can't see red light, and infra-red lamps aren't very bright, so they can be used 24/7 as a heat source. Alternatively, moonlight is blue, so deep blue lamps can be used to simulate moonlight. Moonlight is natural and won't affect the reptiles. The lamps look really nice to me, and enable night-time viewing."
The only part of this which is true is ". The lamps look really nice to me, and enable night-time viewing." I am convinced that using lamps at night is solely for the benefit of the human owner.
Firstly, reptiles can see red light. It is true that some reptiles lack a "red" cone in their retina; but, so do colorblind humans, and red light isn't invisible to them, either. Red looks bright; it's just not a distinctive color to them. Chameleons do have a "red" cone however, and can see every color in the spectrum, from UVA to red.
Secondly, moonlight is NOT blue. It's sunlight reflected off a huge light gray lump of rock - it has all the colors of sunlight - it's a slightly yellowish white. You can see this on spectra; but you can also prove this easily by taking time exposures with a camera. If you use digital, it's vital you switch the "color balance" to "daylight" to stop the camera correcting for a color cast, because you want to know what color cast, if any, there is.
Here is the photo of the moon, almost due South of me.
The light isn't blue. Notice the white moon and the color of the clouds. There is also a hint of a "halo" from ice crystals - note that the trace of a rainbow in the cloud on the left of the moon has normal colors in it.
Here is a flash photo of the view from our garden (to prove it was very dark at 12:43 am) aimed at the moonlit hillside to the north.
Here is the same view, taken one minute earlier, on a tripod with no flash and a 20-second time exposure at f4.
Moonlight is very dim (about
0.5 - 1 lux). Here is my lux meter, caught with a flash photo whilst reading 1 lux from the moon.
Thirdly, artificial "moonlight" and "infra-red" lamps are, compared to moonlight, intensely bright!
Here are some test result taken at 12 inches below the lamp using a lux meter:
Exo Terra Night Glo 50 W (Dark Blue) and Hobby Moonlight 40 W (Dark Blue) = 89 lux
Hobby Moonlight 75 W (Dark Blue) = 239 lux
ZooMed Nightlight 60 W (Red) = 349 lux
ZooMed InfraRed Heat 100 W (Red) = 4,880 Lux
For humans, darkness enables the brain to synthesize melatonin, important in setting daily and seasonal body rhythms. If we are exposed to bright light in the middle of the night, melatonin synthesis stops dead in its tracks, and, ironically, blue wavelengths are by far the most effective for suppressing synthesis.
I'm not sure that a totally natural "day" and "night" are ever possible for a reptile kept in human habitation. But, I do think "night lights" can only make things far worse for the little guy in the cage.
Frances Baines in Galapagos Island. Photo taken by Janette Beveridge.
Courtesy of Frances Baines.
Mrs. Frances Baines, M.A., Vet.M.B., M.R.C.V.S.
is a veterinarian particularly well known for her astounding dedication in the research field of visible and UV light for reptiles. she works as an advisor to the Reptile and Amphibian Working Group of the British and Irish Association of Zoos and Aquariums. You can visit her website for more detailed information about her works and research at: http://www.uvguide.co.uk/
A bit of my thoughts:
I contacted Mrs. Frances Baines for an interview request in June 2009. To my surprise, I found out that she was well aware of my blog from her acquaintances. A simple interview turned out to be a very informative and enjoyable experience. I thought of editing some of the info to fit this interview in one section. Yet, I changed my mind. I wanted to share as much as information that I got during the interview to all of you. So, this interview will span to 4 sections instead.
I hope you guys will enjoy this.
My questions are in red.
Mrs. Baines' answers are in blue.
Interview Date: July 7, 2009.
1. How did your interest in reptiles begin?
I grew up in Hampshire, England, near one of the last remnants of natural lowland heath, and I was one of those strange young teenagers who spent most of her summers not trying on miniskirts and lipstick, but either knee deep in heather and gorse looking for wildlife, or bringing home lizards, frogs and newts “to populate the garden”, to the horror of my mother, who was terrified of them. Back in the 1960s and early 1970s, no one I knew kept reptiles in captivity. But I loved the little wild ones.
2. Is there any particular reason or history behind your interest in researching about UVB?
Years ago, when our first much-loved bearded dragon, Pog, developed metabolic bone disorder despite the use of a supposedly high-quality UV lamp, I was devastated. I knew little about UV light, and I had relied upon the product advertisements. After researching, I was astonished to discover how little good information on UV lighting was known.
In 2004, I came across a new Internet mailing list being set up by hobbyists in the USA http://pets.groups.yahoo.com/group/UVB_Meter_Owners.
There, I heard about a hand-held UVB meter available in the USA; and I read about a new mercury vapor lamp called a ReptileUV MegaRay, that Bob MacCargar had invented. I asked him about his lamp. To my amazement, he offered to send me a sample.
On the mailing list were two chameleon owners from the UK - Andy Beveridge and Rob Lane. Rob imported the very first Solarmeter 6.2 UVB meters into the UK. And, we began testing UV lamps, along with fellow herp keeper Rachel Hitch.
We launched the website www.uvguide.co.uk on 26th July 2005. Recent involvement with a number of zoos and research groups worldwide has greatly broadened the scope of the project. Contacts include veterinarians, zoo keepers, herpetologists, conservationists, major reptile lighting manufacturers and distributors, and many enthusiastic keepers and hobbyists who are working with us to improve the lives of reptiles in captivity. Over the years, Rob and Rachel have moved on to other things. Andy is our technical expert, and taught me how to use his two new spectrometers; I've taken over almost all the lamp testing now.
We now have a range of meters as well as the spectrometers, and it's not just UVB I'm measuring, but the whole solar spectrum and its artificial equivalents. Reptiles are quite literally "solar powered", and it is exciting to be learning so much about different aspects of their lives.
3. Herp hobbyists always strive to find a perfect light for our pets. For new reptile keepers, what are the components of Sunlight that needed by solar powered reptiles?
In a word: everything! Reptiles are very sensitive to all aspects of sunlight. Sunlight is a radiant energy, extending from the shortest UVB wavelengths that the atmosphere lets through (around 290 - 295nm) up to UVA and visible light, right up to infrared, which we think of as radiant heat. All of these parts of the spectrum are vital to reptiles.
UVB is needed for vitamin D3 synthesis in the skin. It also has direct effects upon the immune system and skin cell division, and may even enable synthesis of endorphins - the "feel-good factor" of sunshine.
Short-wavelength UVA works alongside UVB in preventing overproduction of D3 and also has a protective effect against cell damage from UV light. Both UVA and UVB stimulate long-term changes in the production of melanin and, possibly, other pigments in the chromatophores.
Longer wavelength UVA (from about 350nm) is visible to reptiles - it is a "color" in their rainbow. Iridophores can reflect it; certainly many reptiles have UVA markings as a result. UVA is therefore a necessary component in reptile lighting.
What about visible light? We think we know why this is important to a reptile.... for vision. But that's only half the story. Light penetrates through the body of a reptile - through the skull - and light-sensitive cells in the brain. In those species, which have one, the parietal eye (third eye) responds also to green and blue light. These light-sensitive cells then relay information about the intensity and duration of the light to the parts of the brain which control diurnal and annual circadian rhythms - setting the body clocks for sleeping, waking, activity levels, seasonal behavior.
Another element to consider is infrared. Although it is invisible to us, infrared is readily experienced by all species as radiant heat. It is absolutely vital to all basking reptiles; behavioral studies suggest that they associate it with bright visible light - presumably because in nature, that's what sunlight is! I will also add that the final stage of vitamin D3 synthesis requires warmth, so for basking species, UVB lamps should be positioned over the basking zone.
4. Beside the major components UVB and UVA, your researches made me aware of another components that I often neglect, which are spectra and intensity of light. How important are those two in successful keeping of our reptile pets?
Anecdotal evidence suggests that reptiles are attracted to natural sunlight in preference to artificial light, and many keepers report astonishing changes in activity levels when reptiles are given access to natural daylight. Both the intensity of the light and the quality of the spectrum are probably playing a part. Since every reptile has evolved to thrive best in its natural habitat, I am absolutely convinced that replicating the natural lighting of a species in its microhabitat is a major key to success.
First, lets talk about the spectra.
Sunlight produces a perfect "rainbow" - the spectrum contains vast amounts of light in all wavelengths - all colors. Artificial light sources are very different to natural sunlight.
Incandescent lamps (tungsten and halogen "basking lamps") have continuous spectra (light in all wavelengths, rather like sunlight), but the shortest wavelengths are largely absent. There's no UVB, only small amounts of long-wavelength UVA and not a lot of purple and blue. So they are great for providing yellow, red and infrared, but little else.
Fluorescent tubes and compact lamps rely upon mercury vapor and phosphors to produce light. These don't produce continuous spectra - the easiest way to think of their light is in terms of a small number of "spikes" of light in a few basic colors - purple, blue, green, yellow - which the human eye and brain blends together, so we think we see white. So-called 'Daylight' phosphors produce slightly more continuous spectra with some light in the wavelengths between the "spikes"; other phosphors produce light in the UVA and UVB ranges.
Unfortunately, it's hard to know what a reptile actually sees when it looks at fluorescent tubes. Most reptile eyes have four color cones in the retina, responding to different wavelengths from our three. Does he see the light as white? Or does it have a weird color cast? We do not know.
Mercury vapor lamps (MV) don't usually have phosphors, so the main visible light is solely from the "spikes". If the lamp is self-ballasted, there's also a tungsten filament so there's a little yellow and red from that; but it doesn't improve the color balance of these lamps very much. Even to human eyes, these lamps produce light that never looks quite right.
A fluorescent lamp or MV lamp can be combined with an incandescent lamp, to get the best of both worlds. The tubes or mercury vapor lamps provide the UVB, UVA and most of the blues; the incandescent lamps add yellows and reds. It's not ideal, but it's an improvement over either lamp on its own. Friends of mine who keep chameleons have reported great success with both of these "combos," with the actual lamps chosen to provide appropriate levels of UV, heat and light for the relevant species, of course.
Metal halides may be the best solution to date. They operate on the same principle as the MV lamp, but they produce many "spikes" representing most colors across the entire spectrum. Some "Daylight" versions such as the Iwasaki/ Eye Lighting Color Arc 6500K lamp have spectra that, in the visible range, are very much like the sun. My colleague Andy Beveridge was astonished at the positive way his C. quadricornis responded to light from metal halides.
Unfortunately there are very few of these, which have been designed to emit UVB as well. ReptileUV are developing a UVB-emitting halide in their "MegaRay" range, which looks very promising. In Europe, Lucky Reptile (a German company) has launched a range known as the "Bright Sun UV" series. The spectra of these also look promising. Long-term studies are under way here, with samples from both of these companies.
In the meantime, excellent results should be possible using high quality UVB fluorescent tubes in combination with metal halides. Of course, once again, the intensity of light and of UV from such combination must be appropriate for the species.
Which brings me on to the next point: the intensity.
Our eyes are designed with pupils, to control the amount of light reaching the retina and keep the light level inside the eye within strict limits, to optimize vision. That is why we have no problems living indoors all day with approximate light levels of 1,000 lux, and are not consciously aware that this is little better than outdoor light a few moments after sunrise. And, yet at mid-day, outdoors, bright sunlight may provide 100,000 to 150,000 lux. Reptile eyes can adjust to the light just like ours. So what is the problem, once the light in the vivarium has a reasonably natural spectrum?
This is the point at which I like to speculate, because I know of no direct evidence to support my theory. However, consider this: The light-sensitive cells in the parietal eye and in the brain itself do not have a pupil to shield them. They are designed to register the intensity of natural sunlight.
The lizard evolved to walk out under the sun. if 100,000 lux shines down upon the top of his head, how many lux do you think flood through his skin, through his skull bones or the gaps between them, and reach the parts of his brain that program his activity levels and set his body clocks, stimulate serotonin synthesis, and tell him "hey, it's mid-day and it's mid-summer"?
Now put him in a cage and give him only a fluorescent lamp that emits just 500 lux at 12 inches distance. How many lux reach those light-sensitive cells now?
I am not saying we need to re-create the full brilliance of the mid-day sun indoors, even for the most hardened desert sun-worshipper. But, I do think we need to throw out any notion that reptiles - even crepuscular species - can be kept in gloomy tanks with just a ceramic heater and a dim fluorescent tube. Even nocturnal species may peer from their daytime hiding places at the bright sunlight outside.
Drs. Lynnette Sievert and Victor Hutchison in Oklahoma conducted a research over 20 years ago. They put Tokay geckos in three different situations. In one, there was only diffuse, soft lighting throughout the enclosure during the 12-hour day. In the second, there was a very bright light over the warm end of the tank, and in the third, the bright light was over the cold end - something that wouldn't happen in nature. The geckos, being nocturnal, didn't do a great deal when the lights were on. But they were markedly affected by what they perceived. The "diffuse light" and "bright warm light" groups showed clear differences in their body temperatures during the day and at night - they thermoregulated more accurately, and maintained their body temperature higher at night than they did during the day. But the "bright cold light" group behaved quite differently. Their body temperatures hardly varied between day and night, and they actually thermoregulated less accurately during their nightly activity period.
To be continued to Part II----------------
Monday, July 28, 2008
My question in red
Dr. Ferguson's answer in blue
Interview date: February 29, 2008
1. What start your journey in chameleon studies, Dr Ferguson?
I had become fascinated by old world chameleons from books and pictures as a teenager. However, I never had a chance to see one until I was in graduate school in 1967. A student in a herpetology class I was taking brought in one that he had collected in Spain. My next contact with real chameleons came when the large pet-trade importation from Kenya began in the late 1970’s. Jim Murphy, curator of reptiles at the Dallas Zoo at that time, had purchased several for the zoo and some of the Jackson’s had babies. He donated a pair of babies to me at TCU in 1977 and the rest is history. I started my first scientific study of them in 1980 with a trip to Kenya. After another trip to Kenya in 1983 several of us published in 1988 the description of Chamaeleo jacksonii xantholophus from Mt. Kenya.
2. In your Panther book, you talk about 5-15uW/cm2 of UV-B for 12 hr/day. I've measured the levels at the basking site (Reptisun 5.0) and have kept the UV-B levels near your recommendation for my Panthers and Veiled chameleons for years with no problems. In addition, with good So Cal beach weather, they get to go outside (100-300uW/cm2) on weekends, weather permitting. Many of us are familiar with keepers/breeders who use MV UVB sources with levels 50-100uW/cm2 12hr/day that "appear" to be successful at keeping them for years at those levels and claim some visible benefits. I suspect that the chameleons are doing a decent job at regulating their exposure levels on their own. I'm sticking with your levels but I'm interested in anything you have to add to your previous conclusions!
-Q Dave Weldon-
One of the problems with measuring UVB irradiance is that different brands of meters give different readings from the same light source. The 5-15 recommendation was given at a time when we were using only Spectroline meters. The current spectroline meters (if indeed that are still available) are impractical for herpetoculture use because they read only in 10-microwatt increments, i.e. the resolution is poor for the low irradiances we are interested in. The more important recommendation was to provide a UVB source with maximum level that cause between 0.18 and 1.52 percent conversion of provitamin D to photoproducts in 2 hours in the ampules we have been using. Bill Gehrmann and I have been testing several meters to determine the relationship between readings and provitamin D conversion. The readings from the Solartech 6.2 meter that give the 0.18 to 1.52 percent conversion are about 10-50 microwatts per cm2. If the maximum source is higher and the lizards have an opportunity to photo regulate be moving in and out of the High UVB zones that is fine. That is what they do outdoors. Remember our study involved "involuntary doses" and the animals were on a low vitamin D diet. What they need will vary with diet and could vary between animals and populations.
3. We work hard to improve the CA-Ph ratio of our non-WC feeders. What research data is available on the Ca: Ph of the diet of wild chameleons?
-Q Dave Weldon-
There are no data that I am aware of regarding Ca P dietary intake in the wild. Most people assume that a 1.25-2:1 Ca: P ratio is good in the diet because that is approximately what you get in the blood of healthy animals. However, animals are probably pretty successful at regulating to those levels regardless of the intake ratio, providing the diet contains some of each compound and isn't too deficient in either. Let me hasten to add that I am not a physiologist or nutritionist, so this may not be a good explanation of things!
4. After reading your Thesis "Do Panther Chameleons Bask to Regulate Endogenous Vitamin D3 Production," I learned that chameleon in general produces its own D3 when exposed to Sunlight, what is your recommendation on supplementing vitamin D3 to chameleons in captivity- specifically to those who allows their chameleon to bask under the real sunlight for at least once a week? Is there a way to know how much do they actually need? Do chameleons have some kind of innate sense to avoid UVB when they have enough D3 in their body?
I recommend little to no dusting of insects with vitamin-mineral supplement containing Vitamin D3 unless the animals get no UVB. Even then, there is a risk of giving too much. Many of the commercial cricket feeds contain vitamin D3. I think that is ok to use those feeds regardless of the UVB environment of the chameleon. Crickets probably don’t gut-load enough from those feeds to cause vitamin D-toxicity. Unfortunately, dose-response studies for dietary vitamin D have not been systematically done like our dose-response study for UVB in the 2002 article. So, dietary requirements are mostly guesswork. However, Larry Talent successfully raised panthers to maturity without UVB and measured the dietary levels of vitamin D by injecting it directly into their mouths. I think I gave the recommended doses that he used in my book (oral solutions of Vitamin D3: 25 IU/week). I fully believe the claims of breeders who say they have raised and bred panthers with only dietary D. However, I do think that panther chameleons have a “sense” of their internal vitamin D-condition and can regulate their exposure to UVB accordingly. It makes a lot more sense to me to let the animals decide how to regulate their vitamin D-condition via exposure to UVB than us by guessing at appropriate dietary levels. If the chameleon fails to do this, I think it is because some artificial light sources confuse them. When the UVB source is in one part of the cage and visible light and heat is in another, they may have trouble judging the proper exposure. I have seen a couple of examples of this in large artificially lit zoo enclosures. While chameleons can burn their skin or their eyes with too much UVB or UVC (see Frances Baines website for info), they can’t harm themselves with overproduction of vitamin D. At some point of UVB exposure only inert photoproducts that aren’t toxic are produced in the skin.
5. As far as Chameleon's adaptation, I heard that some reptile species have pigmentation of the coelomic cavity and organs. The theory is that it helps absorb light and heat, or that it may help reflect solar radiation depending on the species. Is that also true for chameleon specifically for veiled and panther?
I have dissected a lot of panther chameleons and they do have some coelomic pigmentation but I can’t recall exactly how much and how it is distributed. Basking lizards in general do have dark pigmentation surrounding either the coelomic cavity or vital organs such as the gonads. Those that are more exposed to UV seem to have more, e.g. sun-loving vs. shade-loving anoles. In most cases that I am aware, these pigmentation layers can allow UVB penetration of the skin, which is where vitamin D synthesis takes place. There is a study of Kenyan chameleons by Al Bennett of U Cal Davis that shows that chameleons do alter their reflectivity of UVB of their skin somehow but the mechanism is not clear.
6. Since we are still in the topics of nutrition, what is your standing on the necessity of supplementing a preformed vitamin A VS beta-carotene?
I went through a period where I gut-loaded crickets with carrots but deprived them of preformed vitamin A and the chameleons developed vitamin A deficiency. This was surprising because humans can use beta-carotene for our vitamin A needs. So, I recommend using preformed vitamin A either as a direct supplement or in insect feeds.
7. Are you familiar with the reason why they cannot convert beta-carotene into Vitamin A? Also, how is it in the wild, they satisfy their need of Retinol? As a chameleon keeper, this topic seems to be controversial among people. Is there a more thorough study that addresses this matter?
I don’t know why the carotene in carrots couldn’t be converted. It could be that other carotenes in the guts of wild plant-eating insects can be. It could also be why panthers sometimes occasionally eat lizards and nestling birds, which should be a good source of retinol. I think it is a good idea to feed panthers large pinkies or small lizards, such as anoles, occasionally, if they will eat them. There indeed needs to be more study on this subject.
8. What is your recommended dosage of preformed Retinol for chameleon in captivity? Is there some kind of rules or some educated guess, for a lack of better words, to help chameleon keepers to sort out this confusion of varying degrees of nutrition requirements in an individual chameleon?
Larry Talent at Oklahoma State University gave his panthers 50 IU of retinol in corn oil solution once a week and had no A-deficiency symptoms.
9. Geophagy behaviors often found among the chameleon (Panthers and Veiled) in captivity and, unfortunately, very little is unknown of why this behavior often surface. My chameleon, regardless of all my attempts in enriching the feeder's nutrition and supplementation, is also one of the guys that practice this behavior (I sift the soil and throw away all the large lump to avoid possibility of impaction). In your opinion, what is the reason behind this behavior?
I have never witnessed geophagy or read about it, except one time. Once I witnessed a captive Parson's devour a shelf fungus that happened to be on a log in its cage. The only explanation that makes sense to me is that the animal senses some trace nutrient or mineral. A lot of lizards, e.g. geckos and Sceloporus, will lick mineral supplements out of a dish.
10. Why are there different colorations found in furcifer pardalis in different locality?
-Q Justin Carl-
The bottom line about color differences is, of course, I do not know. However, I speculate that in F. pardalis there has been a lot of population bottlenecking throughout the range and that differences among current populations in male coloration has resulted from evolution by genetic drift, i.e. I don’t think there is yet good evidence for adaptive evolutionary causes for the current differences. The more interesting color difference is the ability to rapidly change the entire head and body color during social displays in eastern populations and the more gradual seasonal changes in western populations that only allow rapid color change around the eye turrets and face. Eastern populations probably evolved in heavy rainforest habitat while the western populations probably evolved in more seasonal savannah habitat. In the east it may be more important for males to remain dark-colored most of the time to absorb heat when it is more overcast and only “brighten up” temporarily throughout their daily activity when they court or combat. Who knows? There are some interesting geographic difference in both F. oustaleti and F. lateralis. In both of these species the differences are more among the females than among the males. I think that F. pardalis, F. oustaleti and F. lateralis each represent a collage of yet-undescribed cryptic species that future taxonomists, using DNA data will discover.
11. I have always wondered about a certain behavior that chameleons display. Why do they go brighter and lighter during sleeping? In my simple reasoning, this seems to be contradictory to evolutionary behavior. Why go all the trouble camouflaging itself in the day and go bright during the night where some predators are active?
The behavior (movement, repositioning expansion etc.) of chromatophores (pigment bearing skin cells) is an energy dependent process. At night chameleons simply shut down the active process, chromatophore pigments contract, and the animal lightens. Because their natural nocturnal predators are not dependent on color vision, there has been no natural selection for them to maintain the active process while they sleep, just for them to save energy. We are new "color-vision" predators that exploit the conspicuousness that results when they are sleeping. Rest assured that should we be around long enough to exert significant natural selection, nocturnal cryptic coloration will possibly evolve in those exploited species (1000 to10, 000 generations or so down the line).
12. While we are still talking about panther colorations and locality, what are your thoughts on the practice of breeding different locality panthers?
Regarding the crossbreeding of color variants. I see no problem with herpetoculturist doing this. I have done a little of it myself. Since some of these crosses result in unsuccessful propagation, it is important in the buying, selling, trading game that it be crystal clear about which specimens are hybrids and which are not. Furthermore, if an animal is a hybrid it is important to know who the parents were, if it is a backcross etc. As genetic techniques and knowledge advances, herpetoculturists may be able to have simple genetic identity kits that allow identification of the genetic makeup of an individual of unknown history. This is still a long way off.
13. Regarding crossbreeding on panthers, many shunned the practice in defense of preserving the genetic traits and the possibility of reintroducing the specific locale species into the wild (in case the risk of extinction happened), what is your comment in regard to these thoughts?
Most of the breeding products of herpetoculture are done with the idea of the pleasures and profits of keeping herps in captivity. For this, “genetic purity” doesn’t need to be a high priority, although I think that keeping track of genetic heritage is always useful for promoting the industry and helping explain breeding anomalies. For the captivity-oriented breeders neither hybrids nor “pure” individuals should be reintroduced into wild populations because they are likely to be different genetically (i.e., more homozygous and/or possessing odd alleles or genotypes) from wild stock and could affect the natural gene pool. The idea of captive breeding with the purpose of reintroducing stock back into the wild involves different goals and dictates that breeding stock be kept as naturally pure (i.e. not hybridized with individuals from very different populations) but as heterozygous genetically as possible (i.e. not inbred). Such programs are a high priority among zoos with some involvement by universities and the private sector. Here studbooks and very rigorously controlled out breeding protocols are essential.
14. What is your advise for herp hobbyists in successful keeping of chameleon?
My advice to herp hobbyists just starting out on chameleons is to start small. Get one large juvenile or half-grown individual of a species known to be hardy in captivity from a reliable captive-breeding source. Do your homework before you purchase an animal. Make sure you are willing and able to get the proper setup before you purchase your animal. Be aware of animal's light, temperature and humidity requirements. Be prepared to devote quality time daily to your animal so you can get to know the subtle signals that all is well or not well. However, do not over-react to perceived signs of distress. Healthy chameleons are pretty tough. Bigger is not always better with regard to food, vitamin-mineral supplements, cage-size, cage-ornamentation etc. In general, plan to keep your chameleon one animal per cage. Enjoy your experience and don't be too frustrated if your first chameleon doesn't do well. Be aware that they can become addictive. You may catch the dreaded disease: Chameleophilia!
15. What next for you, Dr. Ferguson? Any new research or new books coming out?
As a new retiree from academia and having a relatively healthy 67-year old mind and body, I plan to remain active in herp research for as long as possible. My current interest is in ultraviolet light and behavioral UV-vitamin D photo regulation, i.e. increasing our understanding of how lizards and snakes perceive and utilize ultraviolet light to regulate their vitamin D-condition. I am working with the Fort Worth and Dallas Zoos and with several colleagues to focus on ultraviolet cage environments. Basically, we are collecting and using data from lizards and snakes in the wild to document the normal UV exposures in their various types of environments. From this we are establishing guidelines for setting up UV sources and gradients in larger and smaller enclosures. We are working closely with Frances Baines and Steve Makin to evaluate artificial light sources and solartech meters. We plan to establish a detailed set of guidelines for the zoo and herpetoculture community on the proper use of UVB for various species. Stay tuned for the fruits of our labors.
Thank you Dr. Ferguson for this wonderful opportunity and your insightful answers.
I wish you more success for your researches.
Cannot wait for your new books! :)
Thanks, Frans; It has been fun ! I like your blog !
Friday, March 28, 2008
Step I - III
The chameleon notice a movement. the prey is then located and determined as edible. During this step, chameleon calculates the exact position of the prey for accuracy.
II. "Localization" (see picture box #1 and 2 by Robert Salas below)
The chameleon focus both of its eyes and move slowly to close the distance between him and the prey. And, he moves slightly forward.
III. "Protrusion" (see picture box #2 and 3 by Robert Salas below)
This signified by the chameleon opening his mouth and protruding his tongue slightly. A sign that he is ready to shoot at any moment.
Step IV "Projection" (see box #1 by Paul Kartsub below)
When the chameleon is ready, its tongue will immediately be shot at a high speed toward the prey. Usually, chameleons instinctively focus to shoot for the insect's head to minimize retaliation from the prey. Once catapulted, the chameleon cannot halt the tongue in the middle of action.
Step V "Retraction" (see box #2 and 3 by Kartsub below)
As the tip of the tongue become somewhat extended in width, the tongue is then pulled backward creating a vacuum/ suction motion (think of their tongue to somewhat similar to straw). On top of the muscle that able to hold the prey, the suction stabilizes the prey preventing them to be able to break loose easily. Contrary to popular beliefs, chameleon tongue (although somewhat sticky) are covered with moisturizing agent. So, they do not depends on the stickiness of their tongue as much as they depend on gripping and vacuuming.
Notice the bent tongue in the 3rd photo from the top by Kartsub. The bent area is the point where the Hyoid bone ends.
Step VI "Consumption" (see box #4 by Kartsub above and box #1 by Kartsub below).
During retraction, once the tongue is in close proximity to the mouth, the chameleon will close both of his eyes by reflex to avoid injuries from the struggling insects.
The next step is pretty obvious. The chameleon will bite hard to deliver a fatal blow to the prey .