The Sun

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The Role of Radiation in Herpetoculture —

The sun bathes the earth in heat and light – radiation. Our animals have evolved over millions of years in an intricate dance with that radiation. They have evolved to operate best within specific wavelengths of solar radiation – from the short UV wavelengths, thru the longer visible wavelengths and on to the longer still infrared radiation. Some species are adapted to utilize reflected radiation from the earth’s surface.

The importance of radiation in the animal’s life can not be over stated. The sun (heat and light), together with the earth (substrate), the wind (ventilation) and the rain (water and humidity), make up the four key elements to enclosure design. They can not be considered separately – they are inter-related parts of the whole.

A personal anecdote to illustrate: When I was a kid of 12 (1970!) a friend talked his dad into letting us convert the 8 foot diameter, 2 foot tall stock tank he had bought as a kid’s splash pool into a habitat for the snakes, turtles and frogs we spent our summers catching. We built an island of rock and branches and pine boughs in the center and filled the tank with 8 inches of water to form a moat around the outside. The animals we kept this way were the healthiest herps I have ever kept. Which, when you think of it, is a pretty sad indictment of our current level of captive care!

But something happened when we brought the animals inside for winter. They became lethargic, feeding slowed or stopped. The snakes developed infections on their belly scales. The turtles eyes would swell shut, frog’s bellies and legs would turn red with bacterial infections.

Even though we tried to get their captive care right, we were obviously missing key elements of care. But what amazed us was the quick return to health we would witness when spring finally came and we got our animals back outside. We used to say the sun put the wild back in them! Their activity levels would jump, their ailments would heal, their appetites would return. It was magic.

What we were seeing of course was the power of the sun to heal, to rejuvenate, to stimulate. Keepers who ignore that power – that intimate relationship herps have with the sun – will never keep their animals at peak health. Nor will they be able to observe truly natural behaviors. Every aspect of our herps’ physiological processes depends not only on solar radiation, but on proper levels and the balance of that radiation.

Reading through “The Bible” of herpetological medicine (1) drives this point home. So many of the metabolic processes that are critical to the animals growth, reproduction, nutrition, disease resistance, and social interaction are temperature dependent. They are most efficient when the animal reaches its preferred operating temperatures, and decrease in efficiency the further the animal moves away from that optimum, above or below.

It is important to note, however, that in almost all cases there are two unfortunate complicating factors for keepers. One, we really don’t know what that preferred temperature is, even though many care sheets pretend they do, and two, that preferred temperature will certainly change with the hour, the day, the week and the month.

How many times have we heard a frustrated keeper exclaim “I dont know what could be wrong, the temps are perfect!”? Of course, they dont know if the temps are perfect. The only evidence they have is a care sheet written by who-knows-who and uploaded to a web space somewhere. We try to overcome these limitations of our knowledge by better enclosure design, as we’ll see.

I want to talk briefly about some specific aspects of the radiation producing technology we use for our herps, but first I want to acknowledge where much of our current understanding comes from. Even though many of us have noticed the change brought about in our herps when they are brought outside to be reunited with the sun’s warm rays, it wasn’t until the work done by Dr Furgeson of UVB fame, and the team of experts at the Reptile Lighting Facebook group, that we really started to comprehend the how and why. We simply would not know what we now know without their years of education, research, experience and a nearly superhuman patience with persistently confused questioners like me. All of us who endeavor to do what’s right for the animal’s in our care are forever indebted.

So having said all that, we can finally talk about the specifics – which are deceptively simple:

  • Our herps need a range of temperatures to choose from
  • The primary source of heat should be overhead, incandescent bulbs
  • Although not often needed, ambient heat can be provided
  • Visible light should mimic the sun’s visible spectrum
  • Visible light should be bright
  • Natural levels of UV may be required and are often a safe bet

Of course, the devils in the details. But I think if a few simple concepts are understood, radiation design doesnt have to be rocket science. Here I want to relate these concepts. In other articles I will go into more details.

Far-Infrared, IR-C, Ceramic Heat Emitters and Radiant Heat Panels

Im going to go out on a limb and say these “radiant” heaters are the most misunderstood of the heating options we have. They dont radiate, for example! And the marketers often mis-represent how they work, and make erroneous claims about how to best use them.

First, it’s important to understand that IR-C, the far infrared radiation that ceramic heat emitters (CHEs) and radiant heat panels (RHPs) produce is not natural – it is not a wavelength the sun produces. Second, the far infrared radiation they produce does not “radiate”. It is not projected or radiated from the devices like the warmth from a light bulb is. The heat produced by these “radiant” heaters slowly passes from molecule to molecule via conduction. The majority of the heat produced floats up and away from the heat source unless it is trapped by the cage walls.

Finally, the particular long wavelength they produce does not penetrate the animal’s dermis. Unlike the sun’s warming rays (which are mostly near infrared, or IR-A), the far infrared wavelengths produced by CHEs and RHPs is not absorbed, so it is not distributed by the animals circulatory system as the sun’s warmth would be.

Our animals are not adapted to interact with, nor are they able to directly utilize the far infrared radiation produced by these devices, and so they should not be used as primary heat sources.

In the rare cases that additional heat is needed to boost ambient temps, these, along with properly used under-tank heating pads, can be useful. But even for animals adapted to night substrate heat it is better to warm the substrate thru the day with natural IR-A radiation from incandescent bulbs, then let it cool naturally at night. The re-radiated heat from the substrate, or basking rocks will, in fact, be the far infrared radiation produced by radiant type heaters, but that doesnt mean you should use them to create the substrate heat in the first place.

Near Infrared, IR-A, Incandescent / Halogen, Deep Heat Projectors

People are sometimes surprised to learn that near infrared producing lamps are used to treat a variety of diseases in hospital settings. The warming rays of the sun are in this near infrared, or IR-A wavelength and not only feel good on our skin, but are indeed healing.

Near infrared radiation passes through the outer layers of an animal’s skin, or dermis, to warm the nerve endings and the blood near the skin’s surface. The animal can distribute this warmth throughout it’s body via the circulatory system. I have often seen lizards and snakes warm their whole bodies by exposing just their heads to the warming radiation – both in captivity and in the wild. This is one way they can control the delicate, heat driven physiology of their bodies – and this is something they can not do with CHEs or RHPs.

Near infrared radiation is simply and cheap to provide. Incandescent bulbs (halogens are a type of incandescent bulb) produce near infrared abundantly. They are easy to implement in our vivariums too because they can be used with digital or manual dimmers and timers.

How and where to install them I’ll leave for another article, but as a general guideline they should be closely aligned with the UV radiation and with the visible light producing element if a light gradient is part of your design. Simply place a thermometer under the basking lamp and adjust the lamps output with the dimmer to achieve the desired basking air temps. An inexpensive thermometer gun will provide the surface temps. You can make big adjustments by just swapping out the bulb or bulbs with higher or lower wattage alternatives. Start with a 75 watt or 90 watt bulb and go from there. In the US halogen / incandescents bulbs are still available and much cheaper at the home stores than the pet stores. Look for their plant bulbs if they have phased out their general / home use incandescents.

Ultraviolet UVB

The UV spectrum of solar radiation has been shown to be important to the health of a number of captive reptiles and amphibians. We know in part why this is so, but there is much we dont know still. Snakes, for example, seem to live long, healthy lives without UV in a captive environment. This may be because snakes evolved from species that lived subterranean lives. Like some nocturnal lizards, they may have learned to survive without the UVB that is sought out by other reptiles.

At the same time, UV radiation has been shown to produce a physiological reaction in snakes, so there may be benefits to providing UVB that we are just not aware of yet.

In many lizard species the role of UVB is better understood and of unquestionable benefit.

Unfortunately, many pet branded products that are supposed to provide UVB actually do not do so at a beneficial level. I’ll cover this topic more thoroughly in another article. For now just know that reading through the guides on the Reptile Lighting FB Group will be important if you want to do whats right and not waste money.

Visible light, LEDs

The sun is incredibly bright. When we move from an interior space to outdoors our eyes adjust, our pupils contract, and the perception of the different intensities of light are diminished. We dont realize how much brighter it is outdoors.

Back when cameras were manual rather than digital I could measure the amount of light in a vivarium I built by using the cameras aperture and shutter settings. I wanted to create the same brightness in the enclosure that the animal would experience in nature. At that time it was nearly impossible to do so. Today we could do better, but the cage would be blindingly bright as we got close to the outdoor levels.

But there is reason to believe that the animals respond to at least very bright light. And of course the distribution of color within the visible spectrum might also be important. A “sunlight” colored LED light of 6000 to 7000K is often recommended. The brightness, or lumens, should be high. Unfortunately I dont think we know how bright is bright enough.

There are expensive LED lights available specifically for herps. I have used portable LED work lights that are very bright and create a “shaft of sunlight” effect in taller cages. Coupled with a halogen and possibly a UVb light we can get much closer to what the animal is adapted to than we ever could before.

1.) Mader’s REPTILE AND AMPHIBIAN Medicine and Surgery, STAHL and DIVERS, Copyright © 2019 by Elsevier Inc.

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