NomadOfTheHills wrote:While there is little inherently wrong with heat rocks, you just need to monitor the temperature, as older models were known for hot spots, which can burn lizards, who are "too dumb" (not really, there are physiological reasons for it but I digress...). Don't rely on the repticontrol that is built in, use a second thermometer to check the temps.
Little inherently wrong John?! What studies can you site that led you to that conclusion? I'd like to read them. Have you seen any photos of animals with thermal burns from direct contact heating devices? You are correct that it is physiological, all physiological. These animals don't need localized ventral heat. And you can't possibly monitor a heat rocks' temp 24/7. The cheap wafer type thermostats they put in these heat rocks stick, and just like any of the cheap thermostats, and it's when it will stick, not if. And just how do you monitor the temp of the rock surface while your lizard is on it?
First a fact about reptile heat absorption; they sense heat from above. They absorb most of their body heat through the capillaries on the dorsal side of the body, not through the ventral side. The ventral area of reptiles is highly insensitive to heat, thus the many cases of thermal belly burns to reptiles with heat rocks in their cages. When a reptile gets on a hot rock or asphalt in the wild, the area it's on begins cooling immediately because he's blocking the sun that heated the area, and he's absorbing heat safely from the sun through his dorsal capillaries. A hot rock keeps pumping out the heat. The ambient temperature in close proximity to the heat rock is what attracts them to it, it being the warmest area. And, he's going to just sit there trying to absorb heat from above
Tony, I'm going to post, though I don't know why, some articles I've collected over the years, written by herpetologists, DVM's, and curators in the hope it will save some animals from a very traumatic and painful experience, and maybe even death due to the lack of knowlege and experience of the keeper. You can do what you want with it, either learn, or disregard it. The best thing you can do, is more research on your own.
A blanket statement, like John's above, is going to mislead new young keepers to believe these things are safe for reptiles. They are not. But, then again, what do I know? I'm not attempting to bash you John, but apparently, I don't have the many years of study and practical experience with reptiles that you do. Because It seems that any information I post is immediately argued against by you without backing up your "opinions" with documentation.
Opinions on forums are great, when it comes to setting up cages, decorations, substrates, and variations in food options. That's what we come here for. But opinions are not going to change the physiology of the animal. That's set in stone.
I only try to pass on things that I have personally researched from documented material and studies. I don't guess at it, nor claim to be the expert on it, I'll quote you the doctor or the study source, and let you consider them as the experts on the subject.
So Tony, here’s a few articles that I hope will help you understand a little more about heat absorption in reptiles............
Stephen L. Barten, DVM
From his Burns chapter, in Reptile Medicine and Surgery (Douglas Mader, DVM, ed. W.B. Saunders. 1996. pp. 9-19).
"Thermal burns may result from any source of heat. Heat sources that allow direct contact between the captive reptile and t he source, such as hot rocks, heating pads, or spot lights within the cage, are most often implicated in burn cases. Burns may be prevented by keeping heat sources outside of the cage or shielding them to prevent contact with the captive reptile. Backup thermostats should be wired into the system in case the primary thermostat malfunctions."
Clifford Warwick, Director, Institute of Herpetology and Phillip Arena, School of Veterinary Studies
From their Miscellaneous factors affecting health and welfare chapter, in Health and Welfare in Captive Reptiles (Clifford Warwick, Fredric L. Frye, and James B. Murphy, eds. Chapman & Hall, London. 1996. pp. 263-283).
"An example of apparent but almost certainly misunderstood physical insensitivity and poor thermal environments concerns thermal burns, which occur when captive reptiles come into direct contact with heat sources while attempting to raise their body temperature to preferred levels. The general problem may be exacerbated somewhat by ambient temperatures that are too low and which result in animals being forced to raise their body temperature through extreme proximity to heat sources (J.B. Murphy, pers. comm.). Damage from thermal burns ranges from minor lesions and scarring of the skin to extensive injury such as fusion of the eyelids or burns that extend deep into the body tissues (Frye, 1991a). These injuries may lead to permanent defacement, disability or death.
"The point of particular interest here is that the individual may appear to be oblivious to gross trauma during the period of damaging injury, and in fact insensitive to pain. One current view is that these burns arise after an animal has rested against an inactive heat source, which is then activated and beats up rapidly, causing tissue and presumably local neural damage (Frye, 1991a). Anecdotal accounts suggest that reptiles also settle on already active heat sources and then suffer burns. We propose that a major reason for this behaviour is twofold. First, a large reptile may not be able to attain an optimal body temperature from a small intense heat source such as a lamp. Second, thermal provisions in captivity fail to simulate adequately the thermal diversity of the natural environment.
"In nature the thermal requirements of, for example, a heliotherm are satisfied by a radiant solar source which bathes the entire animal with heat. However, the efficiency with which a body absorbs warmth depends on not only its own properties but also other factors including the intensity of the heat source, the position of the body with respect to the heat source and the proximity and properties of other reflective surfaces (Geiger, 1959). Thus a thermally receptive body is subject to thermal inputs of a multidimensional and heterogeneous nature. Different regions of a reptile's body have different absorbency spectra and thus different heating rates (Heatwole and Taylor, 1987). In captivity, often the only source of heat available is one or two small and usually intense heat lamps. In order to raise their body temperature, reptiles move toward a heat source and bask. Especially where large reptile species and individuals are involved, with associated slower blood circulation (Coulson and Coulson, 1986) and thus heat dispersal, these animals must attempt to raise the temperature of the entire body using primarily diminutive heat sources. Thermal absorption is attempted while continually losing warmth from body surfaces that are not exposed to the heat source and which may, indeed, be in contact with 'cold' surfaces that conduct heat away from animals.
"Compensatory behaviour may include moving closer to the heat source where upon the peripheral nerve endings are damaged and desensitized. Once this occurs, the reptile moves closer still and eventually contacts the heat source in an attempt to raise its body temperature to an optimal level, a point it may never achieve. Thus an unnatural thermal environment and related 'biological confusion' may result in thermal burns. Clearly, more data are needed to clarify the reasons behind this aberrant behaviour, especially in consideration of body size and associated heating requirements of reptiles. If this hypothesis were supported, heliotherms of a small body size in particular, would be less likely to suffer thermal burns because a heat lamp is, to them, a relatively expansive source that may more appropriately 'saturate' their bodies entirely.
"Related considerations include the fact that large lizards are more reflective of solar radiation than smaller individuals (Norris, 1967) and that they heat and cool at a slower rate as a result of a low ratio of surface area to volume. Snakes, by the very nature of their morphology, may be compromised by inadequate thermal provisions."
Susan Barnard, Curator
From her book, Reptile Keeper's Handbook, Chapter 3, The Captive Environment (p. 26; Krieger Publishing Co., Melbourne FL, 1996).
"Snake usually tend to maintain lower body temperatures than do lizards from the same geographical area, and tropical reptiles generally have less tolerance for low temperatures than those from temperate regions. Some reptiles, especially, tropical forest dwellers, may not display heat-avoidance behavior. Do not, therefore, expose these reptiles to basking spots where temperatures would rise above their selected body temperature. Keep all heating devices on the cage exterior to prevent accidental burns. I do not favor heating devices that require animals to make contact for warmth. Such devices do not increase the surrounding temperature, but provide dangerously localized heat on an animal. Reptiles can suffer burns before they become aware that they have been injured when thermostats are set to high or when they fail altogether. Conversely, thermostats that fail may produce no heat at all, and tropical forest dwellers may develop respiratory problems when temperatures fall below the range that is best for them."
Sean McKeown, Curator of Reptiles
From his General Husbandry and Management chapter, in Reptile Medicine and Surgery (Douglas Mader, DVM, ed. W.B. Saunders. 1996. Pp. 9-19).
"Historically, the hot rock has been the most misused heating source. It should never be used as the primary heat source. Hot rocks are made of clay, cement or hard plastic molded or formed around an electric resistor (heating coil). As the electric coil heats up, so does the surrounding mold. The reptile is expected to crawl on or coil around this rock and maintain its body temperature. These rocks do not heat the captive environment.; therefore, a reptile housed in a terrarium heated only with a hot rock will not have the proper warmth to meet its metabolic requirements and may receive sever e burns. Hot rocks are only effective when buried under the substrate an used as a secondary heat source. Most do not have any built-in means to control their temperature output, resulting in an "all or none" heating system. Although these have somewhat standardized construction, they typically vary in size and heat production. What may be an appropriate size and temperature for a large python may be dangerously hot for a small kingsnake. Likewise, a small, buried hot rock suitable as a secondary heat source for a small snake would be less effective for a large-bodied snake. Hot rocks are also notorious for having surface "hot spots" that can reach such high temperatures that severe thermal burns can result. Hot rocks are suitable only for ground dwelling species of snakes and must be insulated from the live animal."