Burns in reptiles and amphibians (Proceedings)


Burns in reptiles and amphibians (Proceedings)

Oct 01, 2008

In review, means by which reptiles & amphibians can become warmed is:
1. Radiant heat - The animal absorbs the electromagnetic radiation from the sun/heat element.
2. Convective heat - The warm air/water that blows/flows across the animal.
3. Conductive heat - from sitting on a basking spot that has been warmed by the sun/heating element shining on it, or from within in the case of a heating pad/rock. The basking spot/heating pad/rock then acts as a conductive heat source, passing the warmth back into the animal resting on it.

The best type of heat source for a captive pet will depend on the type of animal being housed. As mentioned, a small heat rock would be inappropriate for a large reptile. These animals do better with convective or radiant heat. Likewise, a big heat lamp would not be proper for an arboreal animal which would normally get its heat from either conduction or convection.

There are several other variables that play important roles in heat transfer and warming. A big factor is humidity. Moist air, or high humidity, tends to hold heat much better than dry air. When figuring temperatures and thermal gradients careful attention should be paid to humidity. A hot, humid cage will be much more stifling than a hot dry cage.

Ventilation is very important in any cage design. A well designed cage will have good ventilation. Stagnant air, especially in hot humid cages, leads to build up of pathogens, or disease-causing bacteria and fungi. Proper ventilation will dilute out any potential problem before it reaches concentrations that may be dangerous.

However, for all the good that proper ventilation does, it does have its drawbacks. A well ventilated cage tends to lose heat and humidity (it gets exhausted outside). There is really nothing wrong with this, except that the heat and humidity needs to be replaced, and, in the overall scheme of design, it ends up costing more to maintain a steady state of temperature and humidity. Thus it can be seen that there is a very close relationship between temperature, humidity and proper ventilation. This relationship must be considered when trying to provide the proper husbandry for the various species of reptiles & amphibians being kept in captivity.

Thermal Tissue Injury due to Heat Transfer

Of the three types of heat transfer, the two that cause the most injuries are radiant heat and conductive heat. "Hot Rocks" have been the direct cause for a great number of thermal injuries. These crude heating devices have a variable heat output. The heat is often unevenly distributed over the surface of the rock, resulting in hotspots that can reach temperatures that can burn due to direct/prolonged contact through the scales and will sear the flesh off any animal that rests on it. Not to mention that these heating devices can "short out." And, in a worst case scenario can result in a fire. Heat lamps have also been the cause of many radiant thermal injuries. Either due to prolonged or to close (but not direct) contact with the heating element. Humans have a withdrawal reflex. When we touch something hot, without any cognizant thought, we automatically, immediately, withdraw our hand. Even young children and mammals display this reflex. I have touched some brand new hot rocks, and their surface has been so hot, that I have experienced the same withdrawal reflex. They are so hot, I could not physically keep my hand on their surface. Why then, when a reptile rests on such a hot "hot rock", do they not also immediately jump off? This question does not have an easy answer. It is not uncommon for a snake to wrap its coils around a bare light bulb because it is attracted to the warmth that the light emits. So, it must feel the warmth, why then, does it not feel the burning heat? One possible answer is that the nerve receptors that sense heat and the receptors that sense pain are different. It is possible that, since in the wild, such pain receptors have no evolutionary significance (reptiles & amphibians do not normally come into contact with intensely hot objects in the wild). Therefore, evolutionarily, there would be no reason that a reptile or amphibian should have a hot-pain withdrawal reflex. Other possible theories put forth suggest that since reptiles & amphibians do not "reason" in the same fashion that people or other mammals do, even though the herptiles may feel pain, they do not associate it with the object that they are touching. Hence, they do not realize that they need to move in order for the pain to subside. Bottom line is, at the present time nobody really knows. So, until we understand why these animals are so prone to burns, the best thing to do is make every effort to prevent the burns in the first place.