Understanding thermal burns in reptile patients (Proceedings)
Thermal burns in reptiles are one of the most common injuries seen by herp veterinarians. The exact reason why reptiles seem so prone to burns is not understood, but, something about their behavior makes them more susceptible to this type of injury than any other captive animal.
Since reptiles do everything slowly, it is not uncommon for an animal to get burned, but not actually show signs of the injury for several days. This is especially true for minor, or first degree burns. This is significant, since burns, even apparently mild injuries, can have severe consequences if not treated properly. In order to be able to treat burns properly, it is important to understand what causes burns, and how to recognize them in their early stages.
ThermodynamicsAs herpetologists, we are all familiar with the importance of providing proper temperatures to the cage environment. Over the years we have seen the evolution of heating devices from the original "hot rocks" to the more advanced, thermostatically controlled environmental chambers.
We have learned that not only must captive reptiles have supplemental heat, but, supplemental heat provided in the proper fashion. For instance, a fifteen foot long python would not fare well with a single, twelve inch hot rock. Likewise, a nocturnal lizard would suffer if its cage were heated with a bright heat lamp.
A look at animals in their natural environment will help us understand the principles of thermodynamics from a practical perspective. As an example, let's evaluate the heating strategies of the ever popular green iguana living in the rain forest.
These animals live for the sun. On an initial glance, it appears that they derive their energy-providing heat from basking in the sunlight. But, on closer inspection, there is a lot more involved than an animal merely perched atop a branch soaking in the sun's rays.
Before we analyze what is happening, let's take a step back and review some of the principles of heat and heat transfer. The study of heat and its properties is called thermodynamics.
In order for an object to get warm, or "heat up," there must be a transfer of heat from some outside source to the object that is being heated. Heat always moves from a warmer area to a cooler area. As the heat leaves the first object and enters the second object, the first object becomes cooler, and the second object becomes warmer. Eventually, the temperatures of the two objects will become equal. In other words, they will equilibrate. Heat will never continue to leave the first object such that it becomes cooler, resulting in the new object becoming the hotter of the two.
There are three ways that an object can gain heat, or become warmed. These are via conduction, convection and radiant heat.
Conduction is the transfer of heat within an object (such as down a long metal pole) or between two objects that are touching each other. A classic example of conduction is a pan on a stove. The burner on the stove heats up. A cold pan is then placed on the hot burner, and the heat then transfers from the hot burner directly to the cooler pan, thereby heating up the pan and the contents inside.
A herpetological analogy here is the use of a "hot rock." Hot rocks, for those not familiar with these items, are a solid, block-like structure, usually made out of brick, concrete, plaster or heavy molded plastic. Imbedded within the rock is some sort of heating coil. When the heating coil is plugged in it generates heat. This heat, in turn, heats up the rock.
If a lizard (or any reptile) crawls up on the rock, the heat from the hot rock will then transfer, via conduction, to the lizard. The path of the heat transfers from the surface of the hot rock, through the feet and belly and tail of the lizard, or whatever parts of the animal are in DIRECT contact with the rock's surface.