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Introduction

Over the past few months I have seen an increasing number of problems associated with the use of heat mats and so it seems appropriate to re-iterate the proper use of these heating devices and to describe the health problems that can arise from improper use or the use of faulty mats. Generally speaking, heat mats are a valuable item of equipment which are relatively inexpensive, durable and provide gentle warmth over a large area. There are two makes commonly in circulation, the Microclimate and the Ultratherm range. In my experience both makes have similar advantages and similar disadvantages if used incorrectly.

Using Heat Mats

Heat mats are, by design, low wattage heaters, however, the surface temperature can often exceed 49°C (120°F) if they are uncontrolled, and therefore the recommendation for placing these mats under the vivarium or inside against a back wall is a sound one. These mats are particularly prone to overheat if they are insulated (for example, covered with excess floor substrate, or placed under the vivarium) and in all cases it is advisable to use a thermostat or rheostat to prevent the surface temperature from exceeding 35C (95°F). The use of under-floor heating replicates a natural night time phenomenon as heat absorbed by the Earth during the day is released at night.

These mats are, therefore, most useful as a means of providing gentle background heating, particularly at night. They are least useful as a basking site for species which are active by day and naturally thermoregulate by basking under a radiant heat source. It is also important that the mat does not exceed half the area of the vivarium, as the reptile may have difficulty in locating cooler areas and consequently overheat. Heat mats do not make ideal basking areas for chelonia or the larger species of lizards and snakes, especially if an adequate air temperature is not maintained. In such circumstances, the reptile will often spend excessive amounts of time on or against the mat in an attempt to thermoregulate. Excessive contact between the reptile and the mat leads to the mat overheating, with consequential skin damage and disease (dermatitis).

Skin Disease Due to Heat Mats

All cases of skin disease that I have seen associated with heat mats have involved chelonia of any size or snakes and lizards over 1 kg in weight. In all cases captive husbandry, particularly hygiene, was adequate but the heat mats were placed on or under the floor of the vivarium.

The first example involved a 1.8 kg royal python (Python regius) which was maintained on a two-foot mat which was placed inside the vivarium under newspaper. The heat mat was not controlled by a thermostat or rheostat. The snake had been successfully maintained using this system for several months. However, a recent meal coupled with a drop in the ambient room temperature forced the snake to bask excessively on the mat which resulted in a thermal burn. The damaged skin quickly became infected with Pseudomonas aeruginosa which led to a severe bacterial dermatitis. The snake presented in a state of lethargy and dehydration with severe ventral skin damage and infection (plate one). The snake was sedated to permit removal of all the dead tissue (surgical debridement). The wound was then cleaned using an iodine-based antiseptic (plate two). The snake made a good recovery on fluid and appropriate antibiotic therapy and daily cleaning of the site with Tamodine (Vetark). This snake survived the ordeal but nevertheless remains extensively scarred and will undoubtedly suffer shedding problems (dysecdysis) for many months to come. The owner was instructed to place the heat mat under the vivarium, and to provide a radiant, overhead, heat source, with both heaters to be controlled by a reliable dimming thermostat.
 



A second case involved a 900g Horsfields tortoise (Testudo horsfieIdi) which was maintained on a heat mat that was placed inside the vivarium and under newspaper. The heat mat was controlled by a pulse thermostat with the probe reading the air temperature not the surface temperature of the mat.

The owner noticed that one of the ventral scutes appeared loose and presented the tortoise for veterinary examination (plate three). Once again it was necessary to sedate the reptile and debride the wound, which meant removing all the ventral scutes and removing all infected tissue (plates four and five). Once again there was a secondary bacterial infection which responded to appropriate antibiotics. Chelonia, those terrestrial species (Testudo sp), thermoregulate by angling their carapace to the sun (or radiant heat source in the vivarium). The heat mat method of providing a daytime basking area is, therefore, unnatural and the owner was advised to change to an overhead ceramic heater controlled by a thermostat.
 



The final case involved a Madagascan Hognose (Lioheterodon madagascariensis) snake which was originally presented with a damaged tail. The snake was admitted for anaesthesia and surgical amputation of the tail. The operation was a success and the snake was discharged with instructions to keep the snake at the upper end of its preferred optimum temperature zone and to provide a large basking area of 32°-34°C (90°- 94°F). The owner provided the snake with additional heat in the form of a heat mat. The snake had a greater requirement for heat after surgery which led to excessive use of the heat mat. Several days after returning home, the snake died suddenly and on close inspection had suffered extensive ventral burns which had become infected (plate seven) and resulted in septicaemia and rapid death.
 



Heat mats are, like other items of heating equipment, open to mis-use and abuse which can have deadly affects on the reptiles that they are supposed to benefit. In general these mats are safe when used in accordance with the manufacturers’ guidelines but efforts must be made to measure their surface temperature and ensure their suitability for the species in question. The use of artificial turf appears to have advantages over newspaper if a heat mat is placed on the floor inside the vivarium. The bristles of the artificial turf seem to help reduce the chance of skin disease by supporting the reptile’s body above the heat mat and allowing air ventilation under the reptile’s body.

In summary, the following guidelines are not definitive but may help prevent problems;
 
  • Only use heat mats for suitable species, for example, they are not suited to chelonia or large snakes and lizards.
  • Use a heat mat of the correct size, that is, the heat mat should not exceed 50% of the vivarium floor, ceiling or back wall area.
  • Place heat mats under the vivarium or attach to the vivarium wall, ceiling or under platforms. If the mat must be placed on the floor inside the vivarium, regularly monitor surface temperatures and consider artificial turf as a floor substrate.
  • Always use a rheostat or thermostat (with the probe on the basking area) to prevent the surface temperature from exceeding 35°C (95°F). Some desert species may benefit from a higher temperature basking area - but check species-specific information first.
  • Do no bury heat mats under floor substrates.
  • Check the heat mats function regularly.
  • Maintain a high degree of hygiene as a damp/dirty heated floor will quickly result in a great deal of bacterial contamination that will be in direct contact with the reptiles contained in the enclosure.
If you notice a burn (from any heat source) on a reptile, it is important to remember that these wounds need surgical debridement and antibiotic therapy.

Before you manage to seek veterinary help however, there are certain actions that you can take to maximise the reptile’s chances of recovery.
 
  • If the thermal insult is noticed immediately, place the affected portion of the reptile under cold running water for several minutes.
  • Thoroughly clean the vivarium and replace all floor substrate with clean kitchen towels or newspaper
  • Gently clean the reptile’s burn with a dilute Tamodine solution.
  • Correct the heating fault or place the reptile in another prepared vivarium at the species-specific preferred optimum temperature.
  • Place a large water bowl near the basking area to increase air humidity and reduce the likelihood of the reptile dehydrating.
  • Seek veterinary assistance for wound debridement and antibiotic cover

    Author: Stephen Divers BSc(Hons), GIBiol, BVetMed, MRCVS

Published with the kind permission of the Reptillian Magazine.
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