Amphibian husbandry for the veterinary clinician (Proceedings)
Amphibians are solidly represented as captives in both private and institutional collections. Many amphibian species are in precarious situations in their natural habitats due to environmental changes and disease. As a result, many captive populations are extremely valuable from a conservation standpoint. For all of these reasons there is currently a strong need for capable amphibian veterinarians in both institutional and private practice. An important point to understand regarding amphibians is that although they are lumped with reptiles as "herptiles", in reality they are quite dissimilar. Amphibians are indeed vertebrates and ectothermic, however the similarities end there. Generally speaking, amphibians are less tolerant of husbandry problems than reptiles. Amphibians do not tolerate temperature fluctuations readily and are exquisitly sensitive to water balance problems and environmental toxins due to the permeable nature of their skin.
An in depth description of configuring vivaria for amphibians is beyond the scope of this abstract. The interested clinician is encouraged to read more complete references such as Amphibian Medicine and Husbandry by Wright and Whitaker (2001).Captive amphibians typically do best when housed in complex, naturalistic vivaria that reflect the natural history of the species. Natural behaviors (including reproduction) are encouraged when the amphibian is able to interact with the environment appropriately. In addition, a properly constructed and stocked naturalistic vivarium will establish a biological cycle and require infrequent servicing. Alternatively, some species tolerate rather Spartan captive environments. These types of environments offer the advantages of being easier to keep clean and allow for more intense monitoring of individual animals. Hospital and quarantine vivaria are often minimalistic to allow easy care of the amphibian patient.
Large frogs and toads can be difficult to house appropriately due to their inclination to try and jump through clear barriers, which often leads to traumatic injury and infection. Enclosures need to be of appropriate size for these animals and ideally visual barriers should be employed to discourage them from jumping into the walls. Great care should be taken to avoid having sharp or abrasive surfaces in the amphibian vivarium. Amphibian skin is extremely delicate and can easily be damaged, potentially resulting in severe injury or introduction of infectious organisms.
Ventilation is important and an appropriate level is often difficult to maintain without sacrificing adequate levels of humidity (most species require around 70% humidity, though a humidity gradient is recommended). The keeper needs to tinker a bit with vivarium configuration in an effort to balance ventilation and humidity. With large collections housed in a designated room, humidifiers can be used effectively. Otherwise, manipulation of the amount of airflow in a vivarium can be accomplished by covering (or uncovering) ventilation ports, adding fans, etc. Also, addition of water features or misting systems can achieve humidity goals without sacrificing ventilation.
Basic substrate for most terrestrial amphibian vivaria can consist of a layer of pea gravel which may or may not be covered by sheet or sphagnum moss, leaf litter, mulch or soil. If simple gravel is chosen it should either be too large for the animal to ingest or small and smooth enough that it can be passed without complication. Soil is generally avoided, unless necessary to facilitate burrowing, as it typically goes foul more quickly than the other described substrates. It is best to avoid using peat moss or other acidic materials as the resultant pH of the substrate may be inappropriate for most species. Soft wood mulches (such as cedar) and those containing sharp or abrasive particles should be avoided for safety reasons. Substrates purchased from garden and home improvement stores should be free of pesticides, fertilizers and soil aerating materials such as perlite. Substrates can be collected from outdoor areas thought to be free of chemical contamination and can be treated via freezing for 2-3 weeks or heating in an oven to 200 F for 1-2 hours. A moisture gradient should be present within the substrate of the vivaria, which allows the amphibian to choose the appropriate conditions for its proximate needs. In general, substrate should be moist without being foul. Most natural substrates will need to be changed every 3-6 months to avoid bacterial build up.
In simple vivaria, the substrate can effectively consist of moistened, unbleached paper towels. The paper towels will need to be changed frequently as they quickly become unhygienic. For completely aquatic amphibians gravel or fine sand can be used as substrate or the floor of the tank can be left bare. If the floor is left bare, efforts should be made to make it appear opaque to the amphibian to discourage continual attempts to swim through it. This can be simply accomplished by placing colored paper underneath the tank.
Three basic rules should be followed when selecting furnishings for amphibian vivaria. First, the item should be free of any sharp edges or abrasive surfaces that may damage delicate amphibian skin. Second, the item should be non-toxic and easily cleaned. Third, the vivarium furnishings need to be stable so they don't fall and crush the animal. Rocks and hardwood branches can be used successfully following disinfection. Plastic items can also be used as long as they are capable of being cleaned and disinfected.
Rules for plants follow the same basic outline as for vivaria furniture. The vast majority of adult amphibians are strictly carnivorous, so there is very little potential for ingestion of a toxic plant. Secondary intoxication is theoretically possible if an invertebrate prey item ingests a toxic plant and is then eaten by the amphibian. This small possibility can be further minimized by not feeding more than can be eaten in a short period of time or providing alternative food for the insects. Plants should be selected that do not have sharp spines or other features that may injure the amphibian, otherwise selection is limited to what will survive in the vivarium. It is usually easiest to place plants in plastic pots prior to situating them in the vivarium. By leaving the plants in pots, one will not need to maintain a soil substrate in the vivarium. This approach also allows plants to be changed out without disrupting the entire vivarium.
It is paramount that captive amphibians be provided with comfortable hide areas within the vivarium. Selection and configuration of hide areas will reflect the natural history of the species (i.e. arboreal frogs will not use a cave on the substrate). Multiple hide areas within the temperature, humidity and light gradient should be provided. Most animals will choose perceived security over other appropriate environmental parameters. Amphibians without satisfactory hide areas often do poorly. Along this same line, amphibian vivaria should not be placed in high traffic areas in order to avoid stress due to excess noise, vibration and light. Many times a beautifully constructed, appropriate vivarium is rendered inhospitable by being placed in the family room where constant activity and erratic light cycles cause disruption of normal behavior and stress.
Amphibian enclosures need to be escape-proof. Many captive amphibians have succumbed to desiccation following escape from their vivarium. Tight fitting lids are a must. If a large collection is housed in a single purpose room it may be advisable to place small humidity retreats on the floor so that potential escapees may seek refuge and avoid desiccation.