Introduction

Amphibia is a fascinating class of animals, with three orders: Anura (frogs and toads), Caudata (salamanders, newts), and Gymnophiona (caecilians). There are ~ 7,000 known species in this class. At first thought, this seems overwhelming; however, 90% of those species are frogs. Amphibians can range in size from 7.7 mm to 1.8 meters.¹ Obviously the scope of a one-hour lecture cannot cover all aspects of all species of amphibians. Instead, focus will be placed upon the more commonly kept (and therefore seen by veterinarians) species that are seen in USA pet stores or in some cases show up from the wild. There are also some basic generalities that can apply across similar species. Encourage clients to do an immense amount of research before getting an amphibian pet and have the enclosure set up and running smoothly before actually taking possession of the amphibian. Have them refer to multiple sources, not just the pet store, a book, or a single website. Amphibians are not good beginner pets.

The most common species kept in captivity include African/dwarf clawed frogs (also called Xenopus), American bullfrogs, various true toads, fire-bellied toads, green tree frogs, leopard frogs, marine toads, poison dart frog species, White's/Gray's tree frogs, red-eyed tree frogs, ornate (Argentine) horned frogs (Pacman frogs), monkey tree frog, Mexican axolotls, tiger salamanders, and newts. Amphibians may be categorized as tropical vs. temperate, terrestrial vs. aquatic, anuran vs. caudate.

As you see more amphibians, your practice may want to develop species-specific handouts on husbandry/diet. However, there are also excellent resources to direct clients to; just make sure you agree with all of the statements contained within and that you provide proper credit to the source. Petco®'s website can be a good starting point for the species they sell - www.petco.com/CareSheets/petco_CareSheets.aspx#Amphibians - though in no way should this be misconstrued as an endorsement of the company. More in-depth resources can be found at various sites, including www.amphibianark.org/%20resources/%20amphibian-husbandry/husbandry-documents/, and arav.org/links/. Even more advanced information can be gleaned by reading journal articles or books describing the natural history and environment of the species.

Water Quality

For most commonly kept species, whether aquatic or semi-aquatic, this is the most important aspect of husbandry. Avoiding metal piping or metal items in the enclosure can be important to avoid heavy metal toxicities. This also means that it is a good idea to collect tap water after the faucet has been running a bit, to flush out loose particles of those metal pipes. Most clients will utilize tap water. While there can be some variations in certain water quality parameters based upon time of year, for the average client, this should not be significant. What is important is for the client to collect water, dechlorinate it (using fish aquarium products or by letting it sit in a container that can aerate well if it has chlorine vs. chloramine), then test this water. In some cases, a human water-quality testing kit available at many home improvement stores/websites can be useful because it tests for copper, iron, pH, hydrogen sulfide, hardness, alkalinity, nitrite, and nitrates. This type of test runs about $10 and should usually only be run initially, if a new water source is to be used, or if problems suggest this should be retested. Hardness of water can be a major concern, especially if water softeners or filters are used, so this parameter may need to be checked more regularly depending upon species and water source. Otherwise, an aquarium master water-test kit should be purchased from a pet store (the type used to test water for housing fish), with the water tested weekly for ammonia, nitrite, nitrate, and pH levels. Most of the chain pet stores also provide free water-quality testing if a sample is brought in, though this can become time consuming. Amphibians often tolerate slightly acidic pH better than alkaline, but be careful about extremes or extreme switches. Ideally, there should be no ammonia, no nitrites, and no or low nitrates. Most clients will hopefully use and definitely need a closed filtration/pump system for the water, appropriate to the organic debris load and water quantity. While more terrestrial species such as tree frogs, toads, and salamanders may be easier to provide a stagnant, non-filtered water source, these need to be changed and disinfected, often daily.

Enclosure

Amphibians have a thin epidermis (though a relatively thick dermis), which can be easily abraded by rough substrates. I generally prefer sphagnum moss (not the block form, but the actual moss form) and large smooth rocks (be aware that rocks can also affect water hardness in a good way) as a recommended substrate. Soil, moss, and other natural substrates are very good places for bacteria and fungus to grow and are more difficult to clean, so change them out weekly to monthly. Opaque hide boxes are important. If a climbing species, provide climbing objects, but remember there is no good way to fully clean wooden items, and they should be periodically thrown away and replaced. Also make sure these items are well secured so that they do not fall and injure the amphibian. The larger the cage, the better; however, this can be problematic for many novice amphibian owners. Plastic versus live plants are often good for starting out. Remember that introducing natural items like soil may also introduce undesired contaminants, so clean and sterilize before using. Most amphibians are best kept by themselves or in small numbers of the same species. Mixed species exhibits are complex and challenging to maintain and should be discouraged for new pet owners. Never mix species from different countries, to prevent exposure to new diseases. Encourage an examination and some level of quarantine before adding a new individual to an enclosure already housing other amphibians. Excessive handling while they are new should be avoided and the owner should be encouraged to use nitrile gloves moistened with "frog water." Some amphibians are 100% aquatic, while others are best kept in a more balanced environment. Most need lots of humidity (even desert species), but humidity also increases bacterial, fungal, and algal growth. Clean all bedding out on a weekly basis and scrub all cage furnishings monthly. One can use a dilute bleach solution of 1/8th cup of bleach to gallon of water for removable items, rinse copiously, and dry well (bleach is ineffective on any wood type products).

Heat and Light

A UV light is necessary and should provide 2–8 hours of light (use a timer to keep this regular) with 2–5% UVB, not being screened by plastic/glass/mesh, and within 24 inches of the amphibian. There are numerous anecdotal descriptions of UV burns in both reptiles and amphibians, so it is important to provide options to get out of the light and still be in preferred locations (high perching for tree frogs for example). For heating, generally avoid heat lamps (some of the non-fluorescent UVB bulbs also produce heat) and heat rocks. Use instead an aquarium heater for the water portion if needed and an under-the-cage heating pad for the land section. Amphibians have a bigger problem with too hot than too cold. Remember that rule especially when transporting in the summer! The following are general rules for temperature ranges. Have at least 2 thermometers - one in the water and one on land. Always use digital thermometers only and preferably a temperature gun directly on the amphibian. Temperate salamanders keep at 50–61°F, tropical salamanders at 58–68°F, temperate frogs at 68–77°F, and tropical frogs at 77–86°F. As you can see here, with some species, a cooling device is necessary! Remember some pumps for filtration can produce significant amounts of heat directly or to the water. Also remind clients of the effect window heat can have with cage placement and that summer/winter house temperatures can vary significantly.

Diet

Nutrition is a constantly evolving science, and the veterinarian and the owner of the pet need to keep on top of changing information. Trying to recreate wild diets in captivity, especially when food type variety may be limited by season, cost, availability, or owner laziness, can be extremely challenging. Nutrition recommendations for many exotic animal pets often revolve around the recommender's experience and opinions versus hard science, more than any other aspect of veterinary medicine. One of the most frequently asked questions by clients to veterinarians (for which guidance in answering is rarely provided) is "How much and how often?" to feed. There are so many variables that affect the answer to this question that many veterinarians freeze up on the answers. Age, sex, season, size, reproductive status, nutritional value of the food item, and ecdysis status, among others, need to be considered. The metabolism of an amphibian is much lower than for a bird or mammal. The concept of feeding weekly or monthly for certain amphibians cannot be easily grasped by many owners, who instead overfeed their pet. Variety is important, but may be impractical. Enrichment is an often overlooked but important factor in avoiding anorexia or obesity. All amphibian owners should use a gram scale to weigh their animal at the same time each week to note trends. Post-eating, post-urination, or post-defecation are not necessarily good monitoring times. Weight decreases of 20% should be worked up, while healthy weight gains in a growing amphibian can be variable. Knowing the correct body condition for each species is important.

Most amphibians are insectivores. Here, the adage, "You are what you eat" comes into play. Insects themselves are generally nutrient deficient, with the exception of their stomach contents. Wild-caught insects are generally "ready to eat" meals, while most captive raised invertebrates require supplementation before feeding them to amphibians. "Variety is the spice of life" is true for all reptiles and amphibians, but especially so for the insectivore. Unfortunately, the option to purchase invertebrate variety is often limited. Many amphibian owners are encouraged to develop their own "farm" to raise invertebrates. I recommend high-quality soil/mulch with added Tums® for earthworms, leafy greens and red/orange/yellow vegetables for roaches and crickets. I no longer recommend feeding mealworms, superworms, or waxworms (they are fat, vitamin E, selenium, chitin and not much else, though they sure seem to taste better to the insectivore). However, allowing these "worms" to metamorph into beetles does allow for a better nutritional product but requires more work. Convincing evidence of the benefits of "shake and bake" application of vitamins and minerals before feeding an invertebrate is not strong and often causes palatability issues. Live invertebrates are always recommended versus some of the canned or dried versions available at this time. Be especially careful to avoid offering invertebrate gel diets or water gel, as I have seen several cases of amphibian ingestion of the product and subsequent gastrointestinal rupture or blockage leading to death. Invertebrates also can do a lot of external damage feeding on their predator, and the stress of the constant presence of food items in a confined space can also be detrimental to the amphibian. Feed only the number of invertebrates that can be eaten within 15–30 minutes and remove any left over to be offered at a later date. Feed immature animals more frequently and adults less frequently. Feed smaller items that will be easily ingested more frequently. Those amphibians that sit most of the time waiting for prey only need to be fed a batch of invertebrates weekly to even monthly, while those constantly chasing invertebrates and requiring higher amounts of energy based on their metabolism (poison dart frogs), should be fed daily.

Other Information

In most cases, privately owned amphibian health issues can be traced back to improper husbandry or a condition caused by a breakdown in a properly set up enclosure. So an extensive part of the examination should include probing husbandry questions and ideally either a house call or a photo/video of the enclosure and its management. The captive life span is unknown for many species, although some can live for 40 years plus and many into their teens. Most commonly kept species can live 10–20 years if cared for properly. Sexing can be challenging, especially before maturity or if there are not several individuals of the species to compare. In anurans, males often have a nuptial pad on the thumb for holding on during mating and are the primary vocalizers. Male salamanders have an enlarged cloacal region when reproductively active. Some species can be sexed by overall size differences (males usually smaller in anurans), by size of crests, and even by color. Yes, they can and do bite, and it can hurt!

References

1.  Amphibian [Internet]. Wikipedia [cited 2015]. Available from en.wikipedia.org/wiki/Amphibian.