Keeping Captive Amphibians Healthy – bacteria, fungi, parasites and other considerations – Part 2

Click here to read the first part of this article

Salmonella spp.
A variety of Salmonella species are commonly present in amphibian digestive tracts. Many are easily transmitted to humans and can cause severe health problems, especially among the young, elderly and immune-compromised. It is essential that you discuss with your family doctor the best methods of avoiding the transference of Salmonella.

Otherwise healthy amphibians may harbor Salmonella without external symptoms. Animals suffering from an infection will usually cease feeding and become lethargic. Your veterinarian can diagnose Salmonella via blood tests (often the animal will be anemic) and fecal samples. Gentamicin and other antibiotics, methylene blue and acriflavine have proven useful against Salmonella.

Aeromonas hydrophila
This gram-negative bacterium causes many of the most commonly seen infections in captive amphibians. Usually diagnosed as “red leg” or “septicemia”, Aeromonas outbreaks cause hemorrhages leading to patches of red skin, often on the underside of the legs and abdomen. In advanced cases, the skin sloughs off, leaving large, open sores. Definite diagnosis is made by a culture of blood samples.

Aeromonas is extremely contagious and transmitted by contact between animals or with the water or substrate in which infected animals were held. Be sure to wash your hands thoroughly after handling sick amphibians and to use separate nets and other tools for each cage. A number of medications are useful in treating Aeromonas infections, but only if the condition is caught early on.
If you suspect Aeromonas, a first step might be to lower the temperature at which your pet is held. Among temperate amphibian species (i.e. leopard frogs, Rana pipiens), temperatures of 39 to 41 Fahrenheit have been used to successfully treat infected animals.

Other Bacteria
Many other ailments that commonly afflict amphibians are caused by bacterial infection. Those caused by Micobacteria are particularly difficult to treat, while Chlamydia infections usually respond well to medications such as Oxytetracycline. A. hydrophila is usually implicated it gas bubble disease, a complicated phenomenon that originates from environmental conditions. These and related microorganisms will be discussed in a future article.

Fungi are particularly adept at taking advantage of conditions, such as an unsanitary terrarium or depressed immune system, which might predispose an amphibian to attack. Fungal infections often occur secondarily to another health problem, and their presence should be suspected whatever a frog or salamander becomes ill.

Saprolegnia spp.
At least 20 species of fungi in the genus Saprolegnia have been shown to cause illness in fish and aquatic amphibians. Symptoms are cottony growths on the skin, weight loss, regurgitation, difficulty breathing and, eventually, ulcerations that resemble “red leg” (see above). Saprolegnia is nearly always present in the aquarium, and usually becomes established on amphibians when the mucous covering is removed from the skin (one reason frogs and salamanders should be held in soft nets or with wet hands only).

This fungus survives poorly at temperatures of over 70°F, and responds well to benzalkonium chloride and a number of other medications.

Free-living amphibians are host to a wide variety of parasites, often with little ill effect. However, when stressed by a poor diet or improper environmental conditions in captivity, the immune system may weaken and open the way to a more severe infestation. Also, due to the close confines of captivity, parasites have a much easier time infecting, or re-infecting, animals than they do in the wild.

Routine fecal exams are very important in identifying and controlling parasites. Many are resistant to medication while in their egg or spore stage, and therefore you must be careful to follow your veterinarian’s recommendations as to re-treatment (often a two-week interval will be suggested). Some parasites, such as Oodinium pillularia (which also causes “velvet disease” in fish), Charchesium, and Vorticella respond well to baths in a 0.6 percent sodium chloride solution, while others, such as Trypanosoma diemictyli, nearly always result in fatalities.

Vitamin and Mineral Imbalances and Environmental Factors
Amphibians are extremely sensitive to pesticides, disinfectants, and a wide variety of chemicals that are very common in our environment and even in the pipes that supply water to our homes. Also, as with ourselves and all captive animals, good nutrition provides the foundation for good health. I will address these topics in a later article. For now, you may wish to refer to an article I wrote earlier and posted on this blog – “Providing a Balanced Diet to Captive Reptiles and Amphibians”.

I have been fortunate in having had the opportunity to experiment with a number of medications and environmental approaches in my quest to learn more about maintaining amphibians in good health. In a few cases, I have met with some success. Doing so, despite my lack of medical training, has made me realize the value of observation and reasonable experimentation in this area. I’ll write more about this in my next article, but for now please remember that this area offers great opportunities for interested hobbyists.

A variety of articles on amphibian and reptile health, written by one of this field’s leading veterinarians, are posted at:

Keeping Captive Amphibians Healthy – bacteria, fungi, parasites and other considerations – Part 1

The prevention and treatment of disease in captive reptiles and amphibians has advanced greatly in recent years. Unfortunately, however, there is still a great deal that baffles us — our knowledge of amphibian medicine in particular is quite poor. On the positive side, we do know a quite a bit about the diagnosis and treatment of disease in tropical fishes, and much of the basic research behind this is applicable to amphibians.

General Notes Concerning Amphibian Health Care
Among the most important steps you can take to insure the health of your pet amphibians is to establish a relationship with a qualified veterinarian. Veterinary practices specializing in amphibian medicine, although by no means common, are on the increase. Your local herpetological society should be able to provide some leads.

Many medications designed for use with aquarium fish work well on related conditions in amphibians. Bare in mind, however, that amphibians absorb medication over a much greater area surface area that do fish — in many cases, the entire skin of the amphibian will allow transfer of the medicine. Although I have had success using certain medications in the same dosages as are recommended for fish, I always begin treatment with a 50% dilution and watch carefully for signs of stress (gasping, swimming about wildly, scratching, skin sloughing).

Good hygiene is the basic starting point for avoiding sickness, and, in some cases, even for treatment. Again, the porous nature of amphibian skin is a consideration – ammonia from waste products and other toxins in the terrarium will be absorbed through the skin if not removed.

Bottled spring water (not distilled water) should always be on hand. Salamanders and frogs suffering from ammonia or other chemical toxicity can sometimes be revived by placing them in such water and allowing it to flush harmful chemicals from the body.

Considering how little we know concerning the treatment of disease, prevention is vital. Always be sure to keep your pets in a secure, stress-free environment and provide each species with the appropriate temperature, humidity, light cycle and diet.

Amphibian skin is extremely delicate, and its mucous covering repels attacks by harmful microorganisms. Extreme care must be taken in administering injections and in handling frogs and salamanders. Amphibians should be held with wet hands only, or confined within a water-filled plastic bag when being examined. Catching a frog or salamander with a stiff nylon net may also remove some of the skin’s mucous coating and expose the animal to bacterial infection. When in doubt, use a preparation designed to replace the mucus coating of aquarium fish.

Due to the nature of reptile and amphibian circulatory systems, injections of most medications are given in the front legs. If multiple injections are needed, a different leg, and a different site on each leg, should be used. This will go a long way in avoiding damage to the delicate skin.

The details of all the medical treatments administered to your pets should be recorded. Not only will this prevent mistakes, especially when you’re experimenting with different dosage levels, but a record of what you have done will also be very useful to yourself and others in the future, and may even lead to a new discovery. Trust me on this – write it down, you will not remember in years to come!


The Natural History and Captive Care of the Black (Eastern) Ratsnake, Elaphe (obsoleta) alleghaniensis

Black Rat Snake
The black rat snake and the related corn snake, E. guttata, were among the first to become firmly established in North American herptoculture, and remain pet trade staples. At least 11 species of the genus Elaphe are found throughout North and Central America.

The taxonomy of this genus is confusing due to a wide variation in the appearance of individuals of the same species, and to the fact that different species inter-breed where their ranges overlap. The black ratsnake was formerly known as E. obsoleta, but that name is now assigned to the Western ratsnake. Recently, genetic evidence has shown that many North American ratsnakes should actually be classified within the genus Pituophis, along with the bull, gopher and pine snakes.

Physical Description
Although usually a uniform black in color, with an off-white underside, some individuals show traces of dark gray blotches and stripes. Juveniles differ markedly from adults, being pale gray and strongly patterned in dark gray or brown. Hobbyists have developed a number of unique color morphs, including albino individuals, and frequently hybridize this snake with related species. Black ratsnakes average 3 – 5 ½ feet in length, with the record holder being a giant of 8 ½ feet recorded from Westchester County, NY by noted herpetologist Raymond Ditmars.

Black ratsnakes living from North Carolina through the Florida Keys vary greatly in appearance from northern specimens, being various shades of yellow and orange in color. Formerly classified as distinct subspecies, known as the Everglades’s ratsnake and yellow ratsnake (both popular in the pet trade), they are now considered to be local color variations of the black ratsnake.

Range and Habitat
Black ratsnakes occupy much of Eastern North America – from SW New England and S Ontario to the Florida Keys and from SW Wisconsin to Oklahoma and N Louisiana. Happily for NYC-based “herpers” such as I, they are still to be found within NYC limits (parks in the Bronx and Staten Island), and in suburban Long Island and Westchester. Quite adaptable as regards habitat, they utilize forests, fields, rocky hillsides, swamps and overgrown suburban lots. It is one of many snake species drawn to farms, stone walls, trash dumps and abandoned buildings in search of mice and rats. In some habitats, black ratsnakes are highly arboreal and shelter in tree hollows.

Status in the Wild
Population levels appear stable in most areas, although the species is listed as of “Special Concern” in Minnesota and elsewhere. It adjusts well to some human presence and, if left alone, may become common on farms and near refuse disposal areas. Large scale captive breeding has removed collection pressures from wild populations.

Black ratsnakes are powerful constrictors. They tend, as adults, to focus on mammalian prey such as squirrels, chipmunks, rabbits, bats, voles, deer mice, rice rats, small opossums and similar creatures, but also take birds and their eggs. Young snakes include lizards, frogs and large insects (i.e. cicadas) in their diet.

A colleague of mine observed 6 foot-long (yellow-phase) black ratsnake attempting to constrict a white-tailed deer fawn on St. Catherine’s Island, Georgia. The fawn, which might have set a new “snake swallowing record” had it been overcome, eventually escaped.

Mating occurs from March to May, with 6-30 eggs being laid 27-28 days thereafter. Second clutches, laid in August, have been reported in captive situations but not in the wild. The eggs are secreted in cavities below fallen trees and rocks, or within rotting logs and stumps. The young, 11 – 13 ½ inches in length, hatch in 47-85 days.

The black ratsnake frequently shares hibernation dens with rattlesnakes, copperheads and other species. In some parts of the country it is known as the “pilot blacksnake” or “rattlesnake pilot”, in the mistaken belief that it guides rattlesnakes to their winter retreats.

Black Ratsnakes as Pets

With their moderate size and even temperaments, black ratsnakes make excellent pets. They are hardy enough for beginning hobbyists, and yet are so interesting that even well- experienced keepers often reserve a place for 1 or 2 in their collections.

Space and Other Physical requirements
Black ratsnakes do well in glass terrariums or aquariums which, ideally, should be a bit longer than the snake itself and as wide as possible. Be sure to secure the tank’s screen top with cage clips, as snakes are notorious escape artists. Cypress mulch or other substrates designed for use with snakes should cover the cage bottom. A reptile-safe disinfectant should be used to swab the cage floor after the snake defecates.

Rat snakes appreciate a shelter in which to hide and a bowl large enough for soaking. The water bowl should be filled to a level such that it will not overflow when the snake enters, as damp terrarium conditions may lead to respiratory and skin infections. If space permits, a stout branch for climbing and basking should be included.

American hobbyists favor a fairly “sterile” set up for rat snakes, but in Europe they are commonly kept in large, planted exhibits. Black ratsnakes take well to these, and, while management is a bit more complicated, the range of behaviors exhibited by snakes in such settings makes the undertaking well-worthwhile. I shall write more about keeping snakes in naturalistic exhibits in a future article.

Light, Heat, Humidity, etc.
Cage temperatures should range from 75 – 82 F, with a basking spot of 88 – 90 F. This species has no need for UVB light, but full spectrum lamps emitting UVA may be of some value. The cage should be kept dry at all times (see above).

Black ratsnakes thrive on a diet of mice and rats. They take readily to dead prey and should not be offered live rodents due to the likelihood of injury to the snake. Adults should be fed every 7-10 days.

Captive Longevity
The captive longevity record for this species is just over 34 years.

Although black ratsnakes will, like most animals, bite in self-defense, they are, as a whole, mild-tempered. Most respond well to gentle handling, but individual animals vary greatly in this regard. Never startle a snake by picking it up suddenly, and do not handle snakes after you have touched food animals. Future articles will deal with the specifics of handling in detail.

Breeding will be covered in depth in a future article. Except for snakes originating in the southern-most portions of the range, black ratsnakes breed most reliably when subjected to a winter cooling period. This species has been bred in captivity through multiple generations.

A number of European and Asian relatives, such as the Russian ratsnake, E. schrencki, may be kept as described for the black ratsnake. Other species referred to as “ratsnakes”, such as the arboreal red-tailed ratsnake, Gonyosoma oxycephala, have slightly different husbandry requirements. Please be sure to research potential pets carefully, as trade names can be misleading.

Additional Resources (detailed information on natural history)

Learning in Rhinoceros Iguanas, Monitors and Other Lizards – observations on zoo animals

Rhinoceros Iguana

Observant lizard keepers cannot fail to become aware of the surprising degree of intelligence exhibited by many species. In the course of my long career at the Bronx Zoo, I was fortunate to have been able to observe the learning abilities of a number of species not often available in the pet trade.

Although species and individuals varied markedly in their capacities, one constant seemed to be that all recognized and responded to changes in their normal routine. This makes sense, of course, from the viewpoint of survival, but I was none-the-less always impressed by the rapidity at which most learned.

Rhinoceros iguanas, Cyclura cornuta, and water monitors, Varanus salvator, were particularly striking in this regard. Animals in the collection for over 15 years, long in the habit of approaching or ignoring a single keeper in their exhibit for routine maintenance, would flee if 2 people entered. It took but 1-2 incidents for them to learn that 2 people meant trouble – i.e. a veterinary exam, but that 1 person meant no harm. The animals unfailingly retained this knowledge over a period of years, even without reinforcement by new events.


An interesting article on intelligence in monitor lizards is posted at:

Breeding the Pancake Tortoise, Malacochersus tornieri, in captivity – Part 2

Pancake Tortoises

Click here: Breeding the Pancake Tortoise, Malacochersus tornieri, in captivity – Part 1 to read the first part of this article.
Dietary factors are also very important in the reproductive process. Many species change their diets, often quite dramatically, prior to coming into breeding condition. Field research reports are often a valuable source of information as to a species’ native diet, so keep an eye out for them when doing your research.

And now back to some specifics concerning our flattened friends. As with many tortoises, male combat often precedes mating, and seems to spur reproductive success in captivity. Unlike most tortoises, male pancakes get along fairly well in general, but should be watched when one shows interest in breeding. A bit of fighting should be allowed, but battling males should be separated when you are not present, just to be safe.

Females lay a single large, elongated egg per clutch (rarely 2) and may produce 3-4 clutches per year. Adults tortoises provided with a varied diet need vitamin /mineral supplementation only once each week in most cases, but during the breeding season supplements should be added to the females’ salad at each feeding (calcium is particularly important at this time). Be sure also that your UVB bulbs have been replaced within the time limits set by the manufacturer, so that your pets can utilize their dietary calcium. Mating occurs most often in January and February, and the eggs are deposited in July and August, but such can occur throughout the year in captivity. Incubation may take up to 300 days (range 99-300 days). The hatchlings average 1.6 inches in length, and, in contrast to the adults, have domed shells.

Pancake tortoises often deposit eggs right on the surface, or within shelters, so check frequently lest they be crushed by the female or other animals. None-the-less, it is important that you provide appropriate laying sites, as some tortoises may retain eggs, or become stressed, if unable to find a good laying site. A container of slightly moist sand covered by a domed shelter (i.e. cork bark), often does the trick. Some keepers have noticed that gravid (those with developing eggs) females tend to climb into flower pots and other elevated sites at egg laying time – perhaps in the wild they seek higher ground?

Handle any eggs that you discover gently and bear in mind that oil from your skin can clog egg pores – powder free latex gloves are a good idea. The eggs should not be turned when they are moved, and should be re-positioned in the incubator in the same position as they were found. A commercial reptile egg incubator is the way to go when seeking to hatch tortoise eggs. A mix of vermiculite to water at a ratio of 1:1 by weight is the standard, although some success has been had with a ratio of 1:3. To obtain a 1:1 mix, first weigh the vermiculite in grams and note this figure. For the water, you will need a graduated cylinder or measuring cup that is marked off in milliliters. Since 1 milliliter of water weighs 1 gram, the computation is easy (even for one so mathematically challenged as I!) – if you are using 50 grams of vermiculite, add to it 50 ml. of water.

The substrate should be placed within a small Tupperware or similar container and the eggs half-buried into the substrate. Weigh the container, with substrate and eggs inside, and note this figure on the container’s lid. Re-weigh once each week – any drop in weight is the result of evaporation, and should be made up by adding the appropriate amount of water (i.e. if the container weighs 1 gram less, add 1 ml. of water). In the past I have used unventilated containers (opening each day to oxygenate) with some success, but the current trend is to perforate the container to allow for more gas exchange. I would agree – especially as the eggs mature and the embryos require more oxygen – just remember to watch for water loss.

Incubation temperatures of 86-89 F have worked for myself and others in hatching pancake tortoise eggs. As with those tortoise species that have been studied thus far, the sex of the hatchling is likely temperature dependent. In general, cooler temperatures produce more male tortoise hatchlings, while higher temperatures favor the development of females (the same rules do not apply to other reptiles). There is also a range at which both sexes will be produced, more or less in equal amounts, but I do not believe the exact limits of this range have been established for pancake tortoises. This is an area where pet owners can contribute greatly, so please be sure to write in with your discoveries.

There is some evidence that decreasing substrate moisture levels spur hatching, and that a nightly drop in incubation temperature (to 77 F) increases hatching success – further experimentation in this area is needed. Again, anything that you can learn will be of immense help to those interested in keeping and conserving this fantastic tortoise.


The details of 1 person’s success in breeding this species are given at:

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