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The Natural History and Care of the Blue Poison Frog, Dendrobates azureus (tinctorius) – Part II, Care in Captivity

Dendrobates azureus (tinctorius)
To read the first part of this article, click here.

General
This and other poison frogs are among the most interesting amphibians of all to keep in the terrarium. They are colorful, active by day and quite willing to display a wide range of complex and fascinating behaviors when kept properly. No other group of amphibians exhibits such a variety of social interactions that can be so easily observed in captivity.

Please note that the blue poison frog has been re-classified as a color phase of the dyeing poison frog, D. tinctorius, and is no longer considered to be a distinct species. I have retained the scientific name D. azureus in the title as it is still commonly used in the pet trade.

Space and Other Physical Requirements
Blue poison frogs do best in a terrarium heavily planted with ferns, moss and moisture-loving plants such as Philodendron, Epipremnun and Pothos. Rather than hiding the frogs from view, a densely planted tank will actually provide you with more opportunities for interesting observations, as the frogs will feel secure and will behave normally. In barren terrariums, they become stressed and remain inactive.

Live plants also assist in breaking down waste products. If you pay close attention to small details such as spot-cleaning, you may be able to maintain your terrarium more or less unchanged for quite long periods of time – several of my own have not had a substrate change in 10-12 years (note: these are heavily planted and lightly stocked with frogs). Small land snails and isopods (sow bugs) are valuable scavengers and go a long way in maintaining terrarium cleanliness. Poison frogs are very aware of their environments, and do best when left undisturbed by major terrarium renovations.

The substrate should hold moisture and support plant growth. A mix of Jungle Earth Reptile Bedding, Coconut Husk and peat moss, with a bit of topsoil mixed in, works well. A layer of gravel at the bottom of the tank will assist with drainage. Sheet moss or Compressed Frog Moss should cover the substrate to help retain moisture.

A screen cover secured by clips should be used – despite being terrestrial, poison frogs climb well and will escape through even the tiniest of openings.

In addition to standard aquariums, these frogs may also be kept in Exo terra glass terrariums and similar enclosures.

Poison frogs do not swim well, and drown quickly in deep water. De-chlorinated water of ½ inch or so in depth should provided in shallow bowls or a small, sloping pool can be created in one corner of the terrarium. The pool can be cleaned by sopping up the water with paper towels or, if large enough, may be filtered with a sponge filter.

Despite their small size, poison frogs need quite a bit of room – more so, and with many visual barriers (plants, logs, etc.), in a group situation. A pair or trio can be kept in a 10 gallon aquarium, or up to 10 in a 55 gallon tank.

Light, Heat and Humidity
Although diurnal, poison frogs do not require high levels of UVB — in fact, their skin is equipped with a UVB “filter” of sorts. However, live plants do best with full spectrum lighting. Therefore, the terrarium should be lit by a low-UVB output fluorescent bulb, such as the Reptisun 2.0. In my experience, this bulb provides enough light for most plants, and yet does not lead to the cataract and other problems seen in amphibians that are exposed to high UVB output bulbs.

Humidity should be high at all times (80-100%), but fresh air flow is essential. Therefore, you should not increase the humidity level by covering a portion of the screen top with plastic. Keeping the sheet moss layer damp and spraying the terrarium heavily in the morning and evening should suffice. If your home is unusually dry, consider installing a small mister.

Daytime temperatures in the terrarium should range from 75-82 F (a heavy cover of plants in one area will provide shade and a cooler area for the frogs) and can dip to 73 F at night. A fluorescent light may provide enough heat – if not, install a 25 watt incandescent bulb but be sure to monitor the temperature and watch that the tank does not become too dry.

Feeding
Proper feeding is the key to maintaining poison frogs long-term in captivity. In the wild, they feed on a wide variety of invertebrates. Unfortunately, the tiny size of these frogs makes it difficult for us to provide them a varied diet, and too often they are forced to subsist on only one or two items. Please remember that crickets supplemented with vitamins do not provide an adequate diet, and strive to include as many of the following as possible to your frogs:

Flightless fruit flies – cultures are available commercially; these can comprise up to 50% of the diet.

Pinhead and 10 day old crickets – these are poison frog standards, but should not be used exclusively. Be sure to feed the crickets for 2- 3 days with commercial cricket food, flake fish food, oranges and other fruits before feeding them to your frogs.

Springtails – cultures available commercially, or these tiny insects can be gathered below leaf litter, along with small millipedes. These are particularly useful when raising young frogs.

Termites – an absolute favorite, and one of the most valuable food items of all. Collect termites in dead logs. Termites love to eat cardboard – damp pieces placed below a board near a colony will attract hoards (I’ll provide info on a trap you can make in a future article). Escaped termites (other than a queen!) will not establish a colony in your home.

Flour beetle larvae – I was introduced to these by poison frog expert Bob Holland, who had frogs living into their late teens long before zoos here were able to do so. Flour beetles can often be found in old boxes of cereal or dog biscuits, or can be purchased from biological supply houses.

Ants – you’ll need to experiment here, as some species are unpalatable, but it is worth the effort. Keep your eyes open for mating flights, when thousands can be collected. Do not leave large numbers of ants in the terrarium.

Aphids – these tiny insects may be found on plant stems. Clip the stem and place it in the terrarium, or shake the insects over the tank – your frogs’ reactions will leave no doubt as to their appreciation of your efforts!

Wild caught insects – light traps such as the Zoo Med Bug Napper will provide tiny flies, gnats, moths and midges.

“Field Plankton” – this is the term for insects gathered by sweeping tall grass with a net. Of course you will need to exclude large and dangerous insects and spiders. One way to do this is to place the contents of the net in a plastic container perforated with tiny holes, so that only the smallest insects can escape into the terrarium.

Blue poison frogs should be fed every day or two. They have quite large appetites and, in contrast to other frogs, rarely become obese in captivity. Their condition should be monitored closely – thin animals will exhibit protruding hip bones and flat stomachs. This is especially important in group situations, where dominant animals might prevent others from feeding properly.

The food given to growing frogs should be powdered with a vitamin/mineral supplement at every other feeding, or at every feeding if their diet is not varied. Adults do best when supplemented twice weekly.

Captive Longevity
Captive longevity approaches 15 years.

Enrichment
There are a great many techniques that can be used to enrich the lives of your pets. I’ll address several of these in a short note next week.

Breeding
Breeding poison frogs is a fascinating endeavor. These and related species have quite complicated reproductive behaviors, and exhibit a high level of parental care to their eggs and tadpoles. I will address this topic in a future article. Until then, please share your own thoughts and questions. Thanks, Frank.

An article with natural history details and information on the care of blue dart frogs in zoos is posted at:http://www.waza.org/virtualzoo/factsheet.php?id=403-004-002-004&view=Amphibia&main=virtualzoo

The Natural History and Taxonomy of the Blue Poison Frog, Dendrobates azureus (tinctorius)

Dendrobates tinctorius

Overview
The spectacularly colored blue poison frog is now so well established in the pet trade that it seems hard to believe that the animal was not scientifically described until 1969 (by Dutch herpetologist M. Hoogmoed). The care of this highly desirable little frog is well understood, and I will review it in a future article. For now I would like to focus on its natural history and behavior in the wild.

A recent American Museum of Natural History sponsored review of poison frog taxonomy revealed this frog to be a local color morph of the dyeing poison frog, Dendrobates tinctorius, and not a separate species. The scientific name D. azureus is, therefore, no longer recognized by herpetologists. The blue dart frog varies so much in appearance from the dyeing dart frog that many find this information difficult to accept, and so the name D. azureus is still much used. Other quite variable color phases and races of the dyeing poison frog range throughout the lowland forests of French Guiana, Guyana and adjacent areas of Brazil.

Physical Description
The term “electric blue” is often used to describe this frog’s background color, and certainly there is some justification in that. The blue poison frog really must be seen if one is to get a sense of its appearance, as words cannot convey the over-all effect of the startling mix of colors. The body and head are sky-blue spotted with black, while the arms and legs are a brilliant dark blue. Males have wider front foot toe pads than do females, and are a bit thinner in build. Otherwise, the sexes are quite difficult to distinguish. Blue poison frogs average 1.5 to 1.8 inches in length.

Range and Habitat
The blue poison frog has an extremely limited natural range, being known only from the Sipaliwini Savannah on the western slope of the Vier Gebroeders Mountain in south-central Suriname (on the northern coast of South America).

It inhabits fragments of moist forest within a dry savannah (grassland) at approximately 1,150 feet above sea level. This area was most likely covered by trees in the past – as the habitat changed to grassland the frog became isolated those few, tiny patches of forest that persisted. Blue poison frogs live on land in the vicinity of running streams (they do not swim) and occasionally climb trees to heights of 20 feet or so.

Status in the Wild
Despite a great deal of scientific and pet trade interest in this species, its status in the wild has not been well-documented. The species’ continued existence is jeopardized by its tiny natural range and the threat that forest fires from farming activities will destroy what little habitat remains.

The blue poison frog is classified as “Vulnerable” by the IUCN, listed on CITES Appendix II and protected by the government of Suriname. Fortunately, it is frequently bred by hobbyists and in zoos. Inbreeding may, however, be a concern in the future, as new animals have not been legally collected for the pet trade in some time (illegal collecting is thought to occur). Herpetologists from the National Aquarium in Baltimore have received permission to bring new animals into captivity.

Diet
In common with other poison frogs, this species feeds mainly upon ants and termites (those I have kept preferred these to all other foods), but also takes tiny spiders, millipedes, springtails, beetles and other small invertebrates found in leaf litter.

Reproduction
Males call from below fallen leaves and other protected sites on land. In contrast to many frogs, female blue poison frogs actively court the males by stroking the snout and back. Females lay 2-6 eggs in a hollow below leaves, fallen logs or in similar moist, protected locations, after which they are fertilized by the male. The eggs are tended by the male, and sometimes by the female as well. Males soak in water and then lie over the eggs to moisten them, and may tend several clutches at once. The eggs hatch in 14-18 days and the tadpoles are transported to streams on the back of either parent. The tadpoles feed upon algae, decaying plants, Daphnia, mosquito larvae and other small, aquatic invertebrates and each other, and transform into frogs in 70-85 days.

Miscellaneous
The taxonomy of the family to which this species belongs, Dendrobatidae, is quite confusing due to the widely differing appearances of individual frogs of the same species (i.e. the blue and dyeing poison frogs). Also, captive poison frogs of different species, subspecies and populations readily interbreed, raising the possibility that such may occur in the wild as well. There are now considered to be 5 species of frogs within the genus Dendrobates, and 164 species within the family Dendrobatidae.

The blue poison frog and its relatives secrete virulent skin toxins (histrionicotoxins, pumiliotoxins and others) when disturbed. Originally, these toxins were thought to occur naturally within the frogs, in the manner of snake venom. However, tests at the National Aquarium in Baltimore and elsewhere revealed that some captive poison frogs were lacking in skin toxins. However, the same frogs, when released into an indoor “rainforest” at the Aquarium, soon developed the toxins. Subsequent research revealed that these unique chemicals are derived from alkaloids harbored by certain ants and millipedes (and possibly other invertebrates) that the frogs prey upon. Frogs consuming the standard captive diet of fruit flies and crickets soon lost their toxins and were unable to synthesize others.

The skin secretions of 3 poison frog species belonging to the genus Phyllobates were harvested by the Mucushi, Chaco and possibly other people in Columbia, South America for use on hunting darts (contrary to popular belief, frog toxin use in warfare has not been documented). These species, the golden poison frog, P. terribilis, the bi-colored poison frog, P. bicolor, and the Kokoe poison frog, P. aurotaenia utilize secretions, known as batrachotoxins, which differ from those in the skins of Dendrobatid frogs. Batrachotoxins have only been identified in these 3 frogs and, oddly enough, in 2 birds native to New Guinea. Batrachotoxins cause heart failure by suppressing nerve impulses. A single 2 inch long golden poison frog harbors enough of these chemicals to kill 10-20 people.

The skin toxins of the blue poison frog and related species are highly complex and are being studied with a view towards developing medications that may be useful in oncology and infectious disease research and treatment. One compound derived from the secretions of the phantasmal poison frog, Epipedobates tricolor, shows great promise as a pain medication – more effective than morphine, it is both non-addictive and non-sedating.

The use of frog toxins on hunting darts was first reported in the literature in 1823, by British naval captain C. Cochrane. He observed golden poison frogs to be confined and fed by their captors until their skin secretions were needed. The chosen frog was then pierced with a stick in order to induce the secretion of the toxins, which appear as a white froth on the skin. Up to 50 darts could be treated with the secretions from a single frog, and the darts were reported to retain their potency for up to 1 year. A jaguar shot with a dart so treated was said to die within 4-5 minutes, with smaller animals being killed instantly.

There is much more, known and unknown, about this fascinating frog and its relatives. Until next time, please write in with your comments and questions. Thanks, Frank.

An interesting article concerning the complex breeding behaviors of various poison frogs is posted at:
http://animals.jrank.org/pages/148/Poison-Frogs-Dendrobatidae-BEHAVIOR-REPRODUCTION.html

How Reptiles Adjust to Novel Situations – Notes on African Spurred Tortoises, Geochelone sulcata and Aldabra Tortoises G. gigantea

African Spurred Tortoise
Reptiles are often thought of as “unresponsive” by those who are unfamiliar with their ways. Reptile enthusiasts, of course, know better – anyone who has kept a turtle has no doubt been impressed by the speed at which they learn to make associations (especially where food is involved!). Of the turtles, the tortoises seem particularly quick to learn new behaviors.

Aldabra tortoises kept at the Bronx Zoo, to my surprise, adopted a unique strategy to avoid losing their dinners to exhibit mates. At feeding time, each tortoise would lie down on its food tray and slowly edge backwards, eating on the way and so exposing only a tiny bit of its meal to others at any one time!

At a record weight of 240 pounds, African spurred tortoises, the world’s third largest species, seem ill suited as pets. Yet they remain popular, due partly to their engaging ways (please research their needs carefully when deciding upon a pet tortoise – most people are better off with smaller species). Three kept by a friend in a large apartment in NYC would move from room to room throughout the day, following the sun. If a closed door blocked their way, they commenced pounding upon it with their carapaces (upper shells). The racket (and damage to the door) wrought by three frustrated 50 pound tortoises soon “taught” my friend to leave their basking path unimpeded!

I’m quite sure that many of you have amusing tortoise stories – please consider sharing them with myself and other readers. Thank you. Until next time, Frank.

You can get some idea of the rewards and difficulties of life with a giant tortoise at:
http://www.tortoise.org/archives/sulcata1.html

Mate Selection and Sperm Competition in the Painted Dragon, Ctenophorus pictus, and Other Reptiles

Females of many animal species are polyandrous, meaning that they mate with several males. Often, we are learning, the sperm survives for some time inside the female, and competes with the sperm of other males. In this way, only the “fittest” sperm will prevail and fertilize the eggs, assuring vigorous offspring. Females choose mates based on a wide variety of factors, and the criterion used by Australia’s painted dragon lizards turn out to be quite unique.

In contrast to most lizards, male painted dragons have either red or yellow heads, and are chosen by females based on their head color. Research published this week (WollongoGreen Anacondang University) has revealed that female dragons do not choose 1 color over another, but rather seek to mate with 1 male having a red head and 1 with a yellow head. It is theorized that by choosing males of both colors, the female is assuring that she is mating with more than 1 male, and not with the same male twice.

Polyandry among reptiles can result in amazing spectacles – I shall never forget the sight of a huge “breeding ball” – 9 males and 1 female- of green anacondas, Eunectes murinus, on the Venezuelan llanos. In many different animals, sperm can remain alive and able to fertilize eggs for years to come. Queen termites mate once and somehow produce fertilized eggs for up to 20 years after!

Several pet trade reptiles are polyandrous – please share your own observations and questions. Thanks, until next time, Frank.

Further information concerning research with this species at Wollongong University is available at:

http://www.ncbi.nlm.nih.gov/pubmed/16254915

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

Click here to read the first part of this article
Bacteria

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
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.

Parasites
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. Please write to me and share your thoughts and observations. Thanks. Until next time, Frank.

A variety of articles on amphibian and reptile health, written by one of this field’s leading veterinarians, are posted at:http://www.azeah.com/

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