That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

While working in a large tropical bird exhibit at the Bronx Zoo some years back, I was startled to come across tiny frogs hidden among the leaf litter.  I was able to identify them as Greenhouse frogs, Eleutherodactylus planirostris (an apt name, it turns out).  These 1.4 inch-long Cuban natives have been transported around the world, hidden among plants and soil.  Their eggs are laid on land, and the tadpole stage is passed within the egg, so the frogs readily establish themselves in greenhouses and other warm, humid habitats.  It always pays to (discretely) poke around in walk-through zoo exhibits and such places – you never know.

The greenhouse frog belongs to the family Eleutherodactylidea, which contains over 800 species.  Recent research at Pennsylvania State University revealed that all types currently found in Mexico, Central America and the Caribbean arrived there by rafting on vegetation over the open seas from South America, rather than across an ancient land bridge, as was previously assumed.  Apparently, individuals of a single species landed in Mexico, and others (again, 1 species) in Central America, and then each evolved into the large number of species found in these places today.

Another world traveler, the Flowerpot snake (or Brahminy blind snake), Ramphotphlops braminus, also utilizes a unique reproductive strategy to establish new populations in far-flung habitats.  All individuals of this species are female and reproduce via parthenogenesis, so only 1 animal is needed to start a colony.  I’ve had the good fortune of running into this odd creature, as well as “banana” spiders, rattlesnakes and others, in unexpected surroundings – more on that next time.

An informative article on this frog’s history in Florida, along with a photo, is posted at:

http://nis.gsmfc.org/nis_factsheet.php?toc_id=205

Poison frogs respond quickly to novel situations and are among the best amphibian candidates for enrichment experiments. I enjoy watching them “figure out” new things. One technique I use is to place crickets into a container perforated with tiny holes – the frogs soon learn to associate the container with food, and will gather about it, watching the holes for escaping insects. On non-feeding days, you may still notice that the frogs will pause occasionally to peer at the feeder, apparently in anticipation of a meal.

Establishing a colony of springtails (tiny, wingless insects that may be collected below leaf litter) in the terrarium’s substrate will also provide your frogs with “naturalistic” hunting opportunities. Springtails will thrive on decaying moss and the frogs’ waste products, and usually do quite well and provide valuable nutrients to your pets (springtails can also be given a bit of tropical fish flakes on occasion). It is great fun to watch poison frogs scrutinize every inch of the terrarium and to stalk their prey, and they surely benefit from the increased activity levels.

Information about behavioral enrichment for reptiles and amphibians at the National Zoo is posted at:
http://nationalzoo.si.edu/Animals/ReptilesAmphibians/enrichment/

As you may know, the African clawed frog is entirely aquatic but may travel overland in search of water, but only when forced to do so – when its habitat dries out or poison is introduced to its pond. Many years ago I kept an adult pair that would lie out on a rock which protruded above the water, directly under an incandescent bulb. This only occurred in winter, when the water temperature in their tank averaged 66 F, so I thought they might be seeking warmth. However, others I’ve kept at that temperature have not left the water, despite being provided with a basking light as well.

The second observation involves a female clawed frog that laid eggs in absence of a male. That in itself is unusual, as most frogs utilize amplexus (the male grasps the female just behind the front legs or, in Xenopus, just above the rear legs) to induce egg laying. Odder still, however, was the fact that a male placed in the tank with the eggs (and without the female) on the following day fertilized the eggs. He was in breeding condition, as evidenced by the rough “nuptial pads” along his forearms, and perhaps was responding to pheromones or scents in the water, but still should have (according to me, not him, it seems!) required a female to stimulate sperm release. I have spoken with a number of herpetologists about this, and none can recall a similar incident.

Further information on this frog’s mating behavior and ability to travel overland is available at:
http://animaldiversity.ummz.umich.edu/site/accounts/information/Xenopus_laevis.html

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.

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

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.

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