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

The story sparked memories of large snapping turtles I have known, and once again brought to mind how spectacular these relatively common creatures are. We tend to take them for granted here, but they make quite an impression to the uninitiated – hatchling snapping turtles are all the rage in the pet trade in Japan, being described in the media as “tiny dinosaurs” (not far off, in my opinion!).

Until this month’s catch, the largest wild-caught snapper on record was a 76 pound animal (the carapace measured 22 inches) taken from a deep lake in the northeastern USA. The vast majority of very large snapping turtles come from the northern parts of their range (the same holds true for their gigantic cousin, the alligator snapping turtle, Macroclemmys temmincki). As an indication of just how rare such creatures are, consider the following – a review of commercial turtle fisherman’s records show that of 84,000 adult turtles reported, only 160 topped 50 pounds in weight. Of these, only 4 weighed 60 pounds or more. These largest individuals were all males – the heaviest female known tipped the scales at 44 pounds.

Relatively small ponds on Long Island, NY have produced some giants – two that I worked with weighed 54 and 63 pounds when captured. The heavier of these, now a massive 80 pounder, is on exhibit at the Cold Spring Harbor Fish Hatchery (http://www.cshfha.org/).

Of the many large snapping turtles that I have encountered in the wild and in zoos, two in particular stand out (a “small” 15 pound white snapper from NJ is also memorable). Both were found wandering on land (highly unusual) near the Bronx River, in the heart of the Bronx, NY, and showed evidence of recent battles with (most likely) even larger males. The first was delivered to a friend who does animal rehabilitation from his facility in NYC. In order to check the turtle for injuries, we put him on the sidewalk and commenced to hose him off. As the turtle lumbered down East 4th Street, I was, as is usual in such situations, treated to interesting observations of my fellow New Yorkers – some gathered and traded stories while others walked briskly around it as though the 45 pound monster were no more than an upturned garbage can barring their progress!

The second turtle weighed 49 pounds, but was quite emaciated due, I believe, to a severely injured lower jaw that had healed but limited his ability to feed. I installed this fellow in a large outdoor pond near the Bronx Zoo’s reptile house. He soon learned to respond to the sound of my palm striking the water, and would gingerly take a trout (yes, he was spoiled!) from my hand. As they say “Don’t try this at home!” – snappers, even long-term captives, have notoriously well-developed striking abilities, and can cause severe damage injuries (this animal was prevented from doing so by his damaged jaw).

I have worked with most of the giants of the turtle world – leatherbacks, Galapagos and Aldabra tortoises, giant Asian soft-shells and alligator snapping turtles – and will write about them from time to time. For now I’ll pass along some more information about snapping turtles in the wild, and address their care in captivity in Part II of this article.

RANGE
Most of southern and eastern Canada and the United States, east of the Rocky Mountains; subspecies range from Mexico to Ecuador. Widely introduced – California, Nevada and other states in west USA, Japan.

HABITAT
Shallow streams, swamps and ponds to deep lakes and rivers; ponds in city parks and on farms. Some populations inhabit brackish water (tidal rivers and marshes) and have evolved a means of excreting excess salt (Note: I live near a population of these remarkable “salt water snappers” and will report back on them in the future). Rarely leaves the water except to lay eggs; often basks while floating at the surface.

STATUS IN THE WILD
Often the most common turtle within its range and still to be found in quite large cities, yet threatened by collection for the food trade in some areas. In NYC, is relatively common in Central Park, the Bronx River and most other sizable bodies of water; widely farmed. Introduced populations severely impact native turtles and other wildlife.

PHYSICAL CHARACTERISTICS
Massive head, powerful jaws and a long neck. The dark carapace (upper shell) is keeled and serrated at the rear edge. The plastron (lower shell) is quite small. The tail is thick, as long as the carapace, and topped with ridges.

LONGEVITY
To 40 or more years in captivity and to at least 24 years in the wild, but potentially much longer.
REPRODUCTION
In my experience, most females in NYC and the immediate environs lay their eggs on rainy nights in early June. I am always rewarded by the sight of nesting females on such nights and during the following mornings. If you have a chance to visit nesting sites during the breeding season, please do so. You will not be disappointed – egg-laying is fairly well-synchronized in many areas, resulting in a spectacular emergence of females where populations are large.

Mating occurs throughout the spring, summer and fall. Females lay 25-85 eggs, 1-1/8 inches in diameter, in a self-dug hole. Nesting sites are generally in open locations. Females often choose newly dug earth, i.e. dirt piles at construction sites (how they unerringly locate such piles, I do not know – but it is a quite definite choice in my experience).

Incubation takes 9-18 weeks, depending upon weather conditions. In the northeast, hatchlings may over-winter in the nest and emerge in the spring. Females can retain sperm and lay fertile eggs for years after a single mating.

The young, jet black in color, forage for insects, worms and carrion in shallow water, and often remain buried beneath the mud with only the eyes and nostrils exposed (as do adults). Hatchlings are preyed upon by large fish, bull frogs, wading birds and other turtles.

DIET
Nearly any animal within their habitat – fish, frogs, smaller turtles, snakes, insects, snails, crayfish, carrion, muskrats and other semi-aquatic mammals; also take crabs, mussels and clams in tidal streams. A 30 pound individual in a pond at the Bronx Zoo once killed an adult mute swan, and I know of a 10 pound turtle that tried to drag a full grown Canada goose below the water’s surface! Some vegetation is taken as well. Often caught on fishing lines.

Notes concerning nesting snapping turtles (as well as general observations on other turtles) are posted at:http://www.fmap.ca/ramweb/papers-total/James_2004.pdf

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

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!

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