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

The African bullfrog is notorious for its immense appetite and willingness to take on quite formidable prey, including venomous snakes, scorpions and centipedes (please see my article “An Appetite for Cobras” for further details). At breeding time, however, males display a quite unexpected side – that of devoted, even “tender” parents.

Taking on all Foes – Lions Included!
Approaching 9 pounds in weight and 10″ in length, male African bullfrogs are the heaviest, if not longest (that title goes to West Africa’s goliath frog, Conraua goliath) of all Anurans. Bony projections (odontoid structures) that function as teeth line their lower jaws and fights for breeding rights sometimes result in fatalities.

Upon successfully breeding, however, the male African bullfrog turns his pugnacious nature towards defending his numerous eggs and tadpoles, and he is fearless in that task. I have seen footage of one leaping at the faces of African lions that had shown interest in his precious charges (the lions were only about 2 years old, but still not animals to be taken lightly!). Startled by the frog’s complete lack of respect for their size, the lions quickly moved off!

An Anuran Engineer
Perhaps even more surprising, the attentive males will, using the hardened tubercles on their hind feet, dig channels in the earth to lead tadpoles from drying to water-filled pools (or, perhaps, to direct water into the natal pool).

Parent Turned Predator
Once the tadpoles transform into small frogs, all bets are off and the male ravenously consumes all that he can catch. Other African bullfrogs may constitute the majority of the diet of newly transformed animals as well…breeding pools dry quickly in most habitats, and the frogs must gorge themselves before retreating underground for a dormancy period that may approach 1 year in length.

There is, however, evidence of kin recognition in African bullfrogs…so relatives may be spared (or at least only eaten as a last resort!), as is the case for the tiger salamander, Ambystoma tigrinum. In that species, cannibalistic larvae have been shown to preferentially prey upon non-related animals.

I’ll cover the captive husbandry of this unique heavyweight in the future.

You can read more about this frog’s natural history at:
http://research.amnh.org/herpetology/amphibia/index.php

The success that hobbyists have had in establishing breeding populations of so many species of poison frogs is truly astonishing, and has served a greater purpose in removing the financial incentive to collect them from the wild.

Unfortunately, the extraordinary parental care supplied by many poison frogs is difficult to observe in captivity, and the most effective way of rearing the tadpoles is to remove them from their parents’ terrarium. I was most fortunate to have had the opportunity to observe the breeding behavior of wild strawberry poison frogs in Tortuguero, Costa Rica, and in a large zoo exhibit.

Finding and Feeding the Tadpoles
Strawberry poison frog tadpoles, which are moved by the female frog to individual water-filled bromeliad stems, exhibit what has been termed “begging behavior” when their mother visits their pools. When the female lowers her vent into the water, the tadpole moves against her, stiffens, and vibrates. This stimulates the female to release 1-5 unfertilized eggs, which comprise the tadpole’s sole diet.

She visits and feeds each of her offspring, every other day or so, for the 43-52 days that they remain in the tadpole stage…no wonder these tiny moms eat so much! When one considers the complexity of the frog’s rainforest environment, especially as compared to the size of the frog, the female’s ability to locate each tadpole borders on the unbelievable.

Additional Behaviors
Outstanding herpetologist Elke Zimmermann (in “Breeding Terrarium Animals, 1986. TFH: Neptune City, NJ) has even observed females to dip their heads into bromeliad pools before laying, and notes that disturbances from other than the mother frog sends the tadpole into retreat. Field research in Panama indicates that female strawberry poison frogs consistently avoid feeding other than their own progeny.

I was able to observe parental care only in huge exhibits and the wild, but please write in if you would like to try at home…it’s well worth the effort.

We now know that Chirixalus eiffingeri, a treefrog endemic to Taiwan, also communicates with and feeds its tadpoles. The abstract of an article documenting this behavior is posted at:
http://www.ingentaconnect.com/content/brill/beh/2000/00000137/00000001/art00009?crawler=true

Socially Influenced Mating behavior
Ever wonder how a male frog might draw the attention of a female when he is calling amid hundreds of others? Research published in the August, 2008 “Journal of Comparative Psychology” has revealed that gray treefrogs vary their calls in response to social situations. When alone or in small groups, males utilize the species’ usual call. However, when trying to attract a mate amid large groups, males will vary the rhythm of their calls, in order to stand out from the crowd.

The Only Ultrasonic-Sensitive Frog
Concave-eared torrent frogs have, as one might guess from their name, recessed eardrums. Biologists looking into why this species’ eardrums are not level with the skin, as in most other frogs, discovered that these natives of central China emit and hear ultrasonic mating calls. This is likely because noise from the rushing streams along which they dwell would drown out calls emitted in the lower sound ranges (which are used by most frogs). Until now, only bats, whales and certain insects were thought to utilize ultrasonic calls.

Unusual Ears
And why the recessed eardrums? As stated in an article published in the May, 2008 issue of “Nature”, the torrent frogs eardrums are only 1/30th as thick as the eardrums of other frogs (which are, I imagine, quite thin themselves!) – an adaptation to allow the detection of ultrasonic sound. Their recessed location is thought to confer some protection against injury.

You can learn more about the concave-eared torrent frog’s natural history at:
http://amphibiaweb.org/cgi/amphib_query?where-genus=Odorrana&where-species=tormota

Image referenced from Wikipedia, http://en.wikipedia.org/wiki/Image:Hyla_versicolor.jpg, and taken by LA Dawson

Today I would like to offer a look at how I set up a terrarium for animals in my own collection. After decades keeping animals privately and professionally, my techniques have become a fusion of tried and true methods and ideas that I have either worked out or (often!) stumbled across. Of primary importance has been the writings and personal advice of many kind and dedicated people.

Wonderful but Neglected Terrarium Pets
I’ve never quite understood why barking and gray treefrogs have remained largely ignored by herptoculturists. Both are beautifully patterned – the gray frog subtly, the barker often quite brilliantly – and almost always make themselves right at home in captivity. Wild caught adults of either species have hand-fed for me as soon as 1 week after capture, and a gray treefrog that I have now approaches the glass when I enter the room, in a much more “turtle” than “frog-like fashion”. At nearly 3 inches in length (and appearing larger due to its stocky frame), the barker is the USA’s largest native treefrog, exceeded only slightly in size by the introduced Cuban treefrog (Osteopilus septentrionalis).

Setting Up a Battery Jar Terrarium
I currently keep 1 barking and 1 gray treefrog in a battery jar terrarium of about 10 gallon capacity. I favor battery jars for the simple reason that they were always mentioned in the naturalist/pet-keeping books of yesteryear. As a child, I had no idea what a battery jar was, but imagined it to be a fabulously exotic item, the possession of which would confer instant “professional animal-keeper” status upon me.

In reality, battery jars are thick-walled, usually cylindrical glass containers available from biological/laboratory supply houses. Their vertical orientation serves arboreal frogs well, but a 20 gallon “extra-hi” aquarium or larger plastic terrarium is also perfectly suitable.

My battery jar was modified for use as a terrarium by Bob Holland, a friend who was well-known in the 60’s and 70’s for his success in keeping – years ahead of most public collections – poison frogs, banded tree snails, woodland salamanders, mosses, ferns and a host of other delicate organisms.

Bob used aquarium silicone and a piece of glass to create a small pool and to attach a hollow piece of lava rock about ½ way up one side of the terrarium. The lava rock functions as a planter, and the area below as secure shelter…the treefrogs rarely use it, but in earlier times it was favored by a marbled salamander (Ambystoma opacum).

My skillful friend cut a ventilation panel into the terrarium’s glass top, a task I would not attempt. Commercial glass cutters can do this for you if you are as “tool-challenged” as I, after which you can silicone a piece of fine screening in place.

The substrate is Eco earth loose coconut with a bit of sphagnum moss mixed in. A layer of aquarium gravel and activated carbon, situated below the substrate, assists in drainage and ammonia absorption. I use live, locally collected moss on top of the substrate – you’ll need to experiment with the moss species, but many do well with moderate lighting and daily misting. Compressed frog moss works well to fill in dark corners, or as a substrate for the entire tank if you prefer.

Live Plants, Light and Decorations
I chose the live plants for this terrarium based upon their serviceability as frog perches and modest light requirements. The aptly-named cast iron plant (Aspidistra elatior) is nearly indestructible, and is often used as a perching site. The Chinese evergreen (Aglaonema modesta), snake plant (Sansiveria spp., not pictured) and earth star (Cryptanthus spp.) are equally hardy. Earth stars are a favorite of tarantula-keepers, as they get by on very little light (they turn brown at such times, but return to red when moved to a brighter location).

A Reptisun 2.0 florescent bulb provides sufficient light for the plants without exposing the frogs to harmful levels of UVB – most amphibians have UVB “filters” in their skin, and actively avoid the sun.

A Caution Concerning Light
I have noticed corneal opacities in green and gray treefrogs that consistently perch directly below even low-level UVB output bulbs. To be on the safe side, keep track of your frogs’ perching habits. Most tend to choose the same spot day after day, and it is usually an easy matter to fashion a shield (i.e. an artificial plant) between the frog and the bulb.

A few attractively-weathered pieces of driftwood provide additional climbing surfaces. Exo terra terrarium plants are extremely life-like, more so when integrated among living plants. I find them especially useful in creating exhibits in zoos and museums, where the plant species used must match those found in the subject animal’s habitat, or where light levels limit the use of live plants.

Heat
One drawback of a battery jar terrarium is the relatively small area that can be vented. In the summer, temperatures within may become too warm for most amphibians, if even a florescent light is used. The aforementioned plants will usually survive on room light alone for a few months – to be safe, I set the terrarium light to go on for 2-3 hours during the cool of morning.

Plants as Waste Managers
I always fear downplaying the importance of regular cleaning, and it is not my intention to do that here. However, well-planted terrariums that are lightly stocked with animals are a delight to maintain.

The key is to have enough plants with vigorous root systems, live moss if possible and to find the right balance of plants and animals. The tank pictured here would actually be more easily maintained with just 2 gray treefrogs, or a single barking treefrog, as opposed to 1 of each, but I am familiar with its capabilities, and monitor it carefully. This terrarium has been up and running, with only two major substrate changes (one after housing a sick animal), for nearly 12 years.

Help From Snails and Sowbugs
In addition to the plants, I am assisted in tank maintenance by a thriving colony of land snails and sowbugs (Check Out: Terrestrial Isopods as Food for Captive Reptiles and Amphibians ). Both avidly consume the frogs’ waste products and decaying plant material, and neither requires additional food. The sowbugs provide an alternative food source for the frogs as well. I spot clean when necessary, occasionally replace the top inch of substrate, and change the pool’s water by wicking it out with paper towels. A layer of activated carbon below the substrate (an old trick now largely forgotten) helps to absorb nitrogenous wastes.

Feeding Native Treefrogs
Wild Caught Insects
My gray treefrog hatched in captivity, and the barker acts as though it did – both feed avidly from the hand. This allows me to more easily provide a varied diet, as they will take canned insects such as caterpillars and grasshoppers. From spring through fall, I feed the frogs exclusively upon insects that I trap with a Zoo Med Bug Napper or collect around my outdoor yard light. An insect or 2 each day or so suffices, and the dietary variety is key to good health (Check Out: Providing a Balanced Diet to Reptiles and Amphibians).

This is just a thought, but I believe it cannot hurt to attempt to provide arboreal and flying insects to tree frogs – especially so if you live within the range of the frogs that you keep. Mine favor moths, tree crickets, small katydids, caterpillars, beetles, harvestman (“daddy longlegs”) and flies. I avoid spiders, fireflies, ladybugs and brightly colored species, due to possible toxicity problems, and do not collect for a week or so after the area has been sprayed to control West Nile virus ( I believe the plane-sprayed insecticides kill far more cicadas than mosquitoes, but I digress…).

Commercially Available Insects
During the winter, temperatures in the terrarium average 62-65 F, the light cycle is reduced to 8 hours, and the frogs slow down. A once-weekly feeding of crickets (use only small ones for gray treefrogs), mealworm beetles, waxworms and earthworms holds them until tastier meals return (most treefrogs refuse earthworms, but some individuals will accept them).

I powder feeder insects with a vitamin/mineral supplement during the winter only – I’ve found such is unnecessary in summer, when wild caught insects dominate the diet.

The frogs and terrarium are sprayed once or twice daily with de-chlorinated water (both species use the pool as well).

There are 2 nearly identical species of gray treefrog in the Eastern USA. You can learn how to distinguish them, and a bit about the National Wildlife Federation’s laudable Frogwatch USA Program, at:
http://www.nwf.org/frogwatchusa/content_amphibianprofile.cfm

Harvard biologist David Blachurn knew he was onto something unusual when a benign-looking frog he was examining in Cameroon, West Africa kicked out and left him with a bleeding cut.  Unusual indeed – an article  (23 August 2008) in Biology Letters describes the hidden claws of Perret’s night frog as the only vertebrate claws known to break through the skin in order to become functional.  Some, or possibly all, of the other 10 frogs within the genus Astylosternus are also equipped with skin-covered claws on their toes (the fingers are clawless).

The frog’s sharp, curved claw is actually the last bone of the toe, and pierces the toe’s skin when a specific tendon is flexed.  It is assumed that the claw retracts after use and the skin heals, but further study is needed.  Other amphibians that experience “self-inflicted” wounds include the Surinam toads, Pipa spp., whose young push through the skin of the female’s back when ready to swim off on their own and the ribbed newt, Pleurodeles waltl.  The ribs of this newt pierce the skin of the back, carrying toxins with them, when the animal is threatened.

Despite the massive trauma caused by the emergence of 80+ fully formed little frogs, the skin of breeding Surinam toads (P. pipa) under my care appeared well-healed within 24 hours.  I’m sure there are some compounds that may be of medical use to people hidden in the body chemistry of this and other amphibian species.

Of course, people living within the habitat of Perret’s night frog have long known of its odd defense and even utilize specially-constructed spears when hunting it, to avoid being injured.

The only other frogs known to have claws are members of the family Pipidae – the various African clawed and dwarf African clawed frogs.  I have observed both putting their claws, which are always exposed, to interesting uses (more to come in future articles).

You can read more about this frog and related species at:
http://research.amnh.org/herpetology/amphibia/references.php?id=1191