Keeping and Breeding the Mossy Frog
(Theloderma corticale)
By Patrick Nabors

Introduction


One of the most beautiful frogs to come along in years! 
The mountainous forests of northern Vietnam have been out of reach for scientists and researchers for decades, but in the past ten years this area is being explored, and an incredible array of fascinating, and often bizarre, wild life has been found there, much of it new to science. Many of these are reptiles and amphibians. While the subject of this article, Theloderma corticale, or the Vietnamese mossy frog, was officially described in 1903, little was known of its biology and life cycle until recently, when some herpetologists and collectors rediscovered this frog. A combination of wild caught specimens and some captive bred frogs have reached the US in the past few years, and the Mossy frogs striking appearance and ease of care have made them increasingly popular.

General Information

The Mossy frog comes from mountainous areas characterized by limestone outcroppings, cut through by mountain streams. The frogs seem to inhabit the niches in the banks of the streams, as well as other aquatic habitats, including man made reservoirs. The frogs are found at an altitude of about 3000 feet.

Mossy frogs reach an adult size of approximately 2.25 inches to about 3 inches in length. They are almost as wide as they are long when they are in their resting posture, when they are quite flattened, and have a very low profile, which allows them to practically disappear if placed against the right background.

The coloration of the frogs of course aids in their disappearing act, as does the rough texture of the skin, which is unlike that of any other frog that I am aware of. As if the rough peaks and valleys of their skin were not enough, the frogs also sport a colorful appearance, with several shades of green, patches of red, and black. Like most frogs, the Mossy frog is nocturnal. However during the day they will often be found sitting out in the open, counting on their cryptic appearance to keep them concealed. This works very well for them, and it is often a challenge just to find all the frogs in their tank, even though they are sitting out in plain view!

Captive conditions

Mossy frogs are fairly undemanding subjects! They don't have any special lighting requirements, and they seem to do well when kept at temperatures in the low to mid seventies. Temperatures above eighty should be avoided if possible, although spending a couple of hours occasionally at 80—82 doesn't seem to cause a problem. Here at our facility, temperatures sometimes get into the sixties at night, and there doesn't seem to be a problem with this, as you would expect from a frog that comes from a climate that can get cooler during the winter months. In fact I suspect that these frogs will handily deal with temperatures in the forties, but I haven't subjected mine to temperatures that low.

While some keepers have found that moving water is a requirement, we have not provided it here for our frogs, and they seem to do fine without it. However, providing moving water, with a submersible pump and attached filter, would undoubtedly improve the water quality, and more accurately reflect this frogs natural habitat, so a pump and filter should be considered for your Mossy frog setup.

Crickets have been the sole food for our group of Mossy frogs. Every few nights a container of crickets is placed in the tank, and the frogs will eat from this container. Typically we use a plastic “sweater” box, which is floated on the surface of the water. In a smaller tank, or with a smaller group of frogs, the plastic “shoebox” size box would be fine. Before we offer the crickets to the frogs, they are dusted with equal parts Rep-Cal and Herptivite. The next day the cricket container is removed, and any uneaten crickets are discarded. Offering food in this feeding station will prevent crickets from drowning in the water, as well as assuring that the crickets the frogs get have some supplement on them. About four crickets per mossy frog are offered. Mossy frogs seem to have a slower metabolism than some other large frogs, and ours are doing very well on a feeding schedule of every four or five nights.

Mossy frogs are not picky about their lighting, and either background lighting or standard fluorescent lighting is sufficient. We have kept ours at a 12 hour on, 12 hour off photo period year round with good success.

We have kept our group in a tank with about 75% of the lid covered with plastic sheeting, to increase the humidity in the tank. The relative humidity typically runs about 65% to 85%. To achieve the appropriate humidity, I suggest a tank with a lid that has restricted ventilation, and a daily spraying of the tank to keep things wet!

Housing

While the Mossy frog is a pretty good size frog, they are not as jumpy as many frogs, and their primary flight mechanism seems to be to dive into water and try get under something in. For this reason, among others, I suggest that the tank should offer a large water feature, something at least a couple of inches deep, and six to ten inches wide by ten to twenty inches long. A good size tank that is easily available would be a thirty or forty gallon “breeder” style tank, the ones that are 36” long and 18” wide. This will give a respectable amount of room for a group of four to six of the frogs to move about.

Here we are housing our group in a custom built tank that is 48” long by 24” wide, by 24” in height. The floor of the tank is covered by about 3 inches of water. There are several floating pieces of cork bark in the tank, and a long branch that runs from one side of the tank to the other, and goes in and out of the water. An additional feature of the tank is an “island” which is made from a plastic sweater box, filled with gravel and planted with tropical plants. The sweater box has several holes in the bottom, and when placed in the water, the weight of the gravel causes it to sink.


Mossy frogs like to hang out at waters edge.
Another approach might be to use river rocks, 2-3 inches each, to form a land area in one end of the tank. The pump could be hidden in this area. Then fill the tank with water to a depth of about three inches, and float a few pieces of cork bark in the water. This sort of tank has the advantage of being easy to break down and clean periodically.

 

Breeding


A Mossy frog pair in amplexus.
Obviously in order to breed these frogs, individuals of both sexes will be required! Unfortunately, juveniles, which are by far the most commonly available size Mossy frog, are completely unsexable, so your best bet is to get a small group of these frogs to work with, and hope you get both sexes. In most frogs of this sort, best breeding seems to occur when the females have males to choose from, and while I can't say for sure that this is the case with this frog, I would guess that it is. So if you do have the opportunity to obtain sexed animals, I would get a male heavy group.

As for sexing adult frogs, most males are smaller and slimmer than females, but the most reliable indication of the sex of the frogs is the presence of “nuptial” pads on the males. These pads, named for their role in breeding, are used by the male to grip the female during courtship and spawning. These pads can be seen on the adult males, on the inside of front foot, basically on what would be our thumb. The pad is an enlarged area on the thumb, which is usually pink or red.

Nothing special is done to induce our frogs to lay eggs, they are kept under very similar conditions year round, and we do not increase the number of times per day they are misted, (usually twice for about 3 minutes), or the humidity in the tank at any particular point in time

When our mossy frogs are breeding, the can be heard calling, both during the evening hours after the lights have gone out, and in the morning after the lights have come on.

Mossy frogs have a quiet, melodious call, which is very pleasant. Calling is heard from our group most days and evenings, but prior to eggs being seen in the tank,

a female and male can be found locked in amplexus. The male and female may move around the tank for a day or so before actually spawning.

Eggs are laid at or just above the waterline. In our tank the most popular spot for egg laying is on the underside of a branch that runs in and out of the water. The clutches are composed of separate eggs each in their own gel packet, usually placed about a quarter to a half inch apart. The eggs, including the gel packet, are about 3/8ths of an inch across when first laid, but later the gel packet swells considerably as they absorb water. Clutch size is typically between ten and thirty eggs.


These Mossy frog eggs are nearly ready to hatch.
When the eggs are first found, they are removed and placed in a Petri dish for incubation. Each egg is removed from the surface that it is attached to with a pair of tweezers, or scraped off with a flat stiff item like a credit card. The eggs are quite durable. About two teaspoons of water are added to the dish with the eggs, enough to come about half way up the sides of the eggs. The eggs, like many amphibian eggs, have a dark upper part, and a lighter lower part. The upper part is where the egg is attached to what ever it was laid on, and the eggs are removed and placed in the same orientation in which they were laid. About five to seven days later, the gel packet around the egg will have swollen significantly, and the developing tadpole is clearly visible on the egg. After about 15-20 days the tadpoles are fully developed and erupt from the eggs. Fertile eggs have a very high success rate, as do the tadpoles, which are quite large and sturdy.

 

Tadpoles and Froglets

After the tadpoles are about four days old, they are set up in small groups, about six to eight, in plastic storage boxes. We usually start them in a “shoebox” size box, and then move them into the “sweater box” size box after about a month. The tadpoles start out in about two inches of de-chlorinated tap water. A few oak leaves are added to provide some shelter for the tadpoles. The tadpoles are fed dried spirulina and chlorella algae. The algae is sprinkled on the water surface, and allowed to sink to the bottom where it is eaten. Other breeding accounts mention a variety of foods, but we have had good luck with this diet. Partial water changes are made every few days, at which point more food is added.

We have also had good luck raising the tadpoles singly in 16ounce deli-cups, actually development is faster and the emerging frogs are a bit bigger, but the work of keeping up with all the individual tadpoles is a bit much, and we have found it to be a very acceptable compromise, to have the tadpoles take a little longer to develop. Tadpoles that are raised individually take about sixty days to emerge, while tadpoles raised in groups can take four to six months to emerge. Water temperatures are kept in the 70's, although some tadpoles which escaped into the sump of the tank were observed to take eight months or more to emerge. The water temperature in this sump was usually in the low sixties.

The end stage tadpole is quite large, often exceeding three and half inches in total length, with most of this being tail. As the tadpoles get ready to emerge, they begin to get their awesome coloration, and the texture in the skin begins to appear.


Even though this young mossy frog hasn't yet fully absorbed its tail, you can already see much of the frogs color and skin texture.
The young mossy frogs should be offered both water and dry land in their tank. The rearing tank should be pretty simple, we have used the following simple setup with good success here. Depending on how many you are housing, the juvenile Theloderma can be kept in a ten or twenty gallon tank, with a two inch block under one end, so that water will fill one end of the tank, and the other end is dry. Add a couple of pieces of cork bark floating in the water. Keep the juveniles in the mid seventies or below for best results.

Two to three times a week, dump out the water, and clean the tank out. Then wipe the terrarium dry, and add a few dusted crickets of the appropriate size, about as long as the frogs head is wide. Leave them in the tank with the frogs for a couple of hours. After the frogs have eaten, remove any left over crickets, and add fresh water to the tank.

Growth is rapid, and by six months of age the frogs are about two inches long. At this point the frogs are large enough to go into their adult terrarium. Maturity is reached at about one year of age, but could vary by several months depending on things such as feeding frequency.

Prior to getting my frogs, I did some research and uncovered a couple of good reports of breeding this species. Both included using a winter cycling to good effect. This included cooling the frogs somewhat, and changing the photo period to a shorter day time period. When we received our frogs, it was in October, and I thought I would get them settled in, and then if I had not had any breeding after a month or so, I would cycle them. I was pleased to find eggs within a couple of weeks in the setup, and this group of frogs has yet to quit laying eggs. The frogs are quite prolific, and each female is capable of laying a clutch at least once a month.

I am not sure, but I suspect the frogs I received were captive bred in Thailand, so this may account for the ease with which they spawned here, compared to the specimens which previous keepers had been working with, which were most likely wild caught frogs.

Conclusion

The Vietnamese mossy frog is a frog of uncommon beauty, and is quite simple to keep and breed. It is not often that such an awesome animal pops up in the hobby, and I am guessing that more and more people will want to try their hand at keeping these frogs!

 




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