Captive Propagation and Tadpole Husbandry
Mike Pingleton
cage measures 28" x 28" x 60"
rain chamber
amplexing pair
foam nest. note the unfertilized (white) eggs.
dissolving the nest
day-old taddies
foam nest constructed in water tub
same nest, several days later
Asian Foam-Nesting Frogs (Polypedates leucomystax) are a hardy species that do well in captivity. They are relatively easy to raise and to breed. Polypedates leucomystax (Gravenhorst, 1829) are in family Rhacophoridae, and were formerly included in the genus Rhacophorus. They are also known as Golden Treefrogs or Whitelipped Treefrogs. They are a robust and hardy species, with a very wide range in Asia. They are imported regularly and are relatively inexpensive.
In 1999 I purchased and received 40 tadpoles of a species of African frog, Leptopelis. Raising the tadpoles to maturity revealed that a mistake had been made, and what I had was actually P. leucomystax. I was intrigued by the fact that I had raised all forty tadpoles without losing a single one, and decided to go ahead and work with this species as a breeding project.
Two years later I had a nice group of robust, adult frogs. I retained two dozen of the original 40, and these were housed in a large, tall cage suitable for an arboreal species. The sex ratio was about even. The frogs were primarily fed crickets, with small numbers of juvenile hissing roaches. The species is markedly sexually dimorphic in size; females are broader and reach four inches in length, while the more slender males top out around two inches.
Rhacophorids are unique in their foam-nesting strategy, which is tied to the rainy season. With the onset of the rains, amplexus takes place, but before any eggs are laid, the female secretes a sticky substance that she then whips into a foam using her hind legs. Often this is accomplished with a male clinging to her back. Once the foam is in place, the female releases her eggs and the male fertilizes them; the eggs fall into the middle of the mass of foam. In the wild, the nest is usually constructed in vegetation over water. The outside of the foam nest dry and harden into a crust, while the eggs inside remain moist. The eggs develop and hatch, and subsequent rains dissolve the nest, releasing the tiny tadpoles into the water below. This is thought to be a survival strategy, allowing the eggs to hatch and develop in a place secure from predators.
Breeding Efforts
Summer was approaching and it was time to get ready for breeding; the males were already beginning to call at night. I decided to construct a separate rain chamber, using a cheap plastic 'slop sink' for a base, and adding a framework of aluminum window screen stock wrapped with vinyl mesh. To make the rain apparatus I used a small pond pump. and to make raindrops I made a diffuser from a plastic shoebox lid, drilling it full of holes. Plants and plastic shoebox lids were added to provide a surface for attaching nests. A half dozen frogs of each sex were added to the chamber, and allowed to acclimate for a week or so.
Many species of frogs will respond to the low barometric pressure that accompanies a thunderstorm. I watched the local weather for one, and was ready for the one that came through one afternoon. I wrapped the rain chamber with a layer of clear plastic to hold in the humidity, added several gallons of aged and treated water, and turned on the pump as the sun went down. As luck would have it, a line of storms passed through that night as well. Within a short tie period most of the females had a smaller male frog clinging to their back. I stayed up as late as I could, hoping to see nest construction, but gave up around 2 AM and went to bed, shutting off the pump for the night.
In the morning I checked the chamber and found a single foam nest, secreted to the back of a shoebox lid. The interior of the nest is shaped somewhat like a flask - I could look down into the narrow neck and see masses of eggs. I left the nest alone for three days and during that time, two more foam nests were made in the rain chamber, although I had not turned the rain pump back on.
On the third day I dissolved the first nest, still attached to the plastic shoebox top. By this time the outside of the nest had dried and crusted over. Positioning it over a plastic 'catch tub', I slowly sprinkled the nest with a plant watering can; I wanted to mimic rainfall to watch the results. The dry exterior began to melt and sag, and water filled up the interior; after a few minutes, a hole developed at the bottom of the nest, and foam, tadpoles and water dribbled from it.
Three days had been enough for the eggs to hatch, and for the tadpoles to show clear characteristics of eyes and mouthparts. There were close to a hundred tadpoles that emerged from the nest, and perhaps several dozen unfertilized eggs left in the foam mass. The liquid in the catch tub was now a slimy, mucous solution through which the young tadpoles wriggled. Using a plastic turkey baster (the frog breeder's favorite tool) I transferred the tadpoles into their rearing tubs. I made sure there were identical water temperatures in the catch tub and rearing tubs - tadpoles, especially very young ones, are very sensitive to shock from differences in water temperature, and I didn't want to stress them any more than I had to.
I did not wait three days to dissolve the other two nests, since I had a trip out of town coming up. I waited a day and a half this time, and got quite a surprise. The eggs had apparently just hatched, and all of the tadpoles were white! Their eyespots were mere smudges, and the yolk sacs were larger than the tadpoles, which could not move more than an occasional wriggle. After a couple days, these weird looking white wrigglers had acquired a more normal appearance and color, and their yolk sacs had diminished enough for them to move about.
I was quite pleased at having immediate success with my breeding efforts; using the rain chamber and timing it with the rains had been effective. I was in for quite a surprise later that summer, when more nests were created in the water tub in the frog's normal vivaria. These eggs, as with the first batch, were laid after a rainstorm passed through, even though I did not provide any additional moisture. Apparently a low pressure front is enough to stimulate these frogs to breed, and in subsequent years this was repeated.