Andean Marsupial Treefrog page

GENERAL INFORMATION AND RECOMMENDATIONS FOR KEEPING THE ANDEAN MARSUPIAL TREEFROG

The Andean marsupial treefrog is usually missing from the majority of amphibian collections, although these frogs are both hardy and fascinating captives. The uniqueness of the reproductive mode of Gastrotheca riobambae is a fascinating aspect of this frog and makes these species an ideal animal for research, amphibiaculture and education. These species of marsupial frog do not produce and lay clutches of eggs like most frogs, but has its own method of reproduction. The male frog fertilizes the eggs externally and then places them in a pouch on the back of the female frog. The female carries the eggs until they reach tadpole stage. She then deposits them in a pool.

One reason why this frog is not usually available is that it is infrequently collected in its native habitat. But the popularity and enjoyment of this species probably will grow with the availability of captive-bred specimens.

There are some additional features of Gastrotheca riobambae that makes also an ideal animal as a pet. For example: it is a polychromatic species that have a variety of color phases; the call of the male is unique and sounds as a wraaaack-ack-ack. As well, Gastrotheca riobambae adapts well to terraria; it is hardy, adjusts well to captivity and has strong, healthy young marsupial tree frogs. Adults and tadpoles are easy to feed from inexpensive commercial sources.

Egg-brooding and Marsupial Frogs

In the rainforests and mountains of Central and South America live nearly 65 species of tree frogs that have an unusual mode of reproduction. Their eggs develop not in the water but on the mother’s back, often inside a special pouch. Certain features of this unique mode of reproduction recall pregnancy in mammals and the eggs and embryos of birds; others are unique. The embryos protected on the mother’s back can develop at a leisurely pace. In many cases the young emerge as fully formed froglets, in others as advanced tadpoles. In the latter case, tadpoles complete their development in water.

These frogs evolved at about 40-80 millions years, when an ancestral lineage diverged in at least five groups of egg-brooding frogs included in the genera: Hemiphractus, Stefania, Cryptobathrachus, Flectonotus, and Gastrotheca.

Among these genera, the tree former contain species which lack a pouch and their eggs develop on their mother’s back; whereas species in the two latter genera have a pouch.

Gastrotheca contains 45 species which range from Panama to Argentina. Most species occur in the Andes.

This species is endemic from the western slopes of the Andes Mtns. It inhabits paramo habitats and interandean valleys, where this species is widely distributed from the Riobamba basin (south of Chimborazo volcano) to Ibarra in the north. In these basins and paramos, it occurs between 1590 and 3220 meters over sea level.

Individuals of these marsupial frog occur in pristine habitats; but, sometimes they are also found in modified environments which hold remains of natural vegetation in the proximity’s of cities and towns.

Gastrotheca riobambae is a crepuscular and nocturnal species; however, under captive conditions it may be active also during day. Females of this species have a pouch where they incubate eggs until tadpoles emerge from the pouch and they are deposited in water.

During courtship the male calls to attract a female. If a gravid female is attracted to him, he climbs onto the back of the female and performs a nuptial amplexus. As the eggs emerge from the female’s cloaca, the male catches the eggs with his feet and maneuvers them into the pouch. The male opens the pouch with his feet and introduces them to the pouch while he fertilizes them.

A female may incubate an average of 130 eggs. Development in the pouch lasts between 60 and 120 days. Then the female deposits the emerging tadpoles in the water. Free-living tadpoles develop and metamorphose in the water in about two-three months. Froglets emerge from water and males begin to call two months latter. Frogs are ready to mate at about seven months.

Adult females reach 2 and a half (6,5 cm) inches and adult males 2 inches (5 cm) in length. In general, there are two color phases: brown and green. There are also individuals bearing mixtures of these two phases. Color of the juveniles may change from brown to green while they grow up. There are individuals with plain colors, and others bearing longitudinal dorsal stripes.

Both males and females have expanded digital discs on their fingers and toes. These adhesive discs help the frogs to climb and adhere to vertical surfaces. Sexual dimorphic characters allow the recognition of males and females. Males have a gular sac that is inflated when they are calling. Females have a pouch on its back. The female tadpole "pouch" is clearly visible on the lower aspect of her back. This appears as a relatively large, horizontal slit with upturned corners. When females are carrying fertilized eggs on their pouch, swelling becomes visible on the back and this swelling continues to increase over time. As swelling increases, noticeable lumps began to appear beneath the skin of the back. Tadpoles are gray and when metamorphosis is completed the froglets are about an inch (2-3) cm length.

The terrarium can be kept at ambient room temperature 72 to 75 degrees Fahrenheit (22 to 24 degrees Celsius), day and night. A 2.5-gallon aquarium can be used to accommodate adult pairs. Sphagnum moss can be used as a substrate. A water pot is necessary for the frogs to moist themselves and eventually for laying tadpoles. Also, branches provide an arboreal environment where the frogs may climb. Shelter can be provided by a bromeliad, the half of a coconut, cork barks pieces etc. Terrarium can be furnished with small, artificial or natural plants of various types. This results in a "full"-looking cage that provides multiple opportunities for hiding. However, for the frogs to be visible during day you can simplify the furnishing of the terrarium. Frogs basic need is water for moisture. UVB light can be added for 12 hours a day. Humidity can be kept at 60 to 65 percent. The level of humidity can be provided by moderate misting or by the use humidifiers running 24 hours a day.

Adults are fed with large crickets; also they eat earthworms, wax-worm larvae, or recently born mice. Prey items can be coated with vitamin powder once a week and calcium twice a week.

The tadpoles, when deposited, have bodies that resemble split peas, both in size and shape. Tadpoles feed on a wide range of commercial fish flakes, cat and dog food, cooked lettuce, taraxacum, etc.

The tadpoles can be fed rather heavily by the standards of most frog breeders. They can be given a moderate amounting of food four to six times a day as long as tadpoles eagerly eat each time food is offered.

Tadpoles can be kept in tanks with 3 gallons of water (20-30 tadpoles), and can be kept communally. Aged water can be used for the tank. A filter pump can be set up help to oxygenate the water. The power setting on the pump can be set to low. Water temperature can be kept at approximately 72 to 75 degrees Fahrenheit (22 to 24 degrees Celsius).

Froglets will end metamorphosis at about two-three months after released in water. They will eat until approximately two days after the tail is absorbed. At this point, they will begin to feed on dusted crickets.

Most species of marsupial frogs are endangered because of environmental degradation, destruction of habitats, etc.

Some species may be declining or going extinct because of catastrophic declines of frog populations occurring worldwide (mostly in the highlands) due to still unknown reasons. Scientists are trying to reveal this enigmatic extinction.

Except for Gastrotheca riobambae and Gastrotheca peruana, few species of marsupial frogs are being breed under captive conditions and most are rare and poorly known animals.

Auber-Thomay, M. and F. Letellier. 1986. Observations sur le développement de la rainette marsupiale, Gastrotheca riobambae (Hylidés). Revue Francaise de Aquariologie 13(3): 79–86.

Del Pino, E. M., and R. P. Elinson. 1983. A novel development pattern for frogs: gastrulation produces an embrionic disk. Nature 306(5943):589–591.

Del Pino, E. M., M. L. Galarza, C. M. de Albuja, and A. A. Humphries, Jr. 1975. The maternal pouch and development in the marsupial frog Gastrotheca riobambae (Fowler). Biol. Bull., 149:480–491.

Duellman, W. E. 1974. A systematic review of the marsupial frogs (Hylidae: Gastrotheca) of the Andes of Ecuador. Occasional Papers of the Museum of Natural History, The University of Kansas, Lawrence, Kansas 22:1–27.

Duellman, W. E., and T. H. Fritts. 1972. A taxonomic review of the southern andean marsupial frogs (Hylidae: Gastrotheca). Occasional Papers of the Museum of Natural History, The University of Kansas, Lawrence, Kansas 9:1–37.

Duellman, W. E., and D. M. Hillis. 1987. Marsupial frogs (Hylidae: Gastrotheca) of the Ecuadorian Andes: Resolution of taxonomic problems and phylogenetic relationships. Herpetologica 43(2):141–173.

Duellman, W. E., and S. J. Maness. 1980. The reproductive behavior of some hylid marsupial frogs. Journal of Herpetology 14:213–222.

McCready, A. M. 1996–1997. Husbandry and propagation experiences with Gastrotheca peruana. Bulletin of the International Hylid Society 1(4):5–16.

Q. Where and how do the frogs exit the females back?

A. Tadpoles in Stage 25 of Gosner (developmental stage) are deposited by the
mother directly in the water. Tadpoles emerge from the pouch openning,
which is located at the posterior end of dorsum.

Q. Is the process similar to the Surinam toad?

A. In general terms it is similar. But it is diferent because the marsupial
frog has a pouch whereas the Suriname toad has a skin protection for each
embryo. Also, the Suriname toad gaves birth to froglets, whereas this
species (Gastrotheca riobambae) gaves birth to tadpoles. There are other
species of marsupial frogs such as Gastrotheca plumbea (which is also being
breed by us at this time) which give birth to small froglets.

Q. Do you have photographs of the frogs exiting the females back? Will you be able to send photographs of this process.

A. Not as yet. The time of birth is difficult to document because it occurrs in water, and almost always at night. The females seem to require complete darkness to release the tadpoles. We have had many failed attempts to capture this process. In time we anticipate to capture this moment.