Animal Diversity Web

Ge­o­graphic Range

This species of frog is only found in the Black­all and Conon­dale Ranges in South­east­ern Queens­land, Aus­tralia (Barker, 1995).

• Biogeographic Regions
• australian
  • native

Habi­tat

This frog is mostly aquatic and is found in rocky creek beds, ad­ja­cent pools, and rock pools in the Aus­tralian rain­for­est. It also lives along the rocky streams of the moist eu­ca­lyp­tus for­est.

• Habitat Regions
• tropical
• freshwater

• Terrestrial Biomes
• forest
• rainforest

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools

• Wetlands
• marsh
• swamp

Phys­i­cal De­scrip­tion

The length of the oval-shaped R. silus ranges in fe­males from 45 to 54 mm, and 33 to 41 mm in males. Ex­tremely large eyes dor­sally pro­trude from its small, flat­tened head (Tyler, 1983). The skin color on its back ranges from dull gray to slate, with ob­scure dark and light patches. When the back­ground is pale, a broad brown and pos­te­ri­orly curved, su­pe­r­oc­u­lar bar is de­tectable (Barker, 1995). Its belly is marked with large creamy patches on a white sur­face. The feet of this frog are ex­ten­sively webbed to suit its aquatic lifestyle.

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger

• Range length

  33 to 54 mm

  1.30 to 2.13 in

De­vel­op­ment

Gas­tric brood­ing frog tad­poles de­velop in their mother's stom­ach for 6 to 7 weeks. The tad­poles do not feed dur­ing this time, as they lack tooth rows. The young de­velop at dif­fer­ent rates and are birthed when they are ready; ex­pelling all of the ju­ve­nile frogs may take sev­eral days.

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

The re­pro­duc­tive habits of the gas­tric brood­ing frog set it apart from other species. The breed­ing age for this frog is about two years. The process of egg de­po­si­tion and am­plexus has never been ob­served; it is only known that the eggs are in­gested through the mouth (Barker, 1995). The fe­male swal­lows be­tween 18 and 25 fer­til­ized cream-col­ored eggs, which de­velop in her stom­ach. Dur­ing this 6 to 7 week pe­riod, the col­or­less tad­poles lack tooth rows and do not feed. The fe­male also stops feed­ing en­tirely be­cause of the egg jelly and chem­i­cals se­creted by the tad­poles which switch off the pro­duc­tion of hy­drochlo­ric acid in the stom­ach wall (A.N.C.A., 1996). The en­tire di­ges­tive sys­tem shuts down, which pre­vents the di­ges­tion of the young. Birth is ac­com­plished by the fe­male widely open­ing her mouth and di­lat­ing her esoph­a­gus. The off­spring are pro­pelled from the stom­ach to the mouth, and then hop away.

The breed­ing sea­son oc­curs dur­ing the spring and sum­mer months. Though the warm tem­per­a­tures of these months aren't es­sen­tial for re­pro­duc­tion, rain and mois­ture are nec­es­sary (Tyler, 1983).

• Key Reproductive Features
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • external
• oviparous

• Range age at sexual or reproductive maturity (female)

  2 (low) years

• Range age at sexual or reproductive maturity (male)

  2 (low) years

Each fe­male gas­tric brood­ing frog con­tributes yolk to her eggs, and then after they are fer­til­ized, she swal­lows them and car­ries them in her stom­ach for 6 to 7 weeks. Dur­ing this time, her di­ges­tive sys­tem shuts down and she can­not eat. Once the young are fully de­vel­oped and ex­pelled from her mouth, she has no fur­ther con­tact with them. Male gas­tric brood­ing frogs con­tribute noth­ing to the next gen­er­a­tion ex­cept their sperm.

• Parental Investment
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • protecting
    • female

Lifes­pan/Longevity

In cap­tiv­ity, in­di­vid­ual R. silus have lived up to 3 years.

• Range lifespan
  Status: captivity

  3 (high) years

Be­hav­ior

These frogs are not very ac­tive and they often re­main in the same po­si­tion for sev­eral hours at a time. They are nei­ther strictly noc­tur­nal nor di­ur­nal (Tyler, 1983). They are fast and pow­er­ful swim­mers, but often just drift or float ven­tral side up in the water. Though aquat­i­cally adapted, they travel a great deal on land. They are only ca­pa­ble of leap­ing 25 cm, which makes them po­ten­tially easy prey.

• Key Behaviors
• terricolous
• saltatorial
• natatorial
• motile
• sedentary

Com­mu­ni­ca­tion and Per­cep­tion

The ad­ver­tise­ment call of the south­ern gas­tric brood­ing frog is a pulse with a slight up­ward in­flec­tion last­ing for 0.5 sec­onds, re­peated every 6 sec­onds.

• Communication Channels
• visual
• tactile
• acoustic
• chemical

• Other Communication Modes
• choruses

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

The diet of R. silus con­sists mainly of small live in­sects. Once the prey is cap­tured, the frog ma­nip­u­lates it fur­ther into the mouth with its fore­limbs. Soft-bod­ied in­sects are eaten at the water sur­face, while stronger prey are taken un­der­wa­ter for con­sump­tion. Rheo­ba­tra­chus silus has been ob­served catch­ing in­sects on land as well as in water (Tyler, 1983).

• Primary Diet
• carnivore
  • insectivore

• Animal Foods
• insects

Pre­da­tion

The two major preda­tors of R. silus, white-faced herons and eels, in­habit the same streams as the frogs. The leaves from eu­ca­lyp­tus trees and stones along the stream banks aid in hid­ing this species from preda­tors. When grasped, as an es­cape mech­a­nism, they ex­crete a coat of mucus that en­ables them to slip away.

• Known Predators

  • white-faced herons (Egretta novaehollandiae)
  • eels (Anguillidae)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

The abil­ity to shut down the se­cre­tion of pow­er­ful di­ges­tive acids could have an im­por­tant bear­ing in the med­ical treat­ment of hu­mans who suf­fer from gas­tric ul­cers.

Con­ser­va­tion Sta­tus

The gas­tric brood­ing frog has lim­ited dis­tri­b­u­tions, which has been detri­men­tal to its ex­is­tence. It is listed as en­dan­gered in the Ap­pen­dix of the Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species of Wild Fauna and Flora. In 1973, when this species was dis­cov­ered, they were ex­tremely abun­dant, and be­lieved com­mon. As­ton­ish­ingly, less than a decade after their dis­cov­ery, they seem­ingly dis­ap­peared with­out a trace. There are sev­eral spec­u­lated causes for the pop­u­la­tion crash: drought, over-col­lec­tion by her­petol­o­gists, habi­tat pol­lu­tion by the log­ging in­dus­try and by the damming of the creeks for the gold-pan­ning in­dus­try (Tyler, 1985). This species' per­me­able skin makes them es­pe­cially sus­cep­ti­ble to the pol­lu­tion in their aquatic en­vi­ron­ment.

This species is cur­rently listed as Ex­tinct by the In­ter­na­tional Union for the Con­ser­va­tion of Na­ture. No in­di­vid­u­als have been ob­served in the wild since 1981, de­spite ex­ten­sive searches.

• IUCN Red List

  Extinct
  More information

• IUCN Red List

  Extinct
  More information

• US Federal List

  No special status

• CITES

  Appendix II

Other Com­ments

Gas­tric brood­ing frogs can­not be tamed and al­ways strug­gle when han­dled.

Con­trib­u­tors

Erica Se­meyn (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Aus­tralian Na­ture Con­ser­va­tion As­so­ci­a­tion. 1996. http://​www.​anca.​gov.​au/​plants/​manageme/​frogprod.​htm.​

Barker, J., G.C. Grigg & M.J. Tyler. 1995. A Field Guide to Aus­tralian Frogs. Sur­rey Beatty & Sons. Chip­ping Nor­ton, Aus­tralia

Du­ell­man, W.E., Linda Trueb. 1986. Bi­ol­ogy of Am­phib­ians. Mc­graw-Hill Book Co. New York, New York.

Sanders, In­grid. 1996. Platy­pus Frog. http://​www-mugc.​cc.​monash.​edu.​au/​~ctemp3/platypus.​htm (link no longer valid)

Tyler, M.J. 1983. The Gas­tric Brood­ing Frog. Bid­dles Ltd. Great Britain.

Tyler, M.J., M. Davies. 1985. The Gas­tric Brood­ing Frog. The Bi­ol­ogy of Aus­tralian Frogs and Rep­tiles (pg 469-470).