Recently Extinct Animals - Species Info - Southern Gastric-brooding Frog

Rheobatrachus silus		HOME

Kingdom	Animalia	Unknown copyright licence.
Phylum	Chordata
Class	Amphibia
Order	Anura
Family	Myobatrachidae
Authority	Liem, 1973

English Name	Southern Gastric-brooding Frog, Conondale Gastric-brooding Frog, Platypus Frog
Dutch Name	Zuidelijke Maagbroedkikker
French Name	Grenouille Plate à Incubation Gastrique
German Name	Australische Magenbrüterfrosch
Spanish Name	Rana Incubadora Gástrica de Australia
Swedish Name	Magruvargroda

Characteristics	The colour of this oval-shaped frog’s dorsal surface was brown, or olive brown to almost black, and it had obscure dark and light patches. A dark streak runs from the eyes to the base of the forelimbs, and it has darker crossbars on the limbs. The ventral surface is white or cream with yellow markings on their limbs. The skin is finely granular above, and smooth below. The snout is blunt and rounded, with nostrils and eyes directed upwards. The eyes are large, prominent, and located close together and close to the front of the head. These frog’s fingers lack webbing, while their toes are extensively webbed to suit its aquatic lifestyle. Their digits have small discs. The males of this species had a length of 30-44mm, and the females had a length of 41-54mm. Their call is a loud staccato, consisting of 30-34 pulses repeated in a long series, lasting 260-290 minutes. The dominant frequency is 1000 hz, with less emphasises frequency bands a 500, 700, 1200, and 1400 hz.

Lifestyle	These frogs are not very active and remain in the same position for several hours at a time. 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. When grasped, as an escape mechanism, they excrete a coat of mucus that enables them to slip away. This species is neither strictly nocturnal nor diurnal. In captivity this frog could not be tamed and always struggle when handled.

Range & Habitat	This species was restricted to elevations between 400-800 m in the Blackdall and Conondale Ranges in southeastern Queensland, Australia. The geographical distribution of the species was less than 1400 km². This frog is mostly aquatic and has never been located more than 4m from water. This species is found rocky creek beds, adjacent pools, and rock pools in the rainforest and tall open forest with a closed under storey. It also lives along the rocky streams of the moist eucalyptus forest. It prefers rock pools and backwaters with leaf litter and rocks in which to shelter from predators, like white-faced herons and eels. In spring and summer, individuals were usually found in or at the edge of rock pools, either amongst leaf litter, under and between stones or in crevices around the edge. These frogs were also found under rock in shallow water in backwaters and also the main flow of permanent watercourses. Adult males tend to prefer deeper pools, whereas females and juveniles may move to newly created pools after rain as long as these pools contained stones and/or leaf litter. Searches of popular sites in winter only recovered two frogs and it assumed that the species hibernates in deep crevices in rocks or spaces between rocks underwater during the colder months.

Food	The diet of the southern gastric-brooding frog consists mainly of small live insects. Once a 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 is taken underwater for consumption. This species has been observed catching insects on land as well as in water. In an aquarium situation in captivity the frog ate Lepidopterans, Dipterans and Neuropterans.

Reproduction	The breeding age of this frog was about 2 years. Breeding activity occurs between October and December, and appears dependent on summer rains. Males call from rock crevices above pools. The process of egg deposition and amplexus has never been observed. (Amplexus is the process when the male frog grasps the female while she lays her eggs. At the same time, he fertilizes them with the fluid containing sperm.) Image: a female brooding frog with a young in her mouth. Unknown copyright licence. Fertilised eggs or early stage of larvae were presumably swallowed by the female and complete their development in the stomach (gastric-brooding). The number of eggs in gravid females (approximately 40) exceeds the number of juveniles found to occur in the stomach (21-26). It is not known whether the female digests the excess eggs or whether they are simply not swallowed. The production of hydrochloric acid (digestive secretion) in the stomach of the female is ceased by hormones produce by the young. The entire digestive system shuts down, which prevents the digestion of the young. The colourless tadpoles develop in a manner similar to the aquatic tadpoles of other frog species though. They feed of egg yolk. The labial teeth are absent and the intestines form at a later stage of development. After 6-7 weeks the females give birth to up to 25 young, birth is accomplished by the female widely opening her mouth and dilating her gullet (oesophagus). The young are propelled from the stomach to the mouth, and than hop away. They emerge from the female’s mouth as fully former frogs and after 4 days the digestive tract of the female returns to normal and she recommences feeding. Ingram (1983) reported minimum brooding periods from two individuals of 36 and 43 days and suggested that the duration was such that females were unlikely to breed twice in one season.

History & Population	The southern gastric-brooding frog was thought to have been discovered in 1972, and described by Liem in 1973. However, in 1991 Ingram reported a specimen collected in 1914 from the Blackall Range. Ingram studied a population of the species in the head waters of Booloumba Creek, Conondale range, and estimated that approximately 78 frog were present in 1976. No other estimated of the species’ population size are available. The southern gastric-brooding frog population underwent an unanticipated decline in the winter of 1979. The last frog on the Conondale Range was seen in 1979. The last sighting of this species in the wild occurred in September 1981 on the Blackall Range. The last known individual died in captivity in a laboratory in November 1983. Despite intensive searching, the species has not been located since.

Extinction Causes	The reason(s) for the disappearance of this species remains unknown. The scientists Tyler and Davies (1985) found no obvious evidence that over-collecting, pollution from logging or gold panning, or drought was responsible for the population decline. Current research is examining the possibility that a fungus may have caused the decline of this species. The frog’s habitat is currently threatened by feral pigs, the invasion of weeds (especially mistflower Ageratina riparia), and altered flow and water quality due to upstream disturbances. New information from: Queensland Museum - Why are our frogs disappearing? In 1993, two leading Queensland researchers (Glen Ingram, then of the Queensland Museum and Keith McDonald of the then Department of Environment) wrote: "In Queensland since 1978, seven species of frogs have disappeared and populations of another four have seriously declined. All the declines have occurred in upland rainforest and all the species live along or breed in streams. We ask the question "what is wrong with upland rainforest streams" and answer "nobody knows". We note the 14 years elapsed from the time of the first disappearance in 1979 until intensive research began into the cause, or causes, of the declines. We ask "why" and conclude that the reasons were scepticism and a lack of interest in the plight of frogs. Finally we appeal for thought: there appear to be many clues to the solution of the problem of the declines." In October 1999, the situation has changed. After many years of painstakingly detailed field monitoring, breeding/ maintenance in captivity experiments and pathology testing, three likely causes for these declines have emerged. The first may be global warming. The second appears to be a micro-organism, a 'fungus' (Phylum Chytridiomycota of the Kingdom Protoctista). The third is undoubtedly people-related habitat destruction and degradation. All may be linked. This problem is of major concern to everyone passionate about conservation of biodiversity. It is not confined to Queensland or Australia. Similar declines have been reported in North and South America, Europe, and South Africa, all areas where there are active biological research communities. In areas such as south east Asia and New Guinea, where monitoring has not been possible, no one can say whether or not frog populations are secure. Nearly 20 years after this problem was first reported, a picture is emerging of why it has occurred. Yet to be determined, however, is the full-extent of the problem. Most critical is finding out what can be done to combat it and to find missing species or restore those nearly lost.

Conservation Attempts	The species is listed as endangered in the Appendix of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Their Queensland legislative status is endangered as well. One southern gastric-brooding frog has been kept in captivity for three years until it died in 1983; so captive breeding was not an option. A recovery plan has been prepared and searches continue. Sadly enough this all could not prevent its disappearance and the species is still not rediscovered.

Museum Specimens	The Australian Museum has a specimen of the southern day frog, see Australian Museum Collections - Herpetology Collection Gallery - Eungella Gastric Brooding Frog. Please email me with more information on museum specimens.

Relatives	The only other gastric-brooding frog was the northern gastric-brooding frog or Eungella gastric-brooding frog, Rheobatrachus vitellinus. This frog was last observed in March 1985, and is now considered extinct too.

Links	Australian Museum Collections - Herpetology Collection Gallery - Eungella Gastric Brooding Frog. IUCN Red List of Threatened Species - Rheobatrachus silus Southern gastric-brooding frog - Rheobatrachus silus - ARKive Animal Diversity Web: Rheobatrachus silus: Information AmphibiaWeb - Rheobatrachus silus - Southern Gastric Brooding Frog
Last updated: 18^th July 2004. This page is a part of The Extinction Website. © 2000-2009.