Rheobatrachus silus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

View Printer Friendly

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AMPHIBIA	ANURA	MYOBATRACHIDAE

Scientific Name:

Rheobatrachus silus

Species Authority:

Liem, 1973

Common Name/s:

English

–

Southern Gastric Brooding Frog, Southern Platypus Frog

Assessment Information [top]

Red List Category & Criteria:

Extinct ver 3.1

Year Assessed:

2004

Assessor/s:

Ed Meyer, David Newell, Harry Hines, Sarah May, Jean-Marc Hero, John Clarke, Frank Lemckert

Reviewer/s:

Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson and Neil Cox)

Justification:
Listed as Extinct because it has not been recorded in the wild since 1981, and extensive searches over the last 25 years have failed to locate this species.

History:

2002	–	Extinct
1996	–	Critically Endangered (Baillie and Groombridge 1996)
1994	–	Endangered (Groombridge 1994)
1990	–	Endangered (IUCN 1990)
1988	–	Endangered (IUCN Conservation Monitoring Centre 1988)
1986	–	Vulnerable (IUCN Conservation Monitoring Centre 1986)

Geographic Range [top]

Range Description:	This species, an Australian endemic, was restricted to elevations between 350 and 800m asl in the Blackall and Conondale Ranges in south-east Queensland (Hines, Mahony and McDonald 1999). The geographic distribution of the species was less than 1,400km² (map in Hines, Mahony and McDonald 1999). Rheobatrachus silus inhabited streams in the catchments of the Mary, Stanley and Mooloolah River (Ingram 1983). It was thought to have been first found in 1972 (Liem 1973), but Ingram (1991) reported a specimen collected in 1914 from the Blackall Range.
Countries:	Regionally extinct: Australia
Range Map:	(click map to view full version)

Population [top]

Population:	The species declined rapidly and disappeared at about the same time as a sympatric species Taudactylus diurnus (Czechura and Ingram 1990). Czechura and Ingram (1990) and Ingram (1990) state that the last frog was seen in the wild in 1979 on the Conondale Range. However, Richards, McDonald and Alford (1993) reported the existence of a specimen taken from the Blackall Range in 1981. Despite intensive searching, the species has not been located since (Ingram and McDonald 1993; Hines, Mahony and McDonald 1999). In the laboratory, the last known individual died in 1983 (Tyler and Davies 1985b). Ingram (1983) studied a population of the species in the headwaters of Booloumba Creek, Conondale Range, and estimated that approximately 78 were present in 1976. No other estimates of population size are available for the species. This species is now believed to be extinct.

Population:

The species declined rapidly and disappeared at about the same time as a sympatric species Taudactylus diurnus (Czechura and Ingram 1990). Czechura and Ingram (1990) and Ingram (1990) state that the last frog was seen in the wild in 1979 on the Conondale Range. However, Richards, McDonald and Alford (1993) reported the existence of a specimen taken from the Blackall Range in 1981. Despite intensive searching, the species has not been located since (Ingram and McDonald 1993; Hines, Mahony and McDonald 1999). In the laboratory, the last known individual died in 1983 (Tyler and Davies 1985b). Ingram (1983) studied a population of the species in the headwaters of Booloumba Creek, Conondale Range, and estimated that approximately 78 were present in 1976. No other estimates of population size are available for the species. This species is now believed to be extinct.

Habitat and Ecology [top]

Habitat and Ecology:	Rheobatrachus silus lived in rainforest, wet sclerophyll forest and riverine gallery open forest at 350m asl and was closely associated with watercourses and adjacent rock pools and soaks (Czechura 1991; Meyer< Hines and Hero 2001e). These streams are mostly perennial, but in extremely dry years they may cease to flow (Ingram 1983). The vegetation along the stream banks is usually closed forest or tall closed forest with emergent eucalypts, although there are some sites in open forest with grassy ground cover (Ingram 1983). 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 (Ingram 1983). The species was also found under rock in shallow water in backwaters and also the main flow of permanent watercourses (Ingram 1983; Czechura 1991). Searches of popular sites in winter only recovered two frogs and it is assumed that the species hibernates in deep crevices in rocks or spaces between rocks underwater during the colder months (Ingram 1983). 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 (Ingram 1983). The prerequisite for the use of pools by this species seems to be that the pool must be deep enough for the frog to be able to sit with its head out of the water and be able to safely submerge (Ingram 1983). Individuals will only sit fully exposed on the rocks during light rain (Ingram 1983). Rheobatrachus silus has never been recorded from cleared riparian habitat. Breeding activity occurs between October and December (Ingram 1983). Males call from rock crevices above pools (Ingram 1983). Females brood young within the stomach and give birth through the mouth (Tyler and Carter 1982). Fertilized eggs or early stage larvae are presumably swallowed by the female and complete their development in the stomach (Tyler and Carter 1982). The number of eggs in gravid females (approximately 40) exceeds the number of juveniles found to occur in the stomach (21-26) (Tyler 1989). It is not known whether or not the excess eggs are digested by the female or whether or not they are simply not swallowed (Tyler 1989). The production of hydrochloric acid in the stomach of the female ceases during brooding (Tyler et al. 1983). Tadpoles develop in a manner similar to the aquatic tadpoles of other species though, as they feed off egg yolk, the labial teeth are absent and the intestines form at a later stage of development (Tyler 1989). After 6-7 weeks the females give birth to up to 25 young (Tyler and Davies 1983a). Young emerge from the female’s mouth as fully formed frogs and after four days the digestive tract returns to normal and the female recommences feeding (Tyler and Davies 1983b). 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.
Systems:	Terrestrial; Freshwater

Habitat and Ecology:

Rheobatrachus silus lived in rainforest, wet sclerophyll forest and riverine gallery open forest at 350m asl and was closely associated with watercourses and adjacent rock pools and soaks (Czechura 1991; Meyer< Hines and Hero 2001e). These streams are mostly perennial, but in extremely dry years they may cease to flow (Ingram 1983). The vegetation along the stream banks is usually closed forest or tall closed forest with emergent eucalypts, although there are some sites in open forest with grassy ground cover (Ingram 1983). 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 (Ingram 1983). The species was also found under rock in shallow water in backwaters and also the main flow of permanent watercourses (Ingram 1983; Czechura 1991). Searches of popular sites in winter only recovered two frogs and it is assumed that the species hibernates in deep crevices in rocks or spaces between rocks underwater during the colder months (Ingram 1983). 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 (Ingram 1983). The prerequisite for the use of pools by this species seems to be that the pool must be deep enough for the frog to be able to sit with its head out of the water and be able to safely submerge (Ingram 1983). Individuals will only sit fully exposed on the rocks during light rain (Ingram 1983). Rheobatrachus silus has never been recorded from cleared riparian habitat. Breeding activity occurs between October and December (Ingram 1983). Males call from rock crevices above pools (Ingram 1983). Females brood young within the stomach and give birth through the mouth (Tyler and Carter 1982). Fertilized eggs or early stage larvae are presumably swallowed by the female and complete their development in the stomach (Tyler and Carter 1982). The number of eggs in gravid females (approximately 40) exceeds the number of juveniles found to occur in the stomach (21-26) (Tyler 1989). It is not known whether or not the excess eggs are digested by the female or whether or not they are simply not swallowed (Tyler 1989). The production of hydrochloric acid in the stomach of the female ceases during brooding (Tyler et al. 1983). Tadpoles develop in a manner similar to the aquatic tadpoles of other species though, as they feed off egg yolk, the labial teeth are absent and the intestines form at a later stage of development (Tyler 1989). After 6-7 weeks the females give birth to up to 25 young (Tyler and Davies 1983a). Young emerge from the female’s mouth as fully formed frogs and after four days the digestive tract returns to normal and the female recommences feeding (Tyler and Davies 1983b). 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.

Systems:

Terrestrial; Freshwater

Threats [top]

Major Threat(s):	The reason(s) for the disappearance of this species remains unknown (Tyler and Davies 1985b). Populations were present in logged catchments between 1972 and 1979. Although the species persisted in the streams during these activities, the effects of timber harvesting on this aquatic species were never investigated. Its habitat is currently threatened by feral pigs, invasion of weeds (especially mistflower Ageratina riparia), and altered flow and water quality due to upstream disturbances (Hines, Mahony and McDonald 1999). However, from what is known from similar declines and disappearances elsewhere in the world, the disease chytridiomycosis must be suspected.

Major Threat(s):

The reason(s) for the disappearance of this species remains unknown (Tyler and Davies 1985b). Populations were present in logged catchments between 1972 and 1979. Although the species persisted in the streams during these activities, the effects of timber harvesting on this aquatic species were never investigated. Its habitat is currently threatened by feral pigs, invasion of weeds (especially mistflower Ageratina riparia), and altered flow and water quality due to upstream disturbances (Hines, Mahony and McDonald 1999). However, from what is known from similar declines and disappearances elsewhere in the world, the disease chytridiomycosis must be suspected.

Conservation Actions [top]

Conservation Actions:	The historical range of the species included several protected areas. Further research into the cause of the decline of this species is needed. It is listed on CITES Appendix II.

Conservation Actions:

The historical range of the species included several protected areas. Further research into the cause of the decline of this species is needed. It is listed on CITES Appendix II.

Citation:	Ed Meyer, David Newell, Harry Hines, Sarah May, Jean-Marc Hero, John Clarke, Frank Lemckert 2004. Rheobatrachus silus. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 08 February 2012.
Disclaimer:	To make use of this information, please check the <Terms of Use>.
Feedback:	If you see any errors or have any questions or suggestions on what is shown on this page, please fill in the feedback form so that we can correct or extend the information provided