Southern gastric-brooding frog

Rheobatrachus silus

Queensland Legislative Status: Endangered



Endemicity: Queensland Endemic



Description: A moderately large, aquatic frog, males 30-44mm,

females 41-54mm (Ingram 1983, Tyler & Davies 1983a). Dorsal

surface is brown, or olive brown to almost black, usually with

obscure darker blotches on the back. A dark streak runs from the

eye to base of the forelimb. There are darker cross-bars on the

limbs, and pale and dark blotches and variegations on the digits

and webbing. Ventral surface is white or cream with yellow

markings on limbs. Skin is shagrened or finely granular above,

and smooth below. Snout is blunt and rounded, with the eyes and

nostrils directed upwards. Eyes are large and prominent, located

close together and close to front of head. Tongue is largely

adherent to the floor of mouth. Typanum is hidden. Fingers lack

webbing, while toes are fully webbed. Digits have small discs.

(Cogger 2000, Liem 1973, Tyler & Davies 1983a).



Call: Call is a loud staccato, consisting of 30-34 pulses repeated

in a long series, lasting 260-290 min/s. Dominant frequency is

1000 Hz, with less emphasises frequency bands at

500,700,1200 and 1400 Hz (Tyler 1983b).



Tadpole : Unknown



Reproduction : Breeding activity occurs between October and

December and appears dependent on summer rains (Ingram

1983). This species features a unique reproductive mode in

which eggs or early larvae are swallowed by the female and

complete their development in the stomach (Tyler & Carter 1982).

Hormones produced by the young inhibit the digestive secretions

of the stomach and inactivate the upper intestine, a process of

special interest to the medical community (Tyler 1984). Larvae

rely on yolk reserves throughout development (Tyler & Davies

1983b). Up to 25 young are brooded in this fashion, emerging

from the mother's mouth as fully formed metamorphs about 6-7

weeks (Tyler & Davies 1983b). the digestive tract returns to its

normal state and the female recommences feeding within four

days (Tyler 1983a). Maximum longevity is at least 3 years (Ingram

1983).





Habitat : Rheobatrchus silus is an aquatic species and has

never been located more than 4m from water. This species is

restricted to rocky perennial streams, soaks and pools in

rainforest and tall open forest with a closed understorey. It prefers

rock pools and backwaters with leaf litter and rocks in which to

shelter (Ingram 1983).

Rheobatrachus silus is most active during the warmer months,

between September and April, abundance decreasing as

conditions become drier in winter (Ingram 1983). It is not known

where these individuals go during this period, but it is believed

they hibernate in deep crevices in the rocks (Ingram 1983, Liem

1973, McDonald pers obs). Individuals may be active night or

day, particularly after rain. They establish home ranges in and

around suitable pools, spending extended periods partly

submerged and immobile. When heavy rain falls the males move

away from the water, sometimes up to four metres, and call from

sheltered hollows or crevices above the pools (Ingram 1983).



Distribution : Rheobatrachus silus is restricted to elevations of

400-800m in the Blackall and Conondale Ranges, south-eastern

Queensland. Rheobatrachus silus has not been sighted in the

wild since 1981 and may be extinct. Continued efforts to relocate

the species have failed (Hines et al.1999).



Latitude: Between 26º 34' and 27º 47';

Longitude: Between 152º 32' and 152º 53'.



Status : R. silus is one of five species of upland rainforest

stream-dwelling frogs which has declined in south-eastern

Queensland during the last 18 yrs (Ingram & McDonald 1993).

The species underwent an unanticipated decline in winter 1979

(Tyler & Davies 1985, Czechura & Ingram 1990) and the last

sighting occurred September 1981 (Richards et.al. 1993).

Searches have continued unsuccessfully, most recently in

November 1999 (Ingram & McDonald 1993, H. Hines pers

comm). Last known specimen died in captivity November 1983

(Tyler & Davies 1985).



Threatening Processes : The causes of the population decline

remain unknown. Tyler & Davies (1985) found no obvious

evidence that over collecting, pollution from logging or gold

panning, or drought were responsible for the population decline.

Current research is examining the possibility that a fungus may

have caused the decline of this species (Berger et al 1998,

Berger et al 1999). Information on disease investigations and

management can be located at

http://www.jcu.edu.au/school/phtm/PHTM/frogs/ampdis.htm.

The Gastric-Brooding Frog (Rheobatrachus silus) is an Australian casualty. It was only discovered 25 years ago in 1973. It is probably extinct already! This frog is unique. The female lays her eggs and swallows them so the tadpoles develop in her stomach. After 6 weeks about 25 young froglets are "born" through their mother's mouth as perfectly formed miniature frogs. While the tadpoles are growing in her stomach their mother shuts down her digestive juices and she doesn't eat. She is so full of tadpoles that her lungs don't have room to work so she absorbs oxygen through her skin. A week after her babies are born she starts to eat again. These frogs are olive-brown, almost black, with dark patches on the back, a whitish belly and some bright orange on their limbs. The males are 4 cms long and the females are 5 cms. Their fingers are long and slender, pointed and unwebbed and their toes are fully webbed. Gastric-brooding frogs feed at night by catching beetles, flies, mosquitoes and other insects with their long broad tongue. They live beside rocky mountain streams in eucalypt forests, hiding under rocks during the day and sitting on them, partly submerged at night. They are strong swimmers but will also drift in the water and sometimes float on their backs. Not you usual frog! Found only in a few mountain streams in the Blackall and Conondale Ranges of south-east Queensland, these frogs have not been seen in the wild since 1980. The last captive Rheobatrachus silus Gastric-Brooding Frog died at the Department of Zoology at the University of Adelaide in 1983, where it had been kept for research for 5 years. Two months after it died, another species of Gastric-Brooding Frog Rheobatrachus Vitellinus was discovered 800kms to the north. This one is bright yellowish-orange on the belly and under the arms, is pale brown, slightly larger than the other one and lives in fast, flowing creeks near the boundary of the Eungella National Park. It has not been seen in the wild since soon after its discovery. (Information from Taronga Zoo Education leaflets: GENERAL INFORMATION ON TWELVE AUSTRALIAN ENDANGERED SPECIES ----ENDANGERED NOW...EXTINCT FOREVER)

Source: http://www.env.qld.gov.au/cgi-bin/w3-msql/environment/plant/animals/resultframe.html?id=74

96 page booklet about disappearing Australian Frogs at http://www.ea.gov.au/biodiversity/threatened/information/frogs/pubs/frogs.pdf

For additional information, why not look up this book or CD:

http://www.naturesound.com.au/frogsse.htm The frog calls on this compact disc cover nearly all species in subtropical eastern Australia.

http://www.entosupplies.com.au/Books/Zoology/Reptiles_Amphibians/BT14Cthere.htm There's a Frog in my Stomach / Tyler, M.J.

An easy reading, non-technical account of the Gastric Brooding Frog of Southeast Queensland known to

brood its young in its stomach.