Southern gastric-brooding frog  (Rheobatrachus silus)

Classified as Extinct (EX) by the IUCN Red List 2007 (1), and listed on Appendix II of CITES (3).

Only recently discovered, this Australian frog is now believed to be extinct. The body was grey on the back with variable darker and lighter patches, whilst the underparts were white with large creamy markings. There was a dark streak running from the eye to the forelimbs. The small, flattened head featured large, protruding eyes and the toes were fully webbed (2) (4).

Endemic to Australia, the southern gastric-brooding frog was first discovered in 1973, and occurred only in the Conondale and Blackall Ranges of southeastern Queensland at an altitude between 400 and 800 metres (2). No wild specimens have been recorded since 1981, and the last captive individual died in 1983 (4).

This species was aquatic; it inhabited rainforest creeks, pools and streams (2).

The common name of this species refers to the extraordinary method of parental care. Mating occurred in the spring and the female then swallowed the eggs (4). Thus the larvae developed in her stomach; safe from digestion as the digestive system shut down completely (5). For the entire six to seven weeks of egg development the female did not eat, and when the young had metamorphosed into tiny frogs, they were expelled into the mouth and then crawled out and hopped away (4).

Feeding occurred both on land and in the water; small insects (2) were caught with the tongue, and the forelimbs were then used to manoeuvre the item into the mouth (2). The gastric-brooding frog was a strong swimmer, but it was not very active and often stayed still for hours, drifting or floating in the water (2).

The southern gastric-brooding frog was first discovered in 1973, but it had vanished from the wild less than a decade later in 1981 (4). A number of explanations have been proposed to explain this startling decline, including drought, climate change and increased ultra-violet radiation (6). Since the end of the 1970s, a total of 14 frog species endemic to Australia have undergone dramatic and sudden declines, reflecting the global decline in amphibian populations. Recent analysis has indicated that the simultaneous declines of these species may be the result of a fungal infection (7).

The southern gastric-brooding frog has been listed as Extinct by the Environment Protection and Biodiversity Conservation Act (EPBC) (2), and as Endangered in Queensland (4). Sadly, it seems likely that the secrets of this frog’s amazing ability to ‘switch off’ the secretion of digestive acids have been lost forever.

For more information on the southern gastric-brooding frog see:

• Environmental Protection Agency/ Queensland Parks and Wildlife Service:
  www.epa.qld.gov.au/nature_conservation/wildlife/threatened_plants_and_animals/endangered/southern_gastricbrooding_frog/

• Frogs Australia Network:
  www.frogsaustralia.net.au/frogs/display.cfm?frog_id=84

Authenticated (25/06/03) by Harry Hines, Queensland Parks and Wildlife Service.
http://www.epa.qld.gov.au

• Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
• Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
• Metamorphosis: an abrupt physical change from the larval to the adult form.

1. IUCN Red List (February, 2008)
   http://www.iucnredlist.org
2. Hines, H. (2002) Recovery plan for stream frogs of south-east Queensland 2001-2005.Environmental Protection Agency, Queensland, Australia. . Available at: http://www.environment.gov.au/biodiversity/threatened/publications/recovery/stream-frogs/pubs/stream-frogs.pdf
3. CITES (December, 2002)
   http://www.cites.org
4. Environment Protection Agency/ Queensland Parks and Wildlife Service (June, 2003)
   http://www.epa.qld.gov.au/nature_conservation/wildlife/threatened_plants_and_animals/endangered/southern_gastricbrooding_frog/
5. Amphibia Web (February, 2002)
   http://elib.cs.berkeley.edu/aw
6. Hines, H. (2003) Pers. comm.
7. Hyatt, A., Anstis, M., Gillespie, G., Herring, R., Hines, H., Mahony, M., Roberts, M., Roberts, D. and Woods, R. (2006) Threat Abatement Plan: Infection of amphibians with chytrid fungus resulting in chytridiomycosis.Department of the Environment and Heritage, Australia. Available at: http://www.environment.gov.au/biodiversity/threatened/publications/tap/chytrid/index.html