The Southern Corroboree Frog occurs only in a very restricted habitat within NSW and, with as few as 200 adult frogs left in the wild, it is listed as critically endangered.
Scientists assume that a range of factors are causing the decline, including habitat destruction, climate change, increased UV-B radiation, introduced species, infectious disease (including Chytrid fungus), pollutants, and their synergistic interactions the most commonly documented.
Climate change affects the snow and rainfall patterns in the alpine ecosystem. This can, in addition to naturally high mortality over the winter period, result in high mortality of eggs in nests.
The fungal disease chytridiomycosis is a very serious threat to all native frogs. It is highly contagious and infection is always fatal. There is evidence that Southern Corroboree Frog populations have been exposed to the disease.
There is no guarantee that it will be possible to save the Corroboree Frog, but scientists and the Foundation for National Parks & Wildlife decided to make an effort while we still have the chance.
In 2001 the Foundation directed funds from its Endangered Species Appeal towards a captive breeding program for the Northern Corroboree Frog at the Amphibian Research Centre (ARC) in Victoria.
Over a period of eight years scientists nurtured a captive population in case the species disappeared altogether in the wild. Eggs and adults from the captive population have already been released back into the wild.
In 2009, the Southern Corroboree Frog was listed as Australia’s most critically endangered anuran amphibian, and was predicted to go extinct in the wild within the next two to three years.
As a result, the Foundation funded a project undertaken by Monash University to undetake the in vitro fertilization of Corroboree Frogs, so that this species could be bred under controlled laboratory conditions and population numbers increased.
The study has now been successfully completed and has provided critical insights into how Assisted Reproductive Technologies (ART) might be used to assist with the captive breeding of the Corroboree Frog.
Three important findings were made. First, it was established that luteinizing hormone-releasing hormone (LHRHa) was significantly more effective than human chorionic gonadotropin (hCG) at inducing males to release sperm.
Second, it was discovered that LHRH a could be used to induce females to release eggs. Third, IVF trials were attempted and resulted in the successful fertilisation of hormonally induced eggs.
Unfortunately, however, all resultant embryos failed during early development.
One explanation for embryo failure is that the incubation conditions employed were inappropriate. An alternative and more plausible explanation is that parental genotypes were genetically incompatible.
Animals used in the experiments were obtained from mixed source populations so genetic dissimilarity may have prevented successful embryo development.
The findings of the FNPW research have been recently published in the top tier international journal Reproductive Biology and Endocrinology.
The scientists have deemed the project highly successful because it has provided critical data on how Corroboree frogs respond to the application of exogenous hormones.
Future research will now need to focus on refining hormone induction protocols and understanding the effects of intrinsic genetic factors and/or incubation conditions on embryos growth, development and survival.
It is anticipated that this research will play a key role in the conservation of Corroboree frogs, and other critically endangered anuran amphibians.
Visit http://www.corroboreefrog.org.au/ to find out more about this species and efforts to save it from extinction.
This project was supported by grants from theNSW Office of Environment and Heritage (OEH), theCorroboree Frog Conservation Trust, the Murray Catchment Management Authority (Murray CMA) and the Foundation for National Parks and Wildlife (FNPW). The research was also supported by Abbott Australia.
The project was part of a multi-pronged recovery program for the Southern Corroboree Frog. The recovery team includes experts from the NSW Office of Environment and Heritage (Dr David Hunter), the Amphibian Research Cente (Dr Gerry Marintelli and Erika Marintelli), Taronga Zoo (Dr Peter Harlow and Michael McFadden), Tidbinbilla Nature Reserve (Murray Evans), Healesville Sanctuary (Kristy Penrose), Melbourne Zoo (Raelene Hobbs), and the Murray Catchment Management Authority (Elisa Tack).
