Category Archives: amphibians

Bleak future for Australian frogs

In recent years, scientists have become increasingly aware of a worldwide decline in the numbers of frogs. Frogs are certainly disappearing in Australia. Eight frog species have become extinct in the last 25 years, and several more are likely to become extinct in the near future.

There have been drastic declines in the populations of amphibians, particularly frogs, throughout the world. Along the east coast of Australia, nine species of frog have totally disappeared in the past two decades, and scientists are at a loss to explain why or provide solutions – except for ‘human activities’ and population growth – but some reasons are still elusive.

Victoria’s frogs are facing a conservation crisis according to biologists, who warn that some of the state’s amphibians have “passed a tipping point”, while others have become extinct.

Baw_Baw_Frog-large(image: Baw Baw frog)

Nick Clemann, program leader (threatened fauna) at the Arthur Rylah Institute , said the prospects for the Baw Baw frog, Victoria’s only endemic frog species, were now considered “immediately bleak”.

The frog is now only found on the forested western slopes of the mountain. It’s tiny, it breeds underground and it can only be found in Victoria’s eastern Alpine region of Mount Baw Baw and one highly protected shipping container in inner Melbourne.

The spotted tree frog, found in rocky mountain streams in north-eastern Victoria, is also battling shrinking numbers, with more than half the known populations believed lost. Those that remain and are being monitored and are showing a gradual decline. Their survival is threatened by chytridiomycosis, the waterborne disease attacks the keratin in the skin and threatens all frog species. There is no effective infection control for the fungus in the wild.

To help combat the decline of Baw Baw frogs, Melbourne Zoo converted a shipping container that simulates alpine conditions, and has succeeded in establishing a small ‘insurance’ population base of 57 frogs.

The southern corroboree frog is one of Australia’s most endangered species. Arguably one of the most striking of Australia’s species, the southern corroboree frog is endemic to Australia, and in fact only lives in small pockets entirely within Kosciuszko National Park. ‘Corroboree’ refers to a meeting or gathering of Aboriginal Australians where participants often adorn themselves in white striped markings.

Southern_Corroboree_frog(image: Corroboree frog)

Threats include human impacts such as climate change, fire and habitat disturbance, as well as feral animals. But the biggest problem is the chytrid fungus (Batrachochytrium dendrobatidis), which has been decimating frog populations around the world.

Frogs, more than any other terrestrial animal, need water to survive. In inland wetlands in NSW, water can be scarce for years and then suddenly abundant, and frogs depend on the flooding of wetlands to successfully breed.

Eighteen species of wetland and river frogs – a quarter of all frogs in NSW – are listed under the Threatened Species Conservation Act 1995. They include the green and golden bell frog, southern bell frog , stuttering frog, corroboree frogs, alpine tree frog, sphagnum frog and wallum froglet.

Exotic fish threats
The plague minnow (Gambusia holbrookii) is a small fish sometimes called the mosquito fish. It was originally introduced to control mosquitoes but was not successful in doing this. It is now common and widespread, and known to eat native frog eggs and tadpoles.

Other exotic fish – such as trout, carp and goldfish – also eat native frog eggs and tadpoles.

Other threats

  • Loss of habitat: Humans can damage frog habitat in many ways. For example, people:clear large areas of native vegetation for housing and agriculture.
  • removal of fallen timber, leaf litter and other ground cover
  • drain wetlands or allow cattle to graze in them
    collection of bush rock, which is used for shelter by some frogs such as the red-crowned toadlet
  • frequently burn patches of bush which frogs shelter in reduce the quality of wildlife corridors, which connect areas of frog habitat. This makes it difficult for frogs to move from one area to another.

In our Western, consumer-based economy, underpinned by high population growth, there’s heavy competition for development of frog habitats.

Displaced and introduced frogs pose a serious risk of spreading disease to local native species

‘Banana box‘ frogs are displaced frogs that have been inadvertently moved from their normal habitat, usually in containers of fresh produce or landscape supplies. As displaced frogs pose a serious risk of spreading disease to local native species, they must be treated as if they are carrying an infectious disease and must never be released into the wild unless special approval is given.
http://www.environment.nsw.gov.au/animals/ThreatsToFrogs.htm

An estimated 6000-8000 frogs are transported to Melbourne annually in produce. These tropical frogs cannot survive in Victoria’s cool climate nor can they be returned to their home state due to fears of spreading disease. These displaced frogs are cared for at the Victoria Frog Group’s and Amphibian Research Centre’s
Lost Frogs’ Home,
nursed back to health in quarantine and eventually placed into a caring home as a family pet.

Cane toads
The culling of cane toads has been widely encouraged as they are displacing native Australian frogs.
Some of our native Australian frogs look a bit like cane toads. Cane Toads are large heavily-built amphibians with dry warty skin. They have a bony head and over their eyes are bony ridges that meet above the nose. They can be distinguished from some native Australian frogs because they sit upright and are active in the daytime in dense clusters.

Deadly urban sprawl

The Growling Grass Frog, for example, is endangered in Victoria. It needs habitat corridors along creeks and waterways, such as Merri Creek, to survive and flourish.

Studies by Melbourne University researcher Dr Geoff Heard show that the frog’s population has declined by 29 per cent in Melbourne’s north since 2001-02. The Growling Grass Frog conservation corridor along the Merri will be narrowed to only 50m wide and straddled by the town centre of Lockerbie, north of Craigieburn. Melbourne’s northern growth corridor will gain 11,000 new houses with the development of the former Lockerbie sheep station. Construction is due to start within months on a new community that will eventually house 30,000 people at Kalkallo, north of Craigieburn.

Growling_Grass_Frog(image: Growling Grass Frog)

It is estimated more than $986 million will be collected over the 30 to 40 years it will take to develop the growth corridors . The money will go towards buying land for reserves and management of the sites.

The government will also release strategies to protect key species threatened by Melbourne’s growth, including the endangered growling grass frog and golden sun moth.

Somehow, planners will have the contradictory task of trying to save endangered specie, yet at the same time promote housing growth! In the land famous for extinctions, the competition between housing/economic growth, and the protection of habitats for native species, continues to untangle, but the latter are always hindsight consideration – and collateral damage!

Ecological role of amphibians

A good ecosystem is the one with many species variety whereby it has less chances of being extremely damaged by natural disasters like climate changes or even human interaction. So as to help to keep the system healthy, each and every species has a niche in its ecosystem.
Frogs mainly feed on insects as their main sustenance and also native pests whereby with this, the insect and pests population is regulated which could have been hazardous to the rest of the environment if it was not kept down. Forest streams have leaf litter as their main source of energy where animals feed on leaves and nutrients get released as a result of tadpole activity that becomes an advantage to microorganisms, algae and other animals.

(featured image: Growling Grass frog)

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Growling Grass Frog growls for attention as Melbourne’s growth corridors threaten annihilation

By Sheila Newman, reprinted from Candobetter.net website.

This scientific study into the endangered Growling Grass Frog was released overnight and looks at how the genetic diversity of the frog is being negatively impacted by the rapid urbanisation of Melbourne’s fringe. They were once very abundant in Victoria (so abundant that they used to feed them to the snakes the Melbourne Zoo!) and now only a few populations exist around Melbourne.

The scientists have found a population of the frogs in the Cardinia Shire, which has an increased genetic diversity that they hope to protect.

Claire Keely, the lead scientist on the paper, is both a PhD student and part of the Live Exhibits team at the Melbourne Museum (where they have some of the pretty green frogs in question).

Scientific study finds the vulnerable Growling Grass Frog under increasing threat from rapid urbanisation in Melbourne. (Download paper as full pdf publication here: /files/Genetic stucture and diversity of the endangered growling grass frog in a rapidly urbanizing region.pdf)

A paper by scientists from Museum Victoria and The University of Melbourne has today been published in the Royal Society of London Open Science journal. It describes how the Growling Grass Frog’s genetic diversity is being negatively impacted by rapid habitat loss as Melbourne’s urban fringe continues to expand.

Growling_Grass_Frog_(Litoria_raniformis)_(8615947746)

Urbanisation is a leading cause of species extinction worldwide and is considered a major threat to global biodiversity.

The Growling Grass Frog is listed as vulnerable to extinction in Australia, but isolated populations still persist in the greater Melbourne area. Many of these populations are located in the city’s proposed urban growth area, causing concern as the species is known to be sensitive to habitat fragmentation caused by urbanisation.

The study found that there is decreased genetic diversity in the remaining populations found in Wyndham, Melton and Hume-Whittlesea, making the frogs more prone to inbreeding and less able to cope with the threats posed by urbanisation. The scientists have also found that populations in the Cardinia Shire, one of the four regions studied, are genetically distinct.

“Genetic diversity is key to maintaining the population of Growling Grass Frogs in Victoria as it makes them more resilient to the threats posed by urbanisation. If they are to survive in greater Melbourne the population found in Cardinia will require separate conservation management,” said Claire Keely, PhD student, Museum Victoria and The University of Melbourne, who led the study.

This study demonstrates the importance of genetic research on vulnerable species and can be used to inform conservation efforts to maintain populations.

The team are currently looking to gain further funding to extend the study into the Gippsland region in order to find out more about the frog species genetic diversity and how the Cardinia populations are related to those further east.

The Growling Grass Frog is one of the largest frog species in Australia. They are found in south eastern Australia and were once so abundant in Victoria that they were used for dissections in universities and to feed the snakes the Melbourne Zoo.

For interviews, images, video footage or to meet a Growling Grass Frog at the Melbourne Museum please get in contact.

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