We name the 26 Australian frogs at greatest risk of extinction by 2040 — and how to save them

Spotted tree frog.
Michael Williams/Its A Wildlife Photography, Author provided

Graeme Gillespie, The University of Melbourne; Conrad Hoskin, James Cook University; Hayley Geyle, Charles Darwin University; Jaana Dielenberg, Charles Darwin University; Nicola Mitchell, The University of Western Australia, and Stephen Garnett, Charles Darwin UniversityAustralia is home to more than 240 frog species, most of which occur nowhere else. Unfortunately, some frogs are beyond help, with four Australian species officially listed as extinct.

This includes two remarkable species of gastric-brooding frog. To reproduce, gastric-brooding frogs swallowed their fertilised eggs, and later regurgitated tiny baby frogs. Their reproduction was unique in the animal kingdom, and now they are gone.

Our new study published today, identified the 26 Australian frogs at greatest risk, the likelihood of their extinctions by 2040 and the steps needed to save them.

Tragically, we have identified an additional three frog species that are very likely to be extinct. Another four species on our list are still surviving, but not likely to make it to 2040 without help.

#1 The northern gastric-brooding frog (Rheobatrachus vitellinus) is likely already extinct, primarily due to chytrid fungus disease.
Hal Cogger

The 26 most imperilled frogs

The striking yellow-spotted tree frog (in southeast Australia), the northern tinker frog and the mountain mist frog (both in Far North Queensland) are not yet officially listed as extinct – but are very likely to be so. We estimated there is a greater than 90% chance they are already extinct.

The locations of the top 26 Australian frogs at risk of extinction. ** Species likely to be recently extinct. * Species more likely than not to become extinct by 2040 unless there is action.
Jaana Dielenberg/Threatened Species Recovery Hub

The next four most imperilled species are hanging on in the wild by their little frog fingers: the southern corroboree frog and Baw Baw frog in the Australian Alps, and the Kroombit tinker frog and armoured mist frog in Queensland’s rainforests.

The southern corroboree frog, for example, was formerly found throughout Kosciuszko National Park in the Snowy Mountains. But today, there’s only one small wild population known to exist, due largely to an introduced disease.

Without action it is more likely than not (66% chance) the southern corroboree frog will become extinct by 2040.

#6 The southern corroboree frog (Pseudophryne corroboree) is close to extinction.
David Hunter/DPIE NSW

#3 The yellow-spotted tree frog (Litoria castanea) is likely extinct. It was once common throughout the New England Tableland and Southern Tablelands region in NSW, and the ACT. It is sensitive to chytrid fungus disease and also impacted by climate change, habitat loss and invasive fish.
David Hunter/DPIE NSW

What are we up against?

Species are suffering from a range of threats. But for our most recent extinctions and those now at greatest risk, the biggest cause of declines is the amphibian chytrid fungus disease.

This introduced fungus is thought to have arrived in Australia in the 1970s and has taken a heavy toll on susceptible species ever since. Cool wet environments, such as rainforest-topped mountains in Queensland where frog diversity is particularly high, favour the pathogen.

The fungus feeds on the keratin in frogs’ skin — a major organ that plays a vital role in regulating moisture, exchanging respiratory gases, immunity, and producing sunscreen-like substances and chemicals to deter predators.

Chrytrid disease killed this green-eyed tree frog.
Robert Puschendorf

#8 Armoured mist frog (Litoria lorica) populations have been decimated by chytrid fungus disease. It has been lost throughout former mountainous rainforest habitats where the fungus thrives. Without effective action, it’s likely to be extinct within 20 years.
Conrad Hoskin

Another major emerging threat is climate change, which heats and dries out moist habitats. It’s affecting 19 of the imperilled species we identified, such as the white-bellied frog in Western Australia, which develops tadpoles in little depressions in waterlogged soil.

Climate change is also increasing the frequency, extent and intensity of fires, which have impacted half (13) of the identified species in recent years. The Black Summer fires ravaged swathes of habitat where fires should rarely occur, such as mossy alpine wetlands inhabited by the northern corroboree frog.

Invasive species impact ten frog species. For the spotted tree frog in southern Australia, introduced fish such as brown and rainbow trout are the main problem, as they’re aggressive predators of tadpoles. In northern Australia, feral pigs often wreak havoc on delicate habitats.

#15 The Kuranda tree frog (Litoria myola) is found in a very small area near Cairns. Its primary threat is loss and degradation of habitat due to development.
Conrad Hoskin

#20 The white-bellied frog (Geocrinia alba) is the Western Australian frog at greatest risk of extinction. The tadpoles of this tiny terrestrial breeding frog rely on wet soil to develop. Reduced rainfall is contributing to declines.
Emily Hoffmann

So what can we do about it?

We identified the key actions that can feasibly be implemented in time to save these species. This includes finding potential refuge sites from chytrid and from climate change, reducing bushfire risks and reducing impacts of introduced species.

But for many species, these actions alone aren’t enough. Given the perilous state of some species in the wild, captive conservation breeding programs are also needed. But they cannot be the end goal.

#11 A northern corroboree frog in the captive breeding program run by the ACT Government.
Peter Taylor/Threatened Species Recovery Hub

Captive breeding programs can not only establish insurance populations, they can also help a species persist in the wild by supplying frogs to establish populations at new suitable sites.

Boosting numbers in existing wild populations with captive bred frogs improves their chance of survival. Not only are there more frogs, but also greater genetic diversity. This means the frogs have a better chance of adapting to new conditions, including climate change and emerging diseases.

Our knowledge of how to breed frogs in captivity has improved dramatically in recent decades, but we need to invest in doing this for more frog species.

Please save these frogs: The 26 Australian species at greatest risk of extinction.

Finding and creating wild refuges

Another vital way to help threatened frogs persist in the wild is by protecting, creating and expanding natural refuge areas. Refuges are places where major threats are eliminated or reduced enough to allow a population to survive long term.

For the spotted-tree frog, work is underway to prevent the destruction of frog breeding habitat by deer, and to prevent tadpoles being eaten by introduced predatory fish species. These actions will also help many other frog species as well.

The chytrid fungus can’t be controlled, but fortunately it does not thrive in all environments. For example, in the warmer parts of species’ range, pathogen virulence may be lower and frog resilience may be higher.

Chytrid fungus completely wiped out the armoured mist frog from its cool, wet heartland in the uplands of the Daintree Rainforest. But, a small population was found surviving at a warmer, more open site where the chytrid fungus is less virulent. Conservation for this species now focuses on these warmer sites.

This strategy is now being used to identify potential refuges from chytrid for other frog species, such as the northern corroboree frog.

Dr Graeme Gillespie during a survey for the spotted-tree frog.
Michael Williams/Its A Wildlife Photography

No time to lose

We missed the window to save the gastric-brooding frogs, but we should heed their cautionary tale. We are on the cusp of losing many more unique species.

Decline can happen so rapidly that, for many species, there is no time to lose. Apart from the unknown ecological consequences of their extinctions, the intrinsic value of these frogs means their losses will diminish our natural legacy.

In raising awareness of these species we hope we will spark new action to save them. Unfortunately, despite persisting and evolving independently for millions of years, some species can now no longer survive without our help.

Graeme Gillespie, Honorary Research Fellow, The University of Melbourne; Conrad Hoskin, Lecturer/ABRS Postdoctoral Fellow, James Cook University; Hayley Geyle, Research Assistant, Charles Darwin University; Jaana Dielenberg, University Fellow, Charles Darwin University; Nicola Mitchell, Associate Professor in Conservation Physiology, The University of Western Australia, and Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Advertisement

Dead, shrivelled frogs are unexpectedly turning up across eastern Australia. We need your help to find out why

Green Tree Frog
Jodi Rowley, Author provided

Jodi Rowley, Australian Museum and Karrie Rose, University of SydneyOver the past few weeks, we’ve received a flurry of emails from concerned people who’ve seen sick and dead frogs across eastern Victoria, New South Wales and Queensland.

One person wrote:

About a month ago, I noticed the Green Tree Frogs living around our home showing signs of lethargy & ill health. I was devastated to find about 7 of them dead.

Another wrote:

We previously had a very healthy population of green tree frogs and a couple of months ago I noticed a frog that had turned brown. I then noticed more of them and have found numerous dead frogs around our property.

And another said she’d seen so many dead frogs on her daily runs she had to “seriously wonder how many more are there”.

So what’s going on? The short answer is: we don’t really know. How many frogs have died and why is a mystery, and we’re relying on people across Australia to help us solve it.

Why are frogs important?

Frogs are an integral part of healthy Australian ecosystems. While they are usually small and unseen, they’re an important thread in the food web, and a kind of environmental glue that keeps ecosystems functioning. Healthy frog populations are usually a good indication of a healthy environment.

The stony creek frog is one of the species hit by this mysterious outbreak.
Jodi Rowley, Author provided

They eat vast amounts of invertebrates, including pest species, and they’re a fundamental food source for a wide variety of other wildlife, including birds, mammals and reptiles. Tadpoles fill our creeks and dams, helping keep algae and mosquito larvae under control while they too become food for fish and other wildlife.

But many of Australia’s frog populations are imperilled from multiple, compounding threats, such as habitat loss and modification, climate change, invasive plants, animals and diseases.

Although we’re fortunate to have at least 242 native frog species in Australia, 35 are considered threatened with extinction. At least four are considered extinct: the southern and northern gastric-brooding frogs (Rheobatrachus silus and Rheobatrachus vitellinus), the sharp-snouted day frog (Taudactylus acutirostris) and the southern day frog (Taudactylus diurnus).

A truly unusual outbreak

In most circumstances, it’s rare to see a dead frog. Most frogs are secretive in nature and, when they die, they decompose rapidly. So the growing reports of dead and dying frogs from across eastern Australia over the last few months are surprising, to say the least.

While the first cold snap of each year can be accompanied by a few localised frog deaths, this outbreak has affected more animals over a greater range than previously encountered.

This is truly an unusual amphibian mass mortality event.

In this outbreak, frogs appear to be either darker or lighter than normal, slow, out in the daytime (they’re usually nocturnal), and are thin. Some frogs have red bellies, red feet, and excessive sloughed skin.

A browned, shrivelled green tree frog (Litoria caerulea)
Suzanne Mcgovern, Author provided

The iconic green tree frog (Litoria caeulea) seems hardest hit in this event, with the often apple-green and plump frogs turning brown and shrivelled.

This frog is widespread and generally rather common. In fact, it’s the ninth most commonly recorded frog in the national citizen science project, FrogID. But it has disappeared from parts of its former range.

Other species reported as being among the sick and dying include Peron’s tree frog (Litoria peronii), the Stony Creek frog (Litoria lesueuri), and green stream frog (Litoria phyllochroa). These are all relatively common and widespread species, which is likely why they have been found in and around our gardens.

We simply don’t know the true impacts of this event on Australia’s frog species, particularly those that are rare, cryptic or living in remote places. Well over 100 species of frog live within the geographic range of this outbreak. Dozens of these are considered threatened, including the booroolong Frog (Litoria booroolongensis) and the giant barred frog (Mixophyes iteratus).

The giant barred frog is a threatened species that lives in the geographic range of this outbreak.
Jodi Rowley, Author provided

So what might be going on?

Amphibians are susceptible to environmental toxins and a wide range of parasitic, bacterial, viral and fungal pathogens. Frogs globally have been battling it out with a pandemic of their own for decades — a potentially deadly fungus often called amphibian chytrid fungus.

This fungus attacks the skin, which frogs use to breathe, drink, and control electrolytes important for the heart to function. It’s also responsible for causing population declines in more than 500 amphibian species around the world, and 50 extinctions.

For example, in Australia the bright yellow and black southern corroboree frog (Pseudophryne corroboree) is just hanging on in the wild, thanks only to intensive management and captive breeding.

The teeny tiny southern corroborree frogs have been hit hard by the chytrid fungus.
Jodi Rowley, Author provided

Curiously, some other frog species appear more tolerant to the amphibian chytrid fungus than others. Many now common frogs seem able to live with the fungus, such as the near-ubiquitous Australian common eastern froglet (Crinia signifera).

But if frogs have had this fungus affecting them for decades, why are we seeing so many dead frogs now?

---

Read more:
A deadly fungus threatens to wipe out 100 frog species – here’s how it can be stopped

---

Well, disease is the outcome of a battle between a pathogen (in this case a fungus), a host (in this case the frog) and the environment. The fungus doesn’t do well in warm, dry conditions. So during summer, frogs are more likely to have the upper hand.

In winter, the tables turn. As the frog’s immune system slows, the fungus may be able to take hold.

Of course, the amphibian chytrid fungus is just one possible culprit. Other less well-known diseases affect frogs.

The near-ubiquitous Austrlaian common eastern froglet is one species that seems able to live with the devastating chytrid fungus.
Jodi Rowley, Author provided

To date, the Australian Registry of Wildlife Health has confirmed the presence of the amphibian chytrid fungus in a very small number of sick frogs they’ve examined from the recent outbreak. However, other diseases — such as ranavirus, myxosporean parasites and trypanosome parasites — have also been responsible for native frog mass mortality events in Australia.

It’s also possible a novel or exotic pathogen could be behind this. So the Australian Registry of Wildlife Health is working with the Australian Museum, government biosecurity and environment agencies as part of the investigation.

Here’s how you can help

While we suspect a combination of the amphibian chytrid fungus and the chilly temperatures, we simply don’t know what factors may be contributing to the outbreak.

Why green tree frogs are dying en masse is still a mystery.
Sophie Hendry, Author provided

We also aren’t sure how widespread it is, what impact it will have on our frog populations, or how long it will last.

While the temperatures stay low, we suspect our frogs will continue to succumb. If we don’t investigate quickly, we will lose the opportunity to achieve a diagnosis and understand what has transpired.

We need your help to solve this mystery.

Please send any reports of sick or dead frogs (and if possible, photos) to us, via the national citizen science project FrogID, or email calls@frogid.net.au.

---

Read more:
Clicks, bonks and dripping taps: listen to the calls of 6 frogs out and about this summer

---

Jodi Rowley, Curator, Amphibian & Reptile Conservation Biology, UNSW, Australian Museum and Karrie Rose, Australian Registry of Wildlife Health – Taronga Conservation Society Australia, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Disappearing Frogs

Amphibians: Only About Half are Known to Science

The article below suggests that about half of the world’s amphibians are yet to be made known to science and that they could become extinct before they are. It is a very interesting article.

For more visit:
http://theconversation.edu.au/articles/half-the-worlds-amphibians-yet-to-be-discovered-1903