Why Frogs?
The Research
Frog Facts
Why Frogs?
Frog populations are under grave threat of mass extinction, and this is a crucial time to raise awareness of their plight and of the measures that are being undertaken from multiple areas to assist them.
There are over 230 species of frog in Australia and more are being discovered. Just recently a tiny yet already considered endangered frog has been discovered in Nth NSW (as reported by both The ABC and The Guardian) and has been named Assa wollumbin sp.nov. in consultation with Aboriginal Elders of the Wollumbin Consultative Group. The NSW Government has declared the frog’s habitat an asset of intergenerational significance, a designation introduced after the 2019-20 bushfires for places that warrant special protection.
Creating safe refuges for frogs in the wild as well as developing captive breeding programs are key to averting more species loss. Whilst new species are being discovered, and new laws are passed to encourage protections.
Assoc. Professor Lee Berger is a prize winning scientist who is currently working closely with a range of environment agencies to understand the scale of the mass frog deaths across Australia, leading the research to understand the likely causes. Her research has uncovered the cause of dramatic declines of amphibians in natural areas, by discovering the novel pandemic disease, chytridiomycosis. Berger has applied her disease expertise for the benefit of conservation and is a world leader in understanding the epidemiology and pathogenesis of chytridiomycosis. As stated by the Australian Academy of Science, “Berger’s research has made a major contribution to the recognition that the spread of exotic disease is a threat to biodiversity and a serious consequence of globalization.”
Mortalities in the wild were especially bad in 2021, and as reported in The Guardian recently, scientists from the FrogID project and the Australian Registry of Wildlife Health have collected reports of 30 native species being affected, including endangered frogs such as green and golden bell frogs, southern bell frogs and the giant barred frog. The one non native species being affected was the cane toad. Since late July, the Frog ID team have collected 1,200 records of dead or dying frogs, about 70% of them in New South Wales and 22% in Queensland. The causes of these recent die-offs are still being investigated.
The Research by Lead Scientist Assoc/Prof Lee Berger
The aim of our research at the University of Melbourne is to enable our most endangered frogs to thrive in the wild again. Frog populations began declining in the late 1970’s. Because they naturally fluctuate in abundance, it took about 10 years before it was clear that species were disappearing.
The frog chytrid fungus escaped from Asia and spread around the world since the 1970s.
Frog populations in Australia and the Americas had little immunity to this introduced disease, and mass die-offs occurred leading to over 90 species becoming extinct.
The fungus grows best in cooler, wetter areas, and has had the worst impacts in the mountains along the great dividing range, while frogs in inland desert areas are not infected.
The fungus is waterborne, so the species most affected have been high altitude rainforest frogs and also alpine frogs that spend a lot of their life near the water.
The fungus grows inside skin cells of frogs, and completes its lifecycle in the time it takes for epidermal cells to mature and be shed from the surface.
Although its just a superficial infection, because frog skin is so permeable, when it is damaged frogs lose electrolytes and their blood sodium levels became dangerously low and they die.
When frogs disappear, animals that depend on them as food, such as snakes, also decline. And without tadpoles in the streams, mosquitoes increase and might be causing more diseases in humans.
The spread of the chytrid fungus around the world is likely a result of globalisation and increased movement and trade. The disease spread for more than 15 years before it was discovered.
Some frog species seem to be evolving resistance to the fungus, and are slowly moving back into their former habitats. Our most endangered species have very small populations and are running out of time to adapt. Our research is aimed at improving resistance in these frogs.
Science has been key to not only recognising the threats to our environment, but developing ways to conserve it. We need science so that decisions can be made based on truth rather than opinion.
Without science we would not have even known that frog populations around the world have disappeared, and the cause of their deaths.
This pandemic in frogs shows the value of protecting our borders with strong quarantine, as there are likely other diseases in wildlife that have not yet been discovered that we need to keep out. Along with feral animals and weeds, introduction of new diseases can be catastrophic.
Frog Facts by Herpetologist Danielle Wallace
Frogs play an important role in our ecosystem as both predator and prey. Frogs control insect populations by eating them, but frogs also serve as prey for animals like wetland birds, snakes and carnivorous mammals.
Frogs croak to communicate, and they do this by inflating their vocal sac, or throat, like a balloon to amplify their call. Generally only male frogs croak, and they perform their songs for female frogs in the hopes of attracting a mate.
Frogs have an incredible life cycle – they are amphibians, which means that they can live both in water and on land. The first stages of a frog’s life are aquatic – they start out their lives as a cluster of eggs laid in the water, and then hatch into swimming tadpoles. Over time, the tadpole develops back legs and then it starts to look more frog-like when the front legs emerge. Finally, the new froglet absorbs its tadpole tail and can start its new life out of the water.
Unlike people, frogs can take up air and water through their skin. The skin of a frog is very thin and permeable, which means water and gases can easily pass through into the frog’s body. So while we take in water by drinking a glass of water with our mouth, a frog can absorb water through their skin by simply sitting in a puddle.
Frogs are not very picky eaters. They will try to eat anything that moves and that they can shove into their mouths! A frog’s diet is mostly made up of insects and spiders, but they can also eat rodents and other, smaller frogs. Bigger frogs like green tree frogs have even been known to eat snakes and bats.
What can people do to help frogs?
There are lots of things people can do to help frogs. You can make a frog pond in your garden with native plants to encourage frogs to visit. If you don’t have a lot of space, you can make a frog hotel, which is some PVC tubes of different sizes put into a pot of water. Tree frogs love sleeping in tubes, and your frog hotel might soon have its first guests. When you go out for a bushwalk around ponds and creeks, you can also record any frogs you hear using the FrogID app, which is a great way to learn about your local frogs and contribute to frog science.
What are the main threats to our frog populations?
Unfortunately there are lot of threats facing our frog populations. Destruction of their habitat through development and logging is a major threat to frogs, and they can also be victims of roadkill when the try to cross busy roads to get to their pond or creek. But the biggest threat to frogs at the moment is the amphibian chytrid fungus. Chytrid fungus is a deadly disease that infects the skin of frogs, and has caused the rapid decline and extinction of many frog species.
Most tree frogs are able to change colour, and this colour change is often to do with the weather. When its warm, green tree frogs are usually a bright lime green, but when the weather cools down or the frog is not active, they can change colour to a dark chocolate brown. This also helps them camouflage in their environment and hide from predators.
Each species of frog has its own unique call, or ‘croak’. This makes it easy for frog scientists to tell which frog species live in a certain pond or creek. Frog calls can range in sound from the owl-like hoot of the giant burrowing frog, to the growl of the growling grass frog, to the weird clucking of the Wotjulum frog, or better known as the crazy chicken frog.
If you look at a video of a frog eating, you’ll notice that as it munches its food, its eyes close and scrunch up. This is because frogs use their eyeballs to help squash their food in their mouth. Not only are big frog eyes good for spotting prey, but the underside of a frog’s eyeballs protrude into its mouth to help the frog much down on their prey and swallow it.