frogs

Listening to nature's subtle cues

I was visiting the St Kilda Botanical Gardens when a storm was approaching; the air felt electric. The sun disappeared behind dark, all-consuming clouds, and lightning could be seen cracking through the grey sky. My senses were heightened and from a nearby pond in the gardens I could hear the 'Creee... cree creee cree creee' of Southern Brown Tree Frogs calling. Then the rain started to fall, delicately splashing my face.

How do you experience, or sense a change in the weather?

These days, we are bombarded with weather updates, warnings and other information from our electronic devices, televisions, and even Siri and Google Home. In nature, animals and plants have evolved inbuilt systems to detect changes in the weather and react accordingly. For thousands of years, people have used some of these animals to predict changes in the weather.

By becoming more mindful and paying closer attention to nature, we can detect oncoming changes in the weather. There are several examples to draw on. Many insects hide away when a storm is brewing; black ants make themselves busy by covering up holes to their nests if rain is on the way; and there is even a saying, ‘when sheep gather in a huddle, tomorrow will have a puddle.’ One of the other well-known cues in nature is taken from frogs, as their evening choruses are generally a sign that rain is on the way.

Southern Brown Tree Frogs are often heard prior to rainfall in and around Melbourne.  Image: Rowan Mott

Southern Brown Tree Frogs are often heard prior to rainfall in and around Melbourne. Image: Rowan Mott

When it comes to frogs, the events of reproduction must be synchronised with suitable conditions, so breeding can be successful. We can take advantage of this time and listen carefully to the unique calls of male frogs “wooing” the females to their pond. Many frog species breed seasonally, and are thought to use temperature, day length, moisture and atmospheric pressure (“weight of the air”) to time their breeding activity. The final trigger for most frogs is rainfall, as many species require free-standing water for fertilisation.

There are several local species in Melbourne that you may hear prior to a rainfall event. Here are a few examples to spark your interest.

The Southern Brown Tree Frog (Litoria ewingii) is a species that has adapted to urbanised habitats, and can be found from the city to the suburbs and beyond. The adults inhabit a variety of wet and flooded areas, and fortunately for us they are common in gardens and suburban areas. Southern Brown Tree Frogs can also be found calling long distances from water. The good news for us is they call all year round, and often in response to rain. So, next time you're out and you hear a series of rapid, whirring, pulsing notes, repeated 5 to 15 times – ‘creeeeeee creee creee cree cree cree’ (the first note is usually the longest) – it might be wise to grab a raincoat!

Another helpful frog is the Eastern Banjo Frog or Pobblebonk (Limnodynastes dumerilii). This species can call all year round, but has a peak in its calling period during spring and early summer. Keep your ear out for a short explosive note producing a resonant ‘bonk’. The call is usually repeated every few seconds. This fascinating species can migrate up to one kilometre to its breeding sites. It is also a burrowing species, commonly popping up in suburban gardens and sandpits where you may glimpse it foraging on the surface after rain. 

The Eastern Banjo Frog is also known as the Pobblebonk and can call all year round.  Image: Cathy Cavallo

The Eastern Banjo Frog is also known as the Pobblebonk and can call all year round. Image: Cathy Cavallo

The Eastern Banjo Frog can migrate up to one kilometre to their breeding sites.  Image: Cathy Cavallo

The Eastern Banjo Frog can migrate up to one kilometre to their breeding sites. Image: Cathy Cavallo

Lastly, we come to frogs that alert us to the autumn rain Melbourne often experiences. One of the more common species you may come across is the Victorian Smooth Froglet (Geocrinia victoriana). I’ve recorded Victorian Smooth Froglets at Yarra Bend Park in Kew, and in the outer-eastern suburbs. The male frogs can be heard from low-lying areas within gullies, at the edge of wetlands and waterways (such as among moist leaf litter) that will flood after rain. They are a secretive species, and need an inquisitive ear to seek out their lovely and very distinctive call. Their song consists of a long, harsh first note, followed by a long series of short, rapidly repeated musical notes – ‘wa-a-a-a-a-ark pip-pip-pip-pip-pip-pip...’.

Not all frogs are “pond breeders”. The Victorian Smooth Froglet is an exception to the rule and is referred to as a terrestrial breeder for their curious and intriguing reproductive habit. Within a low-lying moist area, the male calls from a shallow burrow and the female will lay her eggs in the burrow on land, not in the water. Much of the development is done within the egg capsule. Once the rain floods their burrow, the tadpoles can emerge and complete their metamorphosis in free-standing water. Males will often call prior to or at the onset of a heavy rain event throughout March to May. The other not-so-common terrestrial breeders that call in autumn are the elusive Southern Toadlet (Pseudophyryne semimarmorata) and Bibron’s Toadlet (Pseudophryne bibronii); they have very similar double-note calls with an inflection on the second note – ‘ri-rick’.

So, next time you want to ask Siri what the weather will be like, perhaps take a walk outside in your local park and see if the frogs are calling. They may be telling you in their own lovely, melodic way to take an umbrella to work today.

You can investigate other pond-breeding frogs in Melbourne that may alert you to the onset of rain throughout the year. Take a look at frogs.org.au and the Melbourne Water Frog Census. You can also download the Melbourne Water Frog Census app or check out the recently launched Australia-wide Frog ID app. Both apps encourage citizens to record frog calls, so scientists can have a greater understanding of frogs around Australia and track their populations over time.


Christina Renowden has had an affinity for nature since she was a child. Over the years this love of nature has morphed into one role or another, including studying conservation ecology, researching urban frogs, and working as a consultant zoologist. She is now a mother of two and the founder of Leap into Nature. Since 2014, Leap into Nature has been creating and presenting a range of nature-based and environmental education programs for young people. Christina is excited to begin a Master of Environment in July 2018 at the University of Melbourne and is currently the Vice President on the committee of management for Environment Education Victoria. 


Banner image courtesy of Rowan Mott.

Our Home in the Wilderness

The wind outside comes and goes in fits of undirected rage. It hurtles past my window and drowns out the calls of the fledgling raven in the tree outside. Squat and downy, it grips swaying branches with fresh, uncertain claws. Yesterday it was marvellously sunny outside, and now… well, it isn’t. Such variable weather is an oft-cited trademark of Melbourne and surrounds, and is something Melbournians enjoy brandishing as a testament to the fact that we live in a land of extremes. Yet, for the young raven outside, Melbourne’s weather is perhaps one of the least extreme of the forces that influence its daily life. 

Indeed, all cities – not just Melbourne  – are places of stark contrasts. Worlds of conflict and polarity, where squat and downy lives must eke out an existence. As Associate Professor Kirsten Parris writes in her new book Ecology of Urban Environments, cities are ‘where the best and worst of human existence can be found, and where habitats constructed for people can complement or obliterate the habitats of other species.’ To study these contrasts and complements is to study urban ecology: a relatively young discipline and one that Parris defines as ‘the ecology of all organisms – including humans – in urban environments’.

Few fields of study could be more relevant to the life of the young raven outside my window, and fewer still could hold such timely pertinence for the contemporary hominid that sits at his computer writing about it from within warm walls. For, the world around us is changing and if we are to preserve ourselves, as well as our squat and downy friends, we must have knowledge. Parris captures the essence of our transformation of the planet – no more obvious than in urban environments – with a preface in the form of a poem by Mark Knopfler:

A long time ago came a man on a track
Walking thirty miles with a sack on his back
And he put down his load where he thought it was best
Made a home in the wilderness

And so goes the story across the planet. A story that began some twelve thousand years ago in the Middle East and one that has been repeated and reenacted at an ever-increasing rate across the globe. ‘Globally,’ writes Parris, ‘there were 740 urban areas with a human population >500,000 in 2008, including 22 with a population >10 million’.

In some regard, I’ve come to treat my copy of this text in the same manner my parents regarded our family medical book. We once saw that book as an essential tool for diagnosing illness and subsequently, treated it in accordance with the expert advice contained therein. Yet, in many ways what Parris has written is far more relevant to my life than such a medical text. That old, dusty book had information on any number of illnesses likely and unlikely to occur to the average human. Meanwhile, the issues and processes Parris describes are almost all relevant to any one of us, and at any given time. It is accessible too and while perfect for students, researchers, and policy-makers, I can’t help but feel it belongs on the shelf of the “average” family. What is written here can be seen, and heard, out my window: the construction of urban infrastructure including many surfaces impervious to rainfall, the removal of native vegetation and the planting of exotics, the hum of road traffic, the streets lights, the runoff, the waste, the dogs and the cats and the net-entangled fruit bats. This is a book about you and me and the community in which we are apart.

That community is shaped by our own actions – something we are often naive to. I can recall receiving noise complaints from neighbours whilst living in an apartment building – perhaps I was reading too loud – but the complaints of the natural world are often less obvious without the adequate training. Parris goes some way to highlighting our subtler but no less significant impacts, and provides some serious food for thought: ‘Human preferences … influence patterns of activity in different parts of a city, such as which places are visited, when, by how many people, and what they do there.’ For example: ‘Nature enthusiasts may be most likely to walk through parks of remnant patches of native vegetation in spring and summer, potentially trampling plants or disturbing breeding birds.’

The ever-hungry, black shape huddled in the tree outside is testament to the unequal impacts of urbanisation on our native biodiversity. Ravens cope well in urban environments– hell, they cope well under most circumstances – but many species do not, and as Parris notes, ‘The particular characteristics of urban habitats can result in the formation of novel ecological communities, some of which have no obvious analogues in natural environments.’

This inequality of the urban realm extends to our species also, and Parris dedicates an entire chapter to this subject. As Knopfler puts it:

Then came the mines, then came the ore
Then there was the hard times, then there was a war…
I used to like to go to work but they shut it down
I got a right to go to work but there’s no work here to be found

Parris highlights several relatable issues, such as access to urban parks and open spaces, the unequal distribution of noise and air pollution, and the dependence those of us living towards the edges of urban sprawl have on cars for transportation.

And the birds up on the wires and the telegraph poles
They can always fly away from this rain and this cold

And there’s the rub. Just like the poem’s narrator, we have but one home and ‘We’re gonna have to reap from some seed that’s been sowed’. Knopfler’s poem is an ominous tale of socio-economic downfall in big cities, and Parris does well to include it in her text. The impacts we are having on the natural world spin a no less foreboding yarn, and this book is an essential start to crafting a happier ending.  

Maybe my squat and downy friend outside will one day fly away, but there seem fewer and fewer places left for it to go where it won’t be touched by an urban world.   

This book belongs on your bookshelf if... you care to understand the processes at play around you and your home. 

Head to the Wiley website to purchase your copy. 


Chris McCormack
Chris recently graduated from The University of Melbourne with a Master's of Science in Zoology. He is the current Managing Director of Wild Melbourne and pursues his interests in science and natural history through the mediums of film, photography and written communication. 

You can find him on Twitter @Chris_M_McC

Species of the Month: October

Pobblebonk Frog (Limnodynastes dumerilii)

Credit: http://ashdown4628.clients.cmdwebsites.com/blog/wp-content/uploads/2012/03/Pobblebonk_02.jpg

Credit: http://ashdown4628.clients.cmdwebsites.com/blog/wp-content/uploads/2012/03/Pobblebonk_02.jpg

Named for its unusual call, the Pobblebonk Frog, also known as the Eastern Banjo Frog (Limnodynastes dumerilii) is common throughout our city's suburbs. You may find one in a backyard pond, or even in a garden bed while digging! 

The Pobblebonk is found throughout Victoria and Tasmania, but also west to Adelaide and north along the coast of New South Wales. One subspecies, L. dumerilii dumerilii is found throughout the northern and western suburbs of Melbourne, while L dumerilii insularis is found throughout the eastern and southern suburbs. Eastern Banjo Frogs  inhabit a range of environments, including woodlands, rainforests, farmlands, coastal areas and urban regions. These frogs live in and around the still water bodies found in swamps, dams streams and lakes. 

The Pobblebonk Frog can be up to 85mm long, often with a warty appearance that can cause them to be confused for the dreaded Cane Toad (Rhinella marina). They can vary greatly in colour, ranging from dark browns and blacks to olive green. Pobblebonks have a pale, yellow stripe from the eye to the top of the front leg and there may also be a pale stripe down their back.  This species lacks webbing between the toes, but has a shovel-like toe on each rear foot to aid them in burrowing. The most defining features of the Pobblebonk include a prominent tibial gland on the lower portion of each rear leg, and fleshy metatarsal tubercles  (fleshy lumps) on each hind foot.

Mating occurs from August all the way through to April. Females are able to lay up to four thousand eggs, which they deposit into a large, white, floating raft that made from mucous and bubbles. These rafts are usually found concealed in aquatic vegetation. Depending on water temperature (which affects metabolic rates), tadpoles can take up to fifteen months to fully develop. When they hatch, pobblebonk tadpoles are large, dark brown or black, with dark grey or brown fins.

This species of frog has a call that sounds like a plucked banjo string: a resonant ‘bonk’ sound. Nearly all year round these calls can be heard, especially after heavy rains. Males call every few seconds, usually from the shelter of floating aquatic vegetation, but also less regularly from the waters edge. During dryer spells, Pobblebonks will burrow themselves into the ground with their well equipped back feet, and wait for rain. 

Author: Emma Walsh


White Cypress-Pine (Callitris columellaris)

Credit: http://www.pfaf.org/Admin/PlantImages/CallitrisColumellaris2.jpg

Credit: http://www.pfaf.org/Admin/PlantImages/CallitrisColumellaris2.jpg

Many Melbournians are familiar with the ornamental juniper and fir trees that you find in many suburban gardens, or with the pine trees that we decorate at Christmas time. These are all foreign species, however there are a few gymnosperm species that are native to Victoria. Furthermore, there is just one gymnosperm that is indigenous to Melbourne: the White Cypress-pine (Callitris columellaris).

What is a gymnosperm I hear you ask? Gymnosperms are the primitive cousins of the flowering plants, the angiosperms.  They differ to flowering plants in that they do not produce flowers and instead produce cones, and that the ovule is not enclosed in an ovary. In species that are monoecious (hermaphroditic) individuals bear both male and female cones, while in dioecious species male and female cones are only found on individuals of their respective genders. Male and female cones are easily distinguished by their size: the male, pollen-producing cones are smaller than their female, ovule-bearing counterparts. Gymnosperms rely mostly on wind pollination, not insect pollination like many flowering plants.

There are four plant phyla that represent the gymnosperms, and by far the largest and most diverse is the Coniferophyta. Also known as conifers, members of the Coniferophyta are monoecious, deciduous (or evergreen) and have needle- or scale-like leaves. Some of the better-known conifer groups include the spruces, firs, pines and redwoods. Victoria is home to six conifer species, the Mountain Plum-pine (Podocarpus lawrencei), the Port Jackson Pine (Callitris rhomboidea), the Black Cypress-pine (Callitris endlicheri), the Scrub Cypress-pine (Callitris verrucosa), the Slender Cypress-pine (Callitris preissii), and of course, the White Cypress-pine (Callitris columellaris).

The White Cypress-pine (also known as Callitris glaucophylla) is a slender, conical tree with a single straight trunk with thick greyish bark and scale-like leaves. It’s female cones are relatively small and round, while it’s male cones are so small that they appear to be the dead ends of the leaves. The White Cypress-pine was originally widespread across Australia, but its distribution has been altered post-European settlement by domestic livestock and feral animal grazing, altered fire regimes and invasive weeds. Today its distribution is largely fragmented, with much of it’s Victorian range managed as forest reserves. White Cypress-pines are indigenous to the northern suburbs of Melbourne, namely Maribyrnong, Diggers Rest and Bulla. The good place to find the White Cypress-pine in its natural habitat is in the Organ Pipes National Park in Keilor North, northwest of the CBD.

This species is generally found in areas with sandy, well-drained soils. It does not survive in finer soils due to its susceptibility to water logging.  White Cypress-pines are extremely drought tolerant, and often develop fine ‘feeder roots’ in the upper few inches of soil for added water absorption. Although this species is hardy in dry conditions, it is sensitive to fire. Tree crowns will not regenerate and seed output can be suppressed for up to five years after being damaged by fire. Seedlings are also vulnerable to fire, as well as introduced herbivores such as sheep, goats and rabbits.

In the past aboriginal communities have used the timber of the White Cypress-pine to make spears, spear throws and paddles, and have mixed its resin with kangaroo dung to create an adhesive. It’s bark and foliage were also used as insect repellent.

It is easy to overlook conifers when considering iconic indigenous plants because they aren’t as pleasing to the eye as their angiosperm counterparts, but I find them fascinating because of the way they endure and persist in an environment where flowering plants are so dominant. White Cypress-pine is our ONLY indigenous gymnosperm, stoically holding its own against the countless angiosperms that call Melbourne home. 

Author: Emma Walsh