Croak! December 2020
From the editor
The heat is all of a sudden upon us! For most frog species, the heat is the ideal time to call and breed, when they have more energy and life is easier. A wetter than average spring has also helped things along.
The Bureau of Meteorology is predicting the La Niña conditions to last into the summer, which means higher than average levels of rainfall and good weather for frogs!
The tree frogs are beginning to call all over Victoria. But don’t be confused by the name, there are many species of tree frog that you are more likely to find on the ground than in the trees! It promises to be a good season for frogs in most habitats, so get your raincoat and gumboots on and have a wander in the rain, the frogs are calling you!
Project Coordinator, The Frogs Are Calling You
Southern Brown Tree Frog Litoria ewingii
Photo by Matt Clancy
Also known as: Brown Tree Frog, Whistling Tree Frog and Ewing’s Tree Frog
Distribution: Most of Victoria (not the north-west).
Conservation: Not considered threatened.
Habitat: Lots of places! Often found in gardens and suburban ponds, puddles, flooded grasslands, dams, lakes. It breeds in still waters, but adults can be found long distances from standing water.
Call: A whirring, almost soothing, fairly high-pitched pulsing call. They call mainly in spring and autumn, but may be heard at other times.
And another thing: Southern Brown Tree Frogs are also found in New Zealand where they are an invasive species (not native, introduced) and have continued to persist and spread.
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By Elaine Bayes, WetMAP field scientist
When you have camped out for 14 nights or so and mainly hear common species, it is a real thrill to go, ‘Did you hear that? What is that calling?’ Particularly if it is a species that mostly calls in winter and one you may not have heard for a couple of winters. This happened on a more adventurous frog survey a few weeks ago at Reedy Swamp near Shepparton. The call was of a species in the Whistling Frog group, which is composed of three species. Two of these sound and look very similar; the Plains Brown Tree Frog (Litoria paraewingi) and the Southern Brown Tree Frog (Litoria ewingii). [Check out the Featured Frog column for comparison – ed.].
This is where the amazing service of the Frog ID app comes in. Having tricky calls confirmed by an expert is a very handy tool, which we highly recommend before adding species to any of the current databases. So, having a few hours to kill while waiting on the RACV to come help us (we learned that you can over deflate your tyres while trying to get un-bogged!), I tried to get a really clear recording of the call with my Frog ID app. I waded out to the middle of the wetland and got as close as I could to what we believed to be Plains Brown Tree Frog calling from tall Juncus ingens (Giant Reed) in the centre of the wetland. Together with the recording and some great photographs by Damien, Frog ID confirmed the identification to the best of their current knowledge, but stated that in the future more research will be done on this group of frogs and the identification may be reassessed.
Another exciting find was the mostly winter-calling Sloane’s Froglet (Crinia sloanei) at the amazingly intact Doctors and Moodies Swamps. Both these sites had three Crinia species calling. These species are very similar looking, but we can tell them apart by their calls and some subtle differences like pattern on the bellies and the fact that Sloane’s Froglet has small orange-capped warts.
So fellow froggers, enjoy getting out to collect valuable data on your Frog ID app while this wet weather lasts. It will fill your soul with joy, and our databases with data.
Plains Brown Tree Frog, Litoria paraewingii by Damien Cook (Rakali Consulting)
Reedy Swamp, near Shepparton, Victoria, by Dan Purdey
By Rob Hale, WetMAP scientist Arthur Rylah Institute (ARI)
In the last issue, I wrote an article outlining how Geoff Brown (also from ARI) and I had spent several weeks analysing data collected from the WetMAP frog monitoring program during 2018-2020. Our results showed clear benefits of environmental watering for frogs, and that water quality and habitat are also important.
Since the last issue, we have been busy writing a technical report summarising our key findings and providing recommendations to catchment management authorities and the Department of the Environment Land, Water and Planning (DELWP) so that they can use the information to adapt the way they manage the flow of water for the environment. The report focuses not only on frogs but also vegetation, fish, and birds, which are being monitored as part of the wider WetMAP program. Collectively, our results provide a very detailed picture of the benefits of environmental watering for wetlands.
We reported that for both frogs and birds abundance (the number of individuals) and species richness (the number of species) were greater at watered sites. The same is possibly true for fish, but more data are required to confirm the significance of our findings. There was also more breeding activity in frogs, birds and fish at watered wetlands. Vegetation benefits too – we reported more plant material and more wetland species in watered wetlands.
The WetMAP team are now very busy planning for the next phase of the project. One of the ideas we are exploring is placing small devices (called “AudioMoths” – a very popular way to study wildlife, google for more info!) at wetlands to record frog calls that are then identified using computer programs. This is a fantastic way to collect very detailed information about frog calling and offers great promise as a tool to monitor responses to environmental watering in addition to data collected by scientists and citizen scientists.
What is a Wetland?
Dams, ponds, lakes, billabongs, swamps…
The term “wetland” refers to all of the above and more! Wetlands don’t have to be wet all the time to be considered wetlands. Wetlands don’t have to have standing water either – saturated ground also makes a wetland. Wetlands also don’t have to be fresh water – marine lagoons and inland saline wetlands can also count.
Some wetlands have trees growing in and around them and some wetlands may have no vegetation at all, or short, slow-growing vegetation. Man-made and natural waterbodies are both considered wetlands. Rivers and creeks are not normally considered wetlands in Victoria, but very slow-flowing waterways can sometimes count.
The Ramsar Convention on Wetlands is an international treaty on wetlands and it uses a broader definition that includes rivers. The Convention on Wetlands provides an international framework for the conservation and management of wetlands.
Gippsland Lakes Coastal Wetland RAMSAR listed significant site. Photo: RAMSAR Official site for Melbourne, Victoria, Australia
Wetlands are not just beautiful, providing support for biodiversity, they act as sediment traps and filter nutrients and pollutants, protecting the water that people drink. Around the world, wetlands support economies through tourism, food and recreation.
In Victoria, wetlands are an important part of Aboriginal cultural heritage and have provided food and livelihoods for people for thousands of years.
Even artificial ponds count as wetlands and have cultural and ecological value. Photo: Michael Coghlan
Find out more at:
Water, data, everywhere!
Want to create your own scientific project report? If you have collected lots of frog call recordings, you can probably have a go at collating your own WetMAP-style report! Follow the steps below to analyse your data.
1. Form a question or hypothesis. Good science always starts with a question you are trying to answer, or a hypothesis for which you are trying to find evidence. The more specific your question, the easier your analysis will be. A good question for a WetMAP-style study might be “Do more frog species call in my dam in spring?”
2. Have you got enough data? Generally speaking, the more data you’ve got the better. To find out if more frog species call in the spring, you’ll need repeated sampling, e.g. multiple recordings at the same location from different times of the year. The more data you have, the clearer your answer is likely to be.
3. Enter your data. If you’re computer-savvy, Microsoft Excel is an excellent place to start with statistics. But you don’t need to get fancy – good old-fashioned pencil and paper work well too! Make a table to enter your data into, like the one below.
4. Analyse your data. Straight away we can see by looking at the very basic descriptive statistics (e.g. total numbers, averages) that there is little difference in our dam between spring, summer and autumn, but that fewer species call from our dam in the winter. We can create a graph (either in a program like Excel or just on paper) to help visualise our results too (Fig 1).
5. We should also perform some inferential statistical tests to test for significance. Tests for statistical significance take into account things like the sample size, the differences between the descriptive statistics (and whether that’s likely to be true, based on how big those differences are) and the variation in the data. There’s not really space in one newsletter to explain all those wonderful statistical possibilities, but if you search the internet for “Inferential Statistics” there are lots of resources and ways to learn more.
6. Form a theory, reform your hypothesis, or ask another question. One of the best (and worst!) things about science is that one question always leads to more questions! In our example we could just leave it at what we have so far – the frogs in my dam call less in winter. Or we could ask more questions – maybe trying to find out why (“Do frogs call more when it is warm?”; “Do frogs call more when it is raining?) or maybe asking a similar question (“Do more frog species call in the warmer months?”). We could also just keep collecting data and see if we get any clearer patterns the more recordings we collect. But we probably have enough here to form a theory: “No more species of frogs call during the spring than the summer or autumn, but fewer species call in the winter”.
7. Write your report using all that you have found – make sure you include your question or hypothesis, your methods of data collection and analysis, your results and your theory and conclusions. Feel free to share them with us (email@example.com or on social media, @frogscalling or #frogscalling)! We’d love to know what you’ve found.
Find Out More
Environmental Water: www.vewh.vic.gov.au
The Frogs Are Calling You: www.frogscalling.org
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