Croak! Winter 2020
Updated: Aug 1, 2020
From the editor
Winter in Victoria is an amazing time for frogs! Just when you might think frogs are slowing down, some species are making the most of our wettest season.
If you’re in the west, you might hear Painted Burrowing Frogs (Neobatrachus sudelli) calling from puddles and ponds in the next month or two. For the rest of Victoria, the usual suspects are also happily singing away at the moment - Common Eastern Froglets (Crinia signifera) and Spotted Marsh Frogs (Limnodynastes tasmaniensis) continue to top the list of frogs most often heard.
So wrap up warm and keep recording – the frogs are calling you in the winter too!
Project Coordinator, The Frogs Are Calling You
Spotted Marsh Frog Limnodynastes tasmaniensis
Photo by Geoff Heard
Also known as: Spotted Grass Frog
Distribution: Throughout all Victoria.
Conservation: Not considered threatened.
Habitat: Permanent and semi-permanent wetlands – farm dams, lakes, flooded areas and swamps.
Call: Low-pitched, fast clucking. They call through most of the year.
And another thing: This species is the most recorded by citizen scientists in our target areas in northern and western Victoria.
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By Rob Hale, WetMAP scientist
Geoff Brown and I (both from the Arthur Rylah Institute - ARI) have spent the past few months analysing the data collected from the WetMAP frog monitoring during 2018-20.
We have found clear benefits of environmental watering for frogs. Significantly more frogs were counted (number of frog species, total number of frogs, and numbers of individuals of each species) at wetlands that received environmental water than at dry sites. In many cases, we observed as many or more frogs at wetlands that received environmental water than those that are permanently wet. We have also found that water quality and habitat (like vegetation along the edges of wetlands) are important for frogs.
The total number of frogs observed at WetMAP sites during 2019 audio-visual surveys.
D “Dry”: Wetlands that did not receive environmental water and were dry, n (sample size) = 5
NAT “Natural”: Wetlands that only received natural water (e.g. rainfall) and contained water, n = 1
PW “Previously Watered”: Wetlands that have received environmental water in the previous year and still contained water, n = 3
W “Watered”: Wetlands that received environmental water in the spring, n = 9
PER “Permanently Wet”: Wetlands that always contain water and sometimes get topped up with environmental water, n = 4
The bold horizontal lines mark the median (middle) number of frogs we counted. The boxes around them show the amount of variation in our results as the (interquartile range: 25th to 75th percentile). For example, dry sites never had any frogs, but watered sites often had between 25 and 80 frogs depending on the visit. The vertical tails show the extremes of the data (values greater than 1.5 x interquartile range), and the black dot shows a value outside these extremes.
We are also starting to explore the relationship between frogs and the longer-term hydrological regime. While individual inundation events are important, understanding longer-term fluctuations is critical to managing wetlands. Our results so far show that different species respond differently to changes in wetland hydrology. For instance, we found:
more Eastern Sign-Bearing Froglets (Crinia parinsignifera) when wetlands contained water for more of the previous 30 days,
more Eastern Banjo Frogs (Limnodynastes dumerilii – also known as “Pobblebonk”) in wetlands with a higher proportion with water in the previous 90 days.
This could be because the tadpoles of the Eastern Sign-Bearing Froglet develop faster than those of the Eastern Banjo Frog. This sort of information can help us determine how much environmental water needs to be released so that wetlands have water in them when the frogs need it to breed.
We are preparing a technical report summarising our key findings for catchment management authorities and DELWP to help inform how future environmental flows can be managed most effectively.
By Elaine Bayes, WetMAP field scientist
The autumn/winter 2020 WetMAP frog surveys have just been completed. We carried out surveys in three wetlands in the North Central catchment and seven in the Goulburn-Broken catchment, following environmental watering in autumn/winter.
It was a tad on the cold side (for us, not the frogs!) and my partner Damien Cook and I camped out at the wetlands for around two weeks. The night time survey temperatures were between 9-11°, but the rewards were worth the chilly fingers. Crisp, clear night skies and a feeling of awe as we stood quietly on the edge of the wetland, torches off, listening to the frog calls piercing the sharp air.
As well as environmental water, many sites had a helping hand from autumn and winter rains. Doctors Swamp in Murchison looked stunning, as run-off from substantial rain had stimulated the growth of abundant aquatic plants and aquatic food webs were kicked into action by the addition of water and nutrients.
Doctors Swamp and Moodies Swamp, which are two of the most ecologically and hydrologically (flooding/drying regime) intact wetlands in the region, had the most frog species this season, with 4 and 5 species present respectively.
Seven species of frog were detected during the May to July 2020 surveys, some of which were different to those heard or seen during summer surveys.
Different frog species call at different times of year, so as well as the common species which we hear all year round, we were excited to see and hear the Painted Burrowing Frog (Neobatrachus sudelli), a particularly photogenic species (if a bit comical looking) that is usually buried in the soil but emerges after rain events. If you look closely, they actually have a spade-like structure on the hind foot for digging!
The black “spade” of a Painted Burrowing Frog Neobatrachus sudelli
(also known as the Spadefoot Frog).
Painted Burrowing Frog Neobatrachus sudelli
So rug up and happy frogging. ‘Til next time when we will be raving about the heat and the mossies!
Carol from Murrindindi Shire has been collecting data for The Frogs Are Calling You since April 2020.
Why did you join The Frogs Are Calling You?
I had been contributing to the Frog ID project for about six months and I was searching for more information on frogs and up popped “The Frogs Are Calling You” website. I thought it would be good to share the information I was already collecting with an organisation that was focused on my local area.
What do you do when you’re not recording frog calls?
My husband and I are both retired and love to spend time in the Australian bush - travelling, bushwalking, camping, kayaking and birdwatching. We walk for an hour most days along the rail trail and country lanes in our area and that is a great opportunity to hear and record frog calls, as well as do other surveys.
Have you done any citizen science before?
Yes, for many years I have been contributing bird surveys to BirdData and eBird. More recently, I have joined citizen science projects such as Wild Orchid Watch, Butterflies Australia and the Fairywren Project.
Are you a frog expert?
No, I am definitely not a frog expert, but it is amazing how quickly you learn about the frogs in your local area.
Where do you collect frog calls?
I collect frog calls from all around my local area. I’m regularly out and about walking trails in the district and whenever I hear a frog calling, I whip out my mobile phone and make a recording. It makes my walks much more interesting.
Have you learnt anything from the project?
I have learnt heaps from the project! I can now identify most of the frogs in my local area and am much more attuned to frog calls wherever I go. I love the fact that the Frog ID staff give you feedback on the calls you submit, and their encouraging comments really help to keep me motivated. In general, I think all citizen science projects make you much more aware of the world around you and that has to be a good thing.
Frogs and Environmental Water: The Story So Far
The flow of water in dry areas of Australia has always been very variable. Because water levels need to be relatively consistent for people to use for agriculture and industry, many of Australia’s rivers have become modified with infrastructure such as weirs to regulate flows. As a result, some wetlands that used to dry out regularly now do not and some wetlands that used to be regularly filled by flood waters do not or get less water than before.
Water for the environment, or ‘environmental water', is water that is released into rivers and wetlands to sustain and improve the condition of waterways and wildlife. Environmental water is used to fill wetlands that are running dry and to top up wetlands that would naturally contain more water. Environmental water is being used to make flow regimes more natural and better suited to the wildlife that rely on wetlands.
Frogs have been in Australia for millions of years and their breeding cycles have adapted to the natural water cycle. Despite having been around so long, frogs are quite fussy when it comes to breeding! They are limited by temperature (because they are cold-blooded) and because they have sensitive amphibian skin (through which they absorb oxygen) they are dependent on moisture. Most species of frogs need water-bodies in which to breed. Changing the way water behaves in the ecosystem can significantly impact frogs and their reproduction.
Because frogs are so sensitive to changes in water and are so important as components of the ecosystem, how they react to environmental watering is vital information for water managers. But it’s not as simple as more water means more frogs! Although they do need water, sometimes less is more. Wetlands that dry out periodically often have fewer predators (like fish) than permanently wet ponds. The vegetation that grows around ephemeral pools is also different and potentially better for frogs. The water also needs to stay in the wetland for the whole of the breeding period and for as long as it takes for the tadpoles to metamorphose and be able to live on land. Each species also differs in its requirements for timing and duration of breeding as well as specific habitat and weather requirements. On top of that, because of the complex combination of all the different factors, there are often differences between each individual wetland.
A study by Emily Hoffman, from South Australia’s Department of Environment, Water and Natural Resources, showed that the delivery of environmental water to dry temporary wetlands triggers frogs to breed. What’s more, it seems as though there were more frog species and greater abundance (higher numbers of individuals) of tadpoles at dry wetlands that received environmental water than at permanent wetlands. A Wassens and Maher study examining frog ecology in relation to inland creeks with weir systems found that temporary pools were more likely to contain rarer species than permanent pools, but that the temporary pools had to contain water for long enough for tadpoles to metamorphose and move out. A team of scientists led by CSIRO’s Heather McGinness investigated how flooding and habitat influenced frog diversity (number of species) and abundance (number of individuals) in Barmah Forest. They found that the males of each species called at slightly different times of the year (although there was some overlap) and only some of the species seemed to do better in wetter years. They concluded that although frogs definitely benefited from water, each species seemed to do so differently.
This all suggests that environmental water is extremely important for frogs, but we need to know a lot more about how and why. Because water is getting scarce and more valuable as our climate warms and dries, it is vital that we understand as best we can what frogs need and when. There is still lots to learn about the requirements for each frog species at different wetlands across Victoria. That’s where WetMAP and citizen scientists come in, to investigate how frogs respond to watering regimes to help inform water management.
Margooya Lagoon (near Robinvale in north west Victoria), a wetland that receives environmental water
Find Out More
Environmental Water: www.vewh.vic.gov.au
The Frogs Are Calling You: www.frogscalling.org
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