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Follow that frog in the Lachlan valley - August 2016

When the creeks run dry and the temperature rises, where do all the frogs go?

Amphibians are among the first animals to respond when water arrives in a wetland. Their croaking chorus creates a din that can be heard kilometres away. But how do inland frogs survive Australia's hot dry summers when running water can all but disappear?

Carmen measuring a tiny frog on a white plastic ruler

Carmen Amos in her role as environmental scientist with OEH

Scientists have had their theories, but until now, solid evidence has been hard to come by. It's this lack of formal information that prompted environmental scientist Carmen Amos to dig a little deeper.

Carmen works for the Office of Environment and Heritage evaluating the effects of watering on wetlands, creeks and rivers in the Lachlan and Murrumbidgee valleys. At the same time, she is finalising her PhD through Charles Sturt University's School of Environmental Science on the impact of environmental factors on frog communities in the Lachlan valley.

As part of her PhD, Carmen has assessed 49 sites across the valley to determine which factors encourage frogs to occupy a particular location. She has listened to hours of frog recordings in an effort to identify the factors that may encourage frogs to call when their habitat is already wet. And she has spent many long, dark nights on the trail of these elusive amphibians in a bid to understand their preferred hideouts when water is scarce.

Carmen's methods are 'colourful' and provide a valuable insight into the survival strategies of frogs in semi-arid Australia.

'I've always loved frogs but there are so many unanswered questions, particularly when it comes to frogs in arid and semi-arid environments,' Carmen said.

'How long will frogs stay in a drying wetland before they move? How far can they move between permanent habitats? Can young frogs move long distances?

'In the course of my work, I've seen frogs crawling out of cracks in the dirt, but there isn't a lot of literature to support the observation. So, as part of my PhD, I decided to tackle of the idea of where frogs go during the day to shelter from drying conditions.

'My focus was on terrestrial microhabitat - places on land where the frogs might seek shelter during the heat of the day. The habitat types included deep soil cracks and holes, vegetation and coarse woody debris.

'I chose six sites, each with a variety of potential terrestrial habitats within close proximity of one another. Water had been delivered to these sites within the past year so the soil was wet but in the process of drying down.

'I focused on the spotted marsh frog because it is relatively common and present at each of the sites.

'On four separate occasions, I visited each site and captured up to 10 spotted marsh frogs by hand. Each frog was weighed, measured and dusted with a pink fluorescent powder. The frog was then returned to the spot where it had been captured for release.

'Early the following evening my research assistant and I returned to the release sites and used black light torches to follow the fluorescent paths left by each frog to their hot-weather hideouts.

'My research showed that spotted marsh frogs use mainly deep soil cracks and holes as their daytime micro-habitat. In terms of temperature, these microhabitats sit at around 25 degrees Celsius with humidity between 50 and 60 per cent - so, not too dry and not too wet.

'Two thirds of the frogs surveyed chose cracks and holes to retreat to during the day. This is interesting because when you look at the ground surface, those cracks and holes make up only one per cent of the visible surface microhabitat available.

'Potentially, there is a large and complex labyrinth of deep soil cracks below the surface, but that's a theory for a future study.

'Most of the frogs that formed part of the research were found using sub-soil habitat within 10 metres of the wetland but one was found 30 metres away. For a frog that measures just 4.5 centimetres in length, that's a long way.

'The frogs may have chosen this habitat because the evaporation of soil moisture decreases the deeper you go.

'This provides a cooler, moist environment that offers some protection to the frog during drying weather conditions,' Carmen said.

This research has the potential to influence future deliveries of water to rivers, creeks and wetlands that dry down during warmer weather.

'By understanding how these frogs use the terrestrial habitat surrounding wetlands, water managers can make decisions which provide the best opportunities for frog survival,' Carmen said.

'This may influence the frequency or duration of watering and the rate at which these wetlands are allowed to dry down. This research is best applied when conditions within the environment might be very dry and there is not a lot of environmental water available.

If we have a greater understanding of the conditions frogs need in order to shelter from drying weather conditions then available water can be applied strategically to promote these sort of environments.

'This may not lead to breeding, but will help support frogs during drier times, she said.

For environmental water managers, Carmen's research reinforces the need for both wet and dry phases within the wetland environment. Her findings may also influence decisions which help maximise the cost effectiveness of environmental flows.

Senior environmental water manager in the Lachlan valley, Paul Packard, said increased knowledge could help to decide the timing, duration and frequency of watering events.

'By identifying the needs and drivers of particular species and landscapes, we can target water more effectively and in concert with other sources of water in the system to achieve the best possible outcomes,' Mr Packard said.

'Carmen's research reinforces the importance of soil cracks as frog habitat and the understanding that we don't need to provide non-stop inundation to ensure the survival of these frogs.

'By using water efficiently we can provide sufficient habitat to allow frogs to rebound after a dry spell when more water becomes available,' he said.

Frog in mud

Frog in micro habitat. Photo: C Amos, OEH

Frog lit up with blues and purples

Black light frog detection. Photo: C Amos, OEH

Waterbirds flocks to Great Cumbung Swamp - January 2016

Waterbirds have flocked to the Great Cumbung Swamp in western NSW in response to environmental water.

The swamp has provided an oasis for at least 14 varieties of waterbird seen feeding and breeding at the site since water arrived late last year.

The Great Cumbung Swamp takes in some 20,000 hectares north east of Balranald.

It's made up of a mosaic of wetland types including reed bed swamps, river red gum woodlands, intermittent freshwater lakes, permanent freshwater ponds, marshes and more.

Water flows into the swamp via the Lachlan River. This water is shallow and spreads widely. It's absorbed by wetland plants, evaporates or re-charges the water table.

It is only during floods or extended wet periods that water flows right through the swamp and reconnects the system to the Murrumbidgee River.

Senior Environmental Water Manager Paul Packard said the swamp and river channel provided refuge for plants and animals during dry spells.

'The Great Cumbung Swamp is listed on the Directory of Important Wetlands because it contains one of the largest remnant examples of Common Reed (Phragmites australis) swamps,' Mr Packard said.

'More than 131 species of bird have been recorded at these swamps and lakes along with 207 plant species including 120 varieties of water plant.

'Last year 45,000 megalitres of environmental water was released into the Lachlan River, a large portion of which reached the swamp.

'Rainfall also contributed to the flow, providing a much-needed drink to 9,000 hectares of the Great Cumbung Swamp,' he said.

Other bird species making the most of this recent flow include straw-necked ibis, yellow spoon bills, cormorants and stilts.

'Even as the swamp dries out, it provides extensive areas of muddy shoreline where wading waterbirds can forage and frolic,' Mr Packard said.

Fresh for Spring in Lachlan River

Native fish in the Lachlan River will benefit from environmental watering this month.

A total of 20,000 megalitres of environmental water is being delivered into a 500 kilometre stretch of the river between Booligal and the Great Cumbung Swamp.

The NSW Office of Environment and Heritage has contributed 5,000 megalitres of environmental water while the Commonwealth Environmental Water Holder has provided a further 15,000 megalitres, to be delivered over a 45 day period.

Water NSW is managing the release of the water on behalf of OEH and the Commonwealth.

Commonwealth Environmental Water Holder David Papps said this event would improve connections between different parts of the river, swamp and floodplain, building on the benefits of inundation that occurred in 2013.

'We’re particularly keen to see the ongoing recovery and resilience of the Great Cumbung Swamp, which is why we’re using this environmental water to support the survival and growth of wetland vegetation such as reed beds, lignum shrublands and river red gums,' Mr Papps said.

'This flow will also support habitat for waterbirds such as straw-necked ibis, glossy ibis, egrets and other water dependent species.

'This watering event is also expected to provide drought refuge for waterbirds and other water dependent species should dry conditions continue,' Mr Papps said.

Senior Environmental Water Management Officer Paul Packard said tributary inflows higher up in the catchment had made the event possible.

'Water from tributary inflows is generally richer in nutrients than water released from the dams,' Mr Packard said.

'So, while we had planned for this event using dam water, the use of nutrient-rich water from inflows will provide even more benefits to the system.

'These nutrients feed the food web from a microscopic level up.

'When spring arrives, the ecosystem will be healthier and ready to support native fish, frogs and turtles as they become active,' Mr Packard said.

It is not expected that the flow itself will trigger fish breeding in either native fish or carp.

'If we watered when the weather was warmer, carp would breed quickly and get a head start on the available food resources,' Mr Packard said.

'By watering in winter when the water is cold, carp are not encouraged to move or breed, so when spring arrives it’s a more even playing field for the native fish.'

The flow will mimic a natural event with an early in-stream peak followed by a steady release over 35 days and a slow recession phase to minimise the risk of bank slumping.

'By watering at this time of year, we’re not competing with other river users for channel capacity, so this flow of 500 megalitres per day (at the flow’s peak) will stay within the river bank,' he said.

When the water reaches the bottom of the system it will spread through the Great Cumbung Swamp, topping up around 600 hectares of open water bodies and replenishing water levels in the reed beds totalling about 3500 hectares.

This environmental watering event is a collaborative effort between the Commonwealth Environmental Water Holder, the NSW Office of Environment and Heritage, WaterNSW, DPI Fisheries, local LLS, landholders and community members.

Water rats return to Lachlan valley

Water rat on a log at Burrawang.

A water rat at Burrawang, near Condoblin.

Its a native animal with an image crisis.

The water rat – an Australian mammal – is often mistaken for its introduced cousins, the black rat and brown rat.

But the water rat behaves more like an otter and has a positive and important role to play in the floodplain ecosystem.

At Burrawang, near Condobolin, there are increasing signs of water rat activity and sightings of the water rats themselves.

Senior Wetlands and River Conservation Officer Paul Packard said the discovery was good news for the region.

'The presence of water rats is a good indicator of ecosystem health,' Mr Packard said.

'It means that the food web is rebuilding and able to support the higher order predators.'

A series of environmental watering events assisted the return of the water rats. The latest occurred over winter/spring with 250 megalitres delivered to the lagoon on the mid-Lachlan to maintain refuge values and restore ecosystem health.

'We had seen evidence of old abandoned nests, but no live water rats,' Mr Packard said.

'That has now changed with the animals returning to the banks of the mid-Lachlan to nest and feed.

'The water rat is an opportunistic carnivore and eats a range of foods including freshwater mussels, yabbies, fish and worms.

'Environmental water has allowed us to restore the habitat and the food web these mammals require to thrive,' he said.

Water rat profile:

The water rat (Hydromys chrysogaster) is also known by its indigenous name – rakali. It is a member of the Muridae family, in the genus Hydromys.

It is one of only two amphibious mammals native to Australia – the other is the platypus. The water rat forages along the shore and underwater and builds its burrow along the river bank.

They were once common in Australia but their population declined as a result of altered flow regimes, hunting, loss of habitat and predation.

Mature water rats are markedly larger than introduced black and brown rats and can be distinguished by their partially webbed hind feet, thick white-tipped tail, small ears and blunt nose.

The sound of success

It was the sound researchers had waited years to hear - the 'waaah, waaah, rah, rah, rah' of the Southern Bell Frog.

The endangered amphibian was heard calling at 'The Ville', a property 5kms from Corrong, on the Lower Lachlan River, in October 2013.

Environmental flows had triggered the remarkable response.

While not seen, researchers were able to record the distinctive call, providing proof that the frog had returned.

Senior Wetlands and River Conservation Officer Paul Packard said the discovery was tremendously exciting.

'This response reinforces the theory that with careful and well-planned use of environmental water we can assist the recovery of this population,' Mr Packard said.

'With the big floods of 2012 the Southern Bell Frog was detected in Lake Bullogal – a lake that had been dry for more than 20 years.

'Before that, they hadn't been seen or heard in the Lachlan catchment since 1978.

'In an effort to consolidate the positive effects of the 2012 floods, an environmental flow of 90,000 megalitres was released into the Lower Lachlan River over the winter of 2013.

'As a result of this flow, the frogs were heard calling at "The Ville" soon after,' he said.

The Southern Bell Frog is relatively long-lived – about four years – but can't live or breed without water. It's thought that the frogs survived unnoticed for many years in farm dams and billabongs in the Lachlan catchment.

The OEH has funded researchers from Charles Sturt University to undertake surveys to establish the range and number of frogs present.

'We plan to repeat our monitoring and conduct specific, event-based surveys when applying environmental water in the area,' Mr Packard said.

'We are also going to continue our efforts searching for the Southern Bell Frog in other areas of the catchment using audio recording equipment to capture their calls.

'There are dozens of similar billabongs that could provide ideal habitat for the Southern Bell Frog.

'With further environmental flows we may be able to encourage existing populations to recover and repopulate the catchment,' he said.

Community role

The Lachlan community continues to play an important role in the recovery of the Southern Bell Frog.

'The excitement and enthusiasm of the Lachlan catchment community is one of our greatest resources,' he said.

'Landholders are in an ideal position to provide valuable intelligence on the presence of the Southern Bell Frog on their properties and we are keen to hear from anyone who thinks they may have Southern Bell Frogs on their land,' Mr Packard said.

About the Southern Bell Frog

The Southern Bell Frog (Litoria raniformis) is classed as endangered in NSW and vulnerable nationally.

The frog is one of the largest species in Australia reaching up to 104mm in length.

Their colouring ranges from bright green to dull olive with brown or golden marbling. The back is warty with a pale green stripe down the middle. The groin and thighs are usually blue with or without a few small pale yellow spots.

The frogs are generally found in vegetation along the edges of permanent or semi-permanent water. They are most active at night, especially on warm nights, after rain when they are more likely to be heard calling.

The Southern Bell Frog feeds on a range of insects, water snails, small fish, tadpoles and other frogs (even juvenile members of the same species).

Their tadpoles grow to about 10 centimetres long, and take anywhere from two months to one-and-a-half years to fully develop.

Follow that sound! Office of Environment and Heritage staff are on the trail of endangered Southern Bell Frogs heard calling in the Lachlan valley. Their re-emergence after environmental watering is a positive indicator of the catchment’s health.

Recording © David Stewart Nature Sound by David Stewart

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Page last updated: 11 August 2016