The fight to save the growling Grass Frog at Wirra-lo

The Growling Grass Frog (Litoria raniformis) is one of the largest frog species in Victoria, growing up to 10 cm long. They are often bright green with golden and black blotches and have deep growling call that has been compared to a revving motorbike. They are carnivorous and will eat almost any animal smaller than themselves.

The Growling Grass Frogs was once extremely abundant across south-eastern Australia, and historical accounts from several areas including around Melbourne describe them as being “the most common species of frog”. From around the 1980’s Growing Grass Frog populations declined dramatically, and the species is now listed as vulnerable to extinction both in Victoria and nationwide.

What caused a species that was historically widespread and abundant to become so rare? Like many endangered species, it was a combination of factors including the destruction of wetlands, disease, the use of toxic chemicals including herbicides and insecticides and introduced predators such as feral cats and foxes.

The introduced chytrid fungus is believed to have played a major role in the decline of Growling Grass Frog populations. This disease attacks the frogs skin and has caused the localised extinction of populations in cool, moist regions. Interestingly the fungus doesn’t survive well in hot conditions, and it is believed frogs can reduce the severity of chytrid infection by basking in the sun. One of the strongholds of the Growling Grass Frog in Victoria is the northwest of the state, where the hot, dry summers probably reduce the spread and severity of chytrid fungus infections.

The Kerang region is on the edge of the semi-arid northwest of Victoria and until about the year 2000 quite a number of Growling Grass Frog populations were known from this area. The millennium drought which occurred from 2000 until 2010 seems to have had a major impact on these populations however, and there have been very few Growling Grass Frogs observed in the region since 2010.

Wirra-lo Is a private property covered by a conservation covenant at Murrabit West, north of Kerang, that supports 11 wetlands. Jill and Ken Hooper, the current owners of Wirra-lo, remember hearing Growling Grass Frogs throughout their wetlands until the Millennium Drought. In 2007, at the peak of the drought all of their wetlands had dried up and the Growling Grass Frogs fell silent.

Jill and Ken noticed that the frogs weren’t the only wildlife affected by the drought; it was also having an impact on many other species including the two families of endangered Grey-crowned Babblers that lived at Wirra-lo. Jill and Ken resolved to turn Wirra-lo into a drought refuge and haven for wildlife and being irrigation farmers new how to get water to their stricken wetlands.

They approached the North Central Catchment Management Authority and the Victorian Environmental Water Holder, who formed a partnership with them to help change the irrigation infrastructure at Wirra-lo from a system that irrigated paddocks for growing pasture into a system for getting water into the wetlands in 2015. Wirra-lo was the first private property to receive environmental water in Victoria.

Before the water was delivered wetland ecologist Damien Cook worked with the Hoopers to design a restoration project for Brolga Swamp on Wirra-lo and when the first water flowed in local Barapa Barapa Traditional Owners were employed to help plant 2000 indigenous plants representing 30 species.

Some indigenous wetland plant species regenerated from seed that had survived in the soil and these and the planted species flourished together to cover Brolga Swamp with a lush cover of wetland plants that formed excellent habitat for wetland birds and frogs.

On a warm spring evening in 2017 Damien was weeding on the edge of Brogla Swamp when he heard a noise that nearly made him jump out of his skin; two male Growling Grass Frogs singing at the other end of the wetland.

After a lot of clever design and hard work all 11 wetlands at Wirra-lo can now receive flows of environmental water provided by the Victorian Environmental Water Holder or the Murray Darling Wetland Working Group.

Regular surveys have shown that the number of Growling Grass Frogs at Wirra-lo is growing steadily and with careful restoration and management Wirra-lo is fast becoming the wildlife haven that Jill and Ken had the vision for.

The Wetland Revival Trust is purchasing Wirra-lo from Ken and Jill to carry their vision into the future to make sure that the Growling Grass Frog, Australasian Bittern, Grey-crowned Babbler and other indigenous animals and plants continue to thrive at Wirra-lo.

Category: Miscellaneous