What do you call an animal that has sharp teeth, is olive to emerald green in colour, has a creamy white belly, with brown, black or bronze warts on its back and a pale green stripe down the middle? An animal that can lay as many as 4,500 eggs in one breeding season and when it growls sounds like a duck with hairball stuck in its throat? A Growling Grass Frog of course!
One of the largest frogs in Australia, this fascinating amphibian can grow up to 14cm long; the young tadpoles themselves sometimes measuring up to 10cm before they metamorphose into adult frogs. Predominantly found in still or slow moving wetland systems such as lagoons, swamps, lakes and ponds with grassland habitat and emergent vegetation, the Growling Grass Frog relies on its environment for food, shelter, breeding and egg-laying.
Breeding occurs between November and March, the season triggered by local flooding and a significant rise in water levels due to increased rainfall. Tadpoles generally hatch within 2–4 days of the eggs being laid, and metamorphosis usually takes up to 3 months to complete.
Once distributed widely across areas of south-eastern Australia, in New South Wales and the Australian Capital Territory, Victoria, South Australia and Tasmania, over the past ten years there has been an estimated 50% decline in Growling Grass Frog numbers. The species is now only found in small, isolated populations across these sites, with this drastic reduction due to a number of threatening processes, such as the chytrid fungus disease, loss and degradation of habitat, water pollutants and predation by introduced fish species. Werribee Open Range Zoo is home to one of the few existing wild populations of Growling Grass Frogs.
Although still widespread in New Zealand, where this frog species was introduced in the 1800s, the Growling Grass Frog is classified as Endangered according to the International Union for Conservation of Nature and Natural Resources (on the IUCN red list) due to their declining population and increasing threats.
You can see Growling Grass Frogs in the Bandicoot Hideout at Werribee Open Range Zoo.