Australian Frogs
With 216 frog species currently described and new species still being discovered, Australia is classed as a significant centre of amphibian diversity. With Australia’s long isolation from other countries, this means that 200 of these species are found only in Australia. This means that any loss of these species in Australia means the loss of the species worldwide.
Australia has three main native frog families; Myobatrachidae (ground frogs), Hylidae (tree frogs), and the tropical Microhylidae.
Australia has the 18th greatest number of threatened amphibians worldwide, with 47 species of Australian frog are classified as vulnerable, endangered or critically endangered (IUCN Red List). In the 1980s it was discovered that two unique Australian species, the Southern Day Frog (Taudactylus diurnus) and the Southern Gastric Brooding Frog (Rheobatrachus silus) had disappeared from their entire range. The cause for their apparent extinction could not be identified.
While the reasons for many local losses of frogs can be put down to specific causes, the decline and disappearance of frogs in Australia and other continents from relatively undisturbed habitats indicates direct human activities are not solely responsible for all declines. Indirect threats such as climate change, which are the summation of long-term human activities, may also play a large role in threatening frog populations.
South Australian Frogs
FAMILY HYLIDAE
In South Australia, there are only two genera in the family Hylidae - Cyclorana and Litoria:
Cyclorana species are burrowing frogs that are commonly called water holding frogs because of the large amounts of water they store. They do not possess toe discs but have a metatarsal tubercle, a hardened ridge on the undersurface of the foot, which acts like a spade to assist in digging. In most species, there is very little, if any, webbing between the toes.
Litoria species are predominantly tree frogs that have flattened discs on the tips of their fingers and toes that secrete sticky mucus to aid in climbing. The undersurface of the disc has an indentation around the circumference. Most Litoria species have long legs and large amounts of webbing between the toes, while the fingers may have small amounts of webbing.
All South Australian hylids lay clumps of eggs in the water.
FAMILY LEPTODACTYLIDAE
The vast majority of frogs in South Australia are in the family Leptodactylidae (also known as Myobatrachidae), of which there are six genera in South Australia (Crinia, Geocrinia, Limnodynastes, Neobatrachus, Pseudophryne and Uperoleia). They range in size from about 1.3 cm (Crinia deserticola) to 8.3 cm (Limnodynastes dumerili). These frogs have a very diverse range of habitats, lifestyles, body forms and reproductive strategies. Most are terrestrial, but they occupy a wide range of habitats from wet areas around streams and swamps to desert regions that have very little water.
There are varied reproductive strategies used, even within a genus. Some lay eggs in clumps attached to submerged vegetation, others produce a floating foam nest, long chains of eggs or have semi-direct development within the egg capsule laid on land.