Frogs > Main’s Frog | sheep and tadpoles

Did you know that the mating calls of the male Main’s Frogs sound like the bleating of sheep, hence its other more common name of ‘Sheep Frog’. The call they make is to attract the female.

Main’s Frog (Cyclorana maini), Palm Valley, NT
Main’s Frog (Cyclorana maini), Palm Valley, NT

Grouped together with other burrowing frogs, it survives the dry periods by absorbing water into its body, burrowing deep underground, and encasing itself in a watertight bag (cocoon), awaiting the next major rain fall.

At the onset of aestivation, these frogs assume a ‘water-conserving’ posture and become inactive. A thin, transparent cocoon is observed to form within a week of onset of inactivity, and becomes progressively thicker and more opaque. The cocoon covers the entire body surface, including mouth, eyes and cloaca, except for the narial openings.1

Cocoon Formation and Structure in the Estivating Australian Desert Frogs, Neobatrachus and Cyclorana,

This water-holding frog has adapted to desert conditions, living in some of the harshest country in the arid region of Western and Central Australia. Under favourable wet and rainy conditions, they can usually be found in temporary pools in watercourses, claypans and other short-lived bodies of water. They are also found in habitat that include open grassland, lightly forested areas and temporary marshes and streambeds in temporary flood plains.

The frog is named after Professor Bert Main of the University of Western Australia, a pioneer of southern Western Australia frogs.2

The mating call of the male ‘Sheep Frogs’ can be particularly loud, especially when there are a number of the same species bleating out loud in chorus.

Call of the Main’s Frog (Cyclorana maini) at Alice Springs Desert Park, NT

More sound files for the call of the Main’s Frog can be found online, including:
Cyclorana maini, Australian Museum FrogID Project, includes sound files.

Once they mate, the female lays the eggs into the available pools of water.

Whilst in some parts of Australia it is common that frogs breed in late spring to early summer, there is no hard and fast rules, as many frogs species are opportunistic breeders, especially in arid regions such as Central Australia, where they emerge to breed after any significant rainfall.

Once the tadpoles develop from the eggs, they tend to hide from predators in the mud at the bottom of the water, coming to the surface for air.

Tadpole metamorphosis, Finke Gorge National Park
Tadpole metamorphosis, Finke Gorge National Park

The actual metamorphosis from egg to tadpole to frog can vary widely, taking two to three months, although under certain circumstances, the time frame is shorter. Some desert frog species can take as little as 16 days to become frogs.

There appears to be two factors that trigger metamorphosis, a rise in temperature and or a lack of food. A simple rise in temperature can trigger the change in many species. Also, a lack of food can be a major motivator. As the tadpole’s food supply runs out, the quicker the tadpoles can change into frogs will enable them to find more food.

If has been documented that some environmental situations, such as the tadpoles living in a small amounts of water, which would naturally heat to higher temperatures, is known to trigger the tadpoles to develop at a faster rate, developing into adults frogs within 14 days.

This seemingly hurried lifecycle from egg to tadpole to adult frogs is a common feature of frogs from the arid and desert region, as water when it does fall is usually only around for a brief period. Nowhere is it more evident then seeing a former pool of water, drying out, still filled with tadpoles that did not grow quick enough to complete their lifecycle.

The tadpoles of the Main’s Frog are fairly large, varying in colour from orange-gold, copper pink over a grey base, dense grey-gold or dull gold with dark speckling. In the following image of the Main’s Frog (Cyclorana maini), you can see just the back legs starting to grow.

Tadpoles metamorphosis, Finke Gorge National Park
Tadpoles of the Main’s Frog (Cyclorana maini) with the beginning of metamorphosis

If the tadpoles are unlucky, the eggs having been laid in shallow depressions, or pools where evaporation is quick, if the they do not metamorphosis quickly, they will perish. It could have been just the wrong pool of water, overcrowding, insufficient food or the strength of the midday sun that saw the demise of these tadpoles.

Human nature being what it is, sometimes it was too much to see all the dead tadpoles desiccating in the dry rock pools. When we saw one such small rock pool with a concentration of tadpoles that would have surely perished, we decided to rescue them and release them into the nearby main waterhole, just metres away.

In the adult Main’s Frog (Cyclorana maini) frog, its skin may vary from pale grey-brown, olive-brown, dull green on its back, with darker patches. The back is smooth or slightly rough or warty in appearance. Look for the distinct pale stripe that runs along the spine. There is often a dark lateral head stripe.

Main's Frog (Cyclorana maini) at Uluru
Main’s Frog (Cyclorana maini) at Uluru-Kata Tjuta National Park

  • Scientific classification
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Amphibia
  • Subclass: Lissamphibia
  • Order: Anura
  • Family: Hylidae
  • Species: C. maini
  • Binomial name: Cyclorana maini

Footnote & References

  1. Cocoon Formation and Structure in the Estivating Australian Desert Frogs, Neobatrachus and Cyclorana, CSIRO Publishing, Australian Journal of Zoology, Retrieved September 9, 2008, from http://www.publish.csiro.au/paper/ZO9950429.htm
  2. Everything You Ever Wanted to Know About Frog Sex (but Were Afraid to Ask), JSTOR Daily, https://daily.jstor.org/everything-you-ever-wanted-to-know-about-frog-sex-but-were-afraid-to-ask/#:~:text=In%20the%20most%20common%20method,hours%2C%20days%2C%20even%20months.
  3. Tadpoles on the hop, by Paul Willis, 1 March 2001, ABC Science, https://www.abc.net.au/science/articles/2001/03/01/2634058.htm#:~:text=The%20metamorphosis%20from%20tadpole%20to,time%20it%20takes%20varies%20widely.
  4. Cyclorana maini, Australian Museum FrogID Project, includes sound files, https://www.frogid.net.au/frogs/cyclorana-maini