Blue frogs
  • Last updated:
  • 21 Nov 2019

A couple of weeks ago I couldn’t get my foot into my left safety boot that had been kept on a shelf on the back verandah. I thought I must have left a sock in it but no, it was a Green Tree Frog that had commandeered the boot as a safe day-time hide-out. It would appear that he didn’t mind a bit of foot-odour.

At night we often observed him out foraging and without fail every morning he would return curiously, alternating between right and left boot of the pair of boots. Friends warned us that frogs were not easy to house/boot train and there would be a mess but this frog was very fastidious about house-keeping. For nearly four weeks I was deprived of the use of that footwear but then one morning he was missing.

Just near that shelf we have a frog home, a setup of pipes providing shelter and moisture, and at any time it has an occupancy rate of up to four frogs; perhaps that is his new place. We always name our critters, so he is Jack(boot) and the two constant occupants of frog home are the Brothers Grin because of their silly wide smiles.

Green Tree Frogs are one of Australia’s most recognised and loved species of wildlife, found over all of Queensland and New South Wales, the Northern Territory (except for inner desert regions) and the northern part of Western Australia. They are also the most domesticated of our frogs, seeming to prefer living in close proximity to us, inhabiting our gutters, hanging flowerpots, toilets and our boots. They are also a popular, long-lived and easy-care pet.

The scientific name of the Green Tree Frog, Litoria caerulea, has historical and technical meanings. Litoria refers to the coastal or littoral zone and was coined by Swiss herpetologist Tschudi in 1838. The word caerulea means sky-blue. These frogs are obviously green, sometimes with a few white spots and sometimes olive-brown, depending on their mood and surrounds. But they are definitely not blue.

Early specimens sent back to England

This is the first frog species collected in Australia (by Sir Joseph Banks) and was first described 20 years later in 1790 by John White, who arrived on the First Fleet as the principal surgeon, later to become Surgeon General of NSW. (He absolutely loathed Australia which he found "so hateful as only to merit execration and curses”). Despite this he collected and described many native animals and plants. Early specimens of the Green Tree Frog sent back to England in collections had been preserved in alcohol (we even know the names of the distillers) which dissolved out the unstable yellow component of the skin pigmentation, leaving the insoluble bright blue base colour, and that is how the name was given. Although the name is clearly a false description of the frog, under international conventions it cannot be changed. At one time the common name of this frog was White’s Tree Frog.

White also made another mistake in describing the specimen as having four fingers when they clearly have five. White seemed to have difficulty with numbers greater than three. He also described, and named the Potoroo as having three toes – they actually have four. However he was a caring and competent medico.

Dietary habits

Watching the frogs eat is interesting. They use the sticky underside of their stubby tongues to grasp the prey, then flip it into their mouths and use their big hands to shovel in any oversized parts. Cockroaches in particular make a crunching sound when the frog’s jaws clamp down. The frogs are so unafraid that even wild ones can be hand fed by holding live food or wriggling dead insects in front of their noses. L. caerulea are our second largest frog (up to 120 mm) and in nature their diet is incredible, it includes insects, other frogs, mice, birds, bats and even small snakes – in fact, anything they can cram into their large mouths.

Frogs removed some distance from inconvenient places like toilets, laundry drains, ventilators etc quickly find their way back to that favoured position. This homing ability is not clearly understood but it is likely that the senses of smell and hearing are involved. Jack(boot) would make a good case study.

The repetitive barking call of this species, usually heard on rainy nights is probably the here I am call, but the frogs can also give an agonising scream when stressed or annoyed. Although they often huddle together, we have observed one shrieking when another tried to climb over it. We have also experienced one in our yard making a loud, pitiful cry lasting several minutes. Then, for no reason we could discern, it simply appeared to shut down. Within half-an-hour it was dead.

The Australian Green Tree Frog secretes compounds from its skin which have been studied for antibacterial and antiviral properties and synthesised versions form the basis of several drugs used in modern medicine. One unique secretion, called caerulein, has also been synthetically manufactured and is used in treatment of hypertension and detection of gall bladder stones.

The conservation status at this time of Litoria caerulea is Least Concern but unless we stop polluting and devastating our environment this charming frog will not survive.

Important: frogs should only be handled with clean, damp hands, free from detergents and cosmetic applications.

Article by Kon Hepers