STRUCTURAL COLOUR: STAR SPECIES NUMBER 2
Name: Australian green tree frog
Special Power: Changes Colour When Dead!
A zombie frog?
If you look at early paintings of the green tree frog you will see that it is coloured blue. This is because the artists were painting their impressions of living frogs from deceased, preserved specimens (in death the green tree frog is blue in colour – but this is structural colour, not pigment). In life it has active pigment cells that turn the frog green.
The Australian green tree frog is a member of the tree frog family Hylidae which is endemic to Australia and New Guinea and includes about 160 species. Larger than most Australian frogs, it reaches 10 cm (4 inches) or more in length. Its average lifespan in captivity, about 16 years, is long compared with most frogs. Docile and well suited to living near human dwellings, Australian green tree frogs are often found on window sills or inside houses, eating insects drawn by the light. The green tree frog screams when it is in danger to scare off its foe, and squeaks when it is touched.
The green tree frog was the first Australian frog to be scientifically described; the original specimen found its way into the collection of Sir Joseph Banks, but was destroyed when the Hunterian Museum at the Royal College of Surgeons in London was bombed in World War II. The common name of the species, “White’s tree frog”, is in honor of John White’s first description in 1790.
The species was originally called the “blue frog” (Rana caerulea) despite its green colour. According to Wikipedia “The specimens White sent to England were damaged by the preservative and appeared blue” – hence the colour of the frog in the illustration above. This is incorrect because the colour of the frog is actually caused by active, living, yellow pigments covered in a blue layer of structural colouration; when dead the yellow pigments cease to function and the frog is left with a blue appearance (blue and yellow, of course, make green – a surprisingly difficult colour to manufacture in living nature).