The new tadpoles are happily chewing through the algae in my pond and the water is slowly turning crystal clear. After a couple of days their pale colour darkened and they blend in well with the murky water.
Two frogs from last year’s tadpoles live in and around the pond. There might be more, but in recent months I’ve only seen two at a time. When I take photos I can usually differenciate between them due to their skin patterns.
Frog 1 on 20 November
Same frog on 10 December (the dark green on its leg in dried algae from swimming in the pond)
Frog 2 on 10 December. The solid green above the mouth is the main pattern difference I notice
They each had a favourite spot on the Westringia bush next to the pond where I always found them during the day. Until Frog 1 stole Frog 2’s spot.
I found Frog 2 on the other side of the Westringia bush, before froggy hopped away because I got too close.
These last photos show the frogs with a slightly different shade of green, but patterns match the earlier photos. Motorbike frogs (Litoria moorei) can change their skin colour, like the tadpoles did. Skin cells called chromatophores allow this.
“Hormones produce the colour change by changing the shape of the chromatophores, moving the pigment around inside them & altering the intensity of light they reflect.” – Beasts & Blossoms
This instagram post has more on the biology of colour change in motorbike frogs:
It’s that time again – #frogfriday! ☺ This is another motorbike frog (Litoria moorei), but this one is exhibiting much lighter colouration than the one I posted last week. I found that one at night, while this one was sitting out in full sun at 11am – his pale colouration not only blends in with the branch he’s sitting on (for camouflage from predators), but also helps prevent overheating & drying out in the full sun. Frogs of many nocturnal species bask in sunlight for at least short periods of time here & there (& some for extended periods of time daily), as they need exposure to UVB radiation to synthesize vitamin D3, which is necessary for the absorption of calcium & skeletal development, amongst other things. This is a really simplified explanation & could easily be a full post on its own, but I have something else in mind for this one…. chromatophores! Chromatophores are the cells in frog skin that are responsible for their colour & (in many species) their ability to change colour. There are three types of chromatophores that combine to create colour: (1) the bottom layer is made up of melanophores, which contain the brown – black pigment melanin (this is the same pigment found in our skin); (2) the middle layer consists of iridophores, which reflect light or are iridescent; and (3) the upper layer is made up of xanthophores, which contain yellow pigments. In most green frogs, the iridophores reflect blue light, & this then travels through the yellow xanthophores (& blue + yellow = green). In species like motorbike frogs that can change their colouration to match their background, at least within the light / dark green to light / dark brown range, hormones produce the colour change by changing the shape of the chromatophores, moving the pigment around inside them & altering the intensity of light they reflect. Every once in a while, a frog that should be green will be blue instead – this is because it’s axanthic, or missing the layer of yellow xanthophores in its skin. Years ago in north Queensland, I saw a axanthic green tree frog (Litoria caerulea) – instead of turning brown to match a dark background, he turned purple!
- Frog Watch has information about frogs in WA. There are recordings of breeding calls so you can ID frogs you hear in winter in wetlands or your garden.
- WA Gould League Tadpole Exchange Program.
- Aplin, Piano & Sleep (2002) Building Frog Friendly Gardens. WA Museum: Perth.