The hourglass mark on its dorsum is attractive, and that is why I call it the time keeper. We found this frog while we were cleaning and pruning the area around our fish pond. Sarah was throwing away some rotten twigs and leaves when she felt something cold and creepy leap on to her ๐Ÿ˜ฎ

polypedates occidentalis

The photos above and below are of the same frog, taken a few minutes apart. Itย changed its color from an off-whiteย to a brownish tone! This happened when the frog had moved from its previous location into a bunch of dried leaves and twigs. Such an ability of animals to change its color is called metachrosis.

Metachrosis could be due to several reasons: like theย light/temperature/moisture play aย vital role in changingย the colour. Some amphibians exposed to cold temperature and darkness often exhibit a darkening of their skin due to a melanophorotropic hormone (dark brown – black pigments) release. At higher temperature and light their color tend to get pale due to melanophore contraction. This color change is probably done as part of a hydro-thermal regulation (for regulating its moisture and temperature).

polypedates occidentalis

We are not sure if this frog exhibited metchrosis for such a regulation. At first sight we felt it was an instance of “crypsis“, where the animal has the ability to avoid getting noticed, through camouflage, mimicry, etc. However, studies shows that crypsis alone may not be the case of frogs like this one, and hydro-thermal regulations also play a major role. So probably a short time between the dried leaves with less light and colder environment let it change the shade from pale to dark.

The frog in the picture is polypedates occidentalis. To my amazement, the species was identified and named only recently, in 2006 ๐Ÿ˜ฏ (link provided below). Hence data is deficient to tell if p.occidentalis is a rare species or not. Probably it is a common species for the western ghats region.

A similar frog is the Common Indian Tree Frog, polypedates maculatus, which also has an hourglass like mark on its dorsum. This one is present in central India and neighboring countries.


Date:ย 26ย Oct 2008
Location: @ home, Kottayam, Kerala, India
Camera: Nikon D80 + Tamron SP AF90mm f/2.8 Di Macro Lens


References:
1. Feder M. E., Burggren W. W., 1992: Environmental physiology of the amphibians, University of Chicago Press.
2. Das I., and Dutta S. K., 2006: New Species of Polypedates (Anura: Rhacophoridae) from the Western Ghats, Southwest India, Journal of Herpetology, 40, 2, 214-220 [
link].
3. Dr. K. V. Gururaja, Indian Institute of Science, Bangalore.

ย 


P.S. It has been a while since I posted the last article. Time has been flying since pratyahara, and work also is getting tight these days. Anyways timekeeper is here to save me for a while ๐Ÿ™‚ Buon Anno!

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