colour change is also very short in comparison,
being as little as four days from start to finish!
mean
mode
range
beginning - weeks
38
37
35-45
duration - days
8
4
3-31
This table refers to data collected from 2007, 2008 and 2009
clutches. The modal values are more indicative as some individuals
were slow to start feeding, resulting in a skewed mean value.
So, what could the temporal trigger be? There is a
fundamental difference between climatic regimes on
Cape York Peninsula and the equatorial rainforests
within the species’ distribution. Cape York is
heavily influenced by seasonality (wet and dry, with
fluctuations in temperature and photoperiod), whereas
equatorial habitats in the north have a more uniform
climate throughout the year. Seasonal variation might
be instrumental in the timing and short duration of
native GTPs’ colour change.
I am well aware of the dangers of extrapolating from
data derived from captive snakes, but if we accept that
the colour change takes place in June/July (as it does
in captivity), which is the onset of the dry season, then
we can predict that this also coincides with a shortage
of small frogs because they metamorphose during the
monsoonal rains (January–March). It would therefore
be perfect timing for the now-green juvenile GTPs to
switch habitat and prey items.
Ontogenetic colour change is a physiological process
controlled by either internal signals (e.g. hormonal
activity) or by some environmental cues. It’s a highly