Left and below:
albino Darwin
Carpet Python
with her clutch.
Images by
R.M.T.
between pythons in the northern hemisphere have
also indicated that species that frequently demon-
strate shivering thermogenesis have ranges that
extend to higher latitudes than their non-shivering
counterparts.
generated by maternal endogenous heat production
may also have benefits for the mother python. For,
although shivering thermogenesis certainly entails a
metabolic cost, it also means that by minimizing the
duration of the incubation period (during which most
females fast), the female will have more time to feed
and increase her body mass before the onset of
winter and the next breeding season. Similarly,
earlier hatching may also benefit the offspring in
allowing them to have a longer feeding period prior
to winter, as well as assisting them to more rapidly
attain a body size that makes them less vulnerable
to predation, and even ultimately attaining sexual
maturity at an earlier age.
Shivering thermogenesis also enables snakes to
extend their distribution into cooler latitudes. For
example, it appears that this behaviour allows
M. s. spilota, which has by far the most southerly
distribution of all Australian pythons, extending as
far south as 37.5 o S in Victoria, to occupy areas
where ambient temperatures would otherwise
preclude successful hatching. Comparisons
Shivering thermogenesis has been recorded in all
genera of Australian pythons, but it is unknown
whether all members of Pythonidae are capable of
this physiological feat. There are contradictory
reports for different species, but failure to observe
this behaviour does not mean that a species is
incapable of or doesn’t perform shivering ther-
mogenesis. For some species like Reticulated
Pythons (Python reticulatus) and African Rock
Pythons (Python sebae), the ramped up metabolism
necessary to generate heat is really only detectable
by measuring oxygen consumption and heat
production, but for Burmese Pythons (Python
bivittatus), their thermogenic activity is evident as
they rhythmically shiver and twitch their muscles.
Failure to observe shivering thermogenesis can also
be attributed to the sensitivity of brooding pythons to
being observed and disturbed, as well as the
facultative nature of this behaviour, also known as
‘facultative endothermy’. Due to the high energy
expenditure involved in endogenous heat produc-
tion, it is unsurprising that brooding pythons only
engage in this physiological activity when environ-
mental temperatures fall to levels which may
jeopardise the development of their offspring.
Female Water Pythons (Liasis fuscus) will brood
their eggs and transfer heat by shivering ther-
mogenesis when their nests are located in tree root
boles where ambient temperatures can be variable
and quite low, but if their eggs are laid in the
abandoned burrows of varanids, these provide a
favourable, warm, stable environment for egg
development, and the females need not brood or
heat their e