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Australian Tiger Snakes, Notechis scutatus. JCM |
In thinking about the
impact of the global warming and the evapotranspiration rate on reptiles I did
some Internet searching and found an article published earlier this year that
experimentally examined how snakes would respond to temperature shifts after they
were raised under different thermal conditions as neonates. Aubret and Shine
(2010) used captive born Australian Tiger Snakes, Notechis scutatus, (Family
Elapidae) to see how snakes respond to temperature changes. Forty-three Tiger
Snakes were raised in cold (19-22C), intermediate (19-26C) and hot (19-37C)
thermal gradients. The snakes adjusted their thermal behavior so that when they
were tested 14 months later their body temperature, speed of movement, and
anti-predator behavior did not differ between the groups - the snakes had
modified their behaviors to compensate for the different temperature regimes
under which they were raised in. However, when the temperatures the snakes were
kept at were changed to follow year to year variations, the snakes failed to
adjust their behaviors. Snakes raised at cool temperatures and then shifted to
hot temperatures showed a higher mean body temperature for at least two months
after they were exposed to the new thermal conditions. This suggests that the
temperatures snakes experienced when young impact their thermal behavior later
in life. So, the young snakes proved to be quite flexible in their ability to
adapt to the temperature regimes they were exposed to. But, as they aged, they
continued to use the same thermal regulatory behaviors when placed into new
thermal environments, even though those behaviors were inappropriate for their
current thermal environment. Aubret and Shine suggest the mean body temperature
depends more on the individual snake's early experience than on the thermal
opportunities present at a given point in time. And, that the challenge of
adapting to global warming is not the shift in the mean values but the
increases in annual variations in temperatures. As the previous post suggests
large areas of the Southern Hemisphere are drying and changes in the vegetation
and fauna can be expected. Ultimately this trend will result in extinctions and
produce a greatly reduced biodiversity.
Aubret, F. and R.
Shine. 2010. Thermal plasticity in young snakes: how will climate change affect
the thermoregulatory tactics of ectotherms? The Journal of Experimental Biology 213:242-248.