Wednesday, October 13, 2010

Temperature and the Placticity of Neonate Snakes


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.

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