Why are snakes so cold

zoology : When snakes fall out of trees

Scientists studying the agility of arboreal snakes have started with precise descriptions of when and how reptiles fall from their trees.

Like all cold-blooded animals, snakes cannot control their body temperature. Instead, they adapt to the ambient conditions and, for example, slow down their movements when temperatures drop. When it gets particularly cold, some reptiles become completely immobile, which can cause problems. For example, a cold snap in Florida last winter caused iguanas to fall out of their tree houses.

For their research, Gary Gerald and his colleagues at Miami University in Ohio recorded the speed, posture and balance skills of corn snakes (Elaphe guttata) on horizontal bars at 10 ° C, 20 ° C and 30 ° C. The snakes were exposed to temperatures in a climate-controlled laboratory for two hours before being encouraged to cross the "branches", which were 3, 6 and 10 centimeters in diameter. Observers stood underneath to catch the snakes in case they fell, and safety cushions were placed under the artificial trees in case the observers missed or dropped the falling snakes.

Snakes in a precarious position

The team reports in the Journal of Experimental Zoology (1) that the snakes moved faster at high temperatures and were more likely to stretch out on branches of all diameters. At lower temperatures, the snakes moved much more slowly and assumed a coiled posture - their bodies twisted around the branches for stability.

The snakes were ten times more likely to fall in the coldest temperatures than the warmest, even if they were still agile. Falling and twisting postures suggest that temperatures have an impact on balance as well as mobility, the researchers say.

The snakes, which were exposed to colder temperatures, weren't particularly cooperative in this experiment. Possibly knowing what was in store for them, they often did not even try to cross the branches. In such cases of insubordination, the scientists had to tickle the underside of the snake's tail in order to nudge it.

Contrary to all assumptions, the snakes fell less from thin branches than from thick ones in cold temperatures, perhaps because they could wind around the thin branches better.

Their agility in thin branches gives snakes a certain advantage over other arboreal animals, says Gerald. "People often think snakes are at a disadvantage because they don't have legs, but in the trees it undoubtedly helps them move forward."

The study could help explain some aspects of snake ecology. "The fact that so many snakes crash when it gets cold could explain why so few arboreal snake species can be found outside of the tropics," says biologist and snake expert John Socha of the University of Chicago in Illinois.

(1) Gerald, G.W., Mackey, M.J. & Claussen, D.L.J. Exp. Zool. 309A, 147-156 (2008).

This article was first published on March 4th, 2008 at [email protected] doi: 10.1038 / news.2008.641. Translation: Sonja Hinte. © 2007, Macmillan Publishers Ltd

Now new: We give you 4 weeks of Tagesspiegel Plus! To home page