Sunday, February 01, 2009
Snakes that play the corpse for their foes
Snakes in trees often simply relax and fall to the ground out of harm's way if they are threatened, but there are snakes, such as the European grass snake and the American hognose, that are truly consummate actors. Despite the fact that a snake, dead or alive, cannot fall over a 'dying' grass or hognose snake will lie belly-up if it is threatened.
The sagging jaw, lolling tongue and deathly expression are all quite convincing, but the effect is sometimes spoiled by the wriggling involved in staying upside-down. The snake's instinctive desire to remain belly-up is so strong that it betrays itself by writhing back into its upside-down death pose if a predator tries, out of curiousity, to roll it over.
The prize for the most impressive use of props for playing dead goes to the West Indian wood snake. When threatened, this small boa twists itself into a taut coil, mimicking the stiffness of death. Fluids coating the snake's scales give off a foul stench of decomposing flesh to add to the success of the illusion.
As a final effect, blood, released from special tiny blood vessels, flushes the eyes of the coiled 'corpse' a dull red, and trickles from its gaping mouth. Thus a predator, such as a mongoose, is led to believe that the snake is dead - and that it has been so for some time.
Unless the predator is particularly hungry, or has a taste for rotting flesh, this performance is usually enough to put it off, or to make it hesitate for long enough to give the snake a chance to make its escape.