Monday, December 8, 2008

Sidewinding unique to caenophidian snakes

Sidewinding is a type of locomotion unique to caenophidian snakes, used to move across loose or slippery substrates. It is most often used by the Saharan horned viper, Cerastes cerastes, and the sidewinder rattlesnake, Crotalus cerastes, to move across loose desert sands, but it is also used by Homalopsine snakes in Southeast Asia to move across tidal mud flats. Any number of caenophidian snakes can be induced to sidewind on artificial smooth surfaces, though difficulty in getting them to do so and their proficiency at it vary greatly.In the resultant movement, the snake's body is always in static (as opposed to sliding) contact when touching the ground. The head seems to be "thrown" forward, and the body follows, being lifted from the prior position and moved forward to lay on the ground ahead of where it was originally. Meanwhile, the head is being thrown forward again. In this way, the snake slowly progresses at an angle, leaving a series of mostly straight, J-shaped tracks. Because the snake's body is in static contact with the ground, imprints of the belly scales can be seen in the tracks, and each track is almost exactly as long as the snake.Crude animated line-drawing shows the locomotor pattern of sidewinding. The light brown areas are the tracks left behind, and also indicate where the body of the snake touched the ground.

No comments: