Spitting Cobras are a major danger in Africa and Southeast Asia. They have an unnerving ability to spit venom in the eyes of even the fastest moving targets. Why do they have such good aim?
Bruce Young, of University of Massachusetts Lowell, researched this in the most traditional of scientific ways - by having spitting cobras attack him hundreds of times.
He began his experiments in South Africa, where he protected himself with hard, transparent plastic, and observed the trails of venom that hit. Later, at Horst Bleckmann's lab in the University of Bonn, Young was fitted with goggles and an accelerometer, in order to better track how his head was moving, and how the cobras were responding to it.
Young was uniquely successful at getting the snakes to attack, and over six weeks, the team recorded more than 100 spits. Young would taunt them by weaving his head back and forth, and then a sudden jerk of his head would cause the snake to attack. By combining the data from the accelerometer with high speed footage of the attack, the researchers were able to divide the action into two discrete stages: First the snakes begin by tracking their victim; second, they predict their victim's next move.
While Young moved slowly, the snake would track his movement. As soon as he moved quickly — something easily construed as an act of aggression — the snake would spit, taking just 200 milliseconds to shoot out the venom. However, 200 milliseconds is long enough for a fast-moving creature to shift enough that it won't be hit. And that's where the snake's predictive powers come into play. It moves its head in the direction the target's eyes are moving and aims there. This method almost always results in a direct hit.
By combining the two methods, the cobra gains unerring accuracy and speed, and is able to disable animals far larger than it.
Paper published in the Journal of Experimental Biology