How Cobras Spit With Perfect Accuracy

Spitting cobra takes aim at a human face. CREDIT: Frank Luerweg/University of Bonn.

Spitting cobras don't truly spit venom. But they are incredibly accurate shooters, hitting a target — the victim's eyes — from 2 feet (60 cm) away with impressive accuracy, studies have shown.

New research confirms how they do it.

Scientists have long known that spitting cobras don't actually spit. Rather, muscle contractions squeeze the cobra's venom gland, forcing venom to stream out of the snake's fangs, explains Bruce Young, a researcher at the University of Massachusetts. The muscles can produce enough pressure to spray venom up to 6 feet (nearly 2 meters).

To be effective, venom — a cocktail of neurotoxins and tissue-attacking poisons — must make contact with an attacker's eyes, where it causes severe pain and possibly blindness.

Turns out the venom does not hit a victim in just one spot. Instead, the venom lands in complex geometric patterns.

A European study in 2005 showed that cobras do aim for the eyes, but their venom is shot out in a spray rather than a stream.

Young and his team now have figured out how this spray is generated. They used high-speed photography and electromyography (EMG) to detect contractions of cobra head and neck muscles. The snakes engage their head and neck muscles a split second before "spitting" to rotate their heads, then jerk them from side to side.

"The venom-delivery system functions to propel the venom forward while the [head and neck] muscles produce rapid oscillations of the head that … disperse the venom, presumably maximizing the chance that a portion of the spat venom will contact the eye," the researchers write in the journal Physiological and Biochemical Zoology.

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