Spitting cobra takes aim at a human face.
Credit: Frank Luerweg/University of Bonn.
A spitting cobra can launch its venom well across the average dinner table. If this projectile of neurotoxins and tissue-attacking poisons should land in the recipient's eye, it will cause a severe, stinging pain, and possibly blindness.
This appears to be the intent of the spitting behavior - to knock out the eyes. Researchers at the University of Bonn have put some cobras through target practice and found that the spitters rarely miss.
"In the literature it often says: they aim at the eyes," said Guido Westhoff. "However, up to now nobody has investigated it."
Whites of their eyes
Katja Tzschätzsch, Westhoff's student, performed experiments on four red Mozambique cobras and six black-necked spitting cobras. Standing behind a plastic visor, she was able to record where the snakes were aiming when they spat at her.
"The snakes really do spit only at moving faces," Tzschätzsch said. "Movements involving the hand elicited no response from any of the snakes."
Tzschätzsch also used photographs of people. Most of her cobras did not fall for the fake faces, but two of them did, and one of these even went after a photo that had its eyes removed digitally.
The accuracy of the snakes, both with live faces and photos, was impressive. The black-necked cobras hit the eyes eight out of ten tries, while the red Mozambique cobras scored a perfect 100 percent.
To achieve such dead-on spitting, the researchers discovered in high-speed video that the snakes cheat a bit. They shake their head rapidly while spraying the toxin - increasing the area that gets struck.
It's a bit like using a garden hose to water the flowers of an entire flowerbed, Westhoff explained.
Spit or bite
Although the cobras are fine shots, they have a better way to deliver their venom: biting.
"Cobras only spit when they feel threatened, not to kill their prey," Westhoff said. "Anything else is a myth."
When a cobra bites a chosen victim, the poison is injected into the bloodstream, where it interferes fatally with the respiratory system. That means you can die. Human beings are not on the cobras' menu, however, so the spitting is used merely as a means of self-defense. It is an instinct in even the youngest snakes.
"I was once attacked by a spitting cobra which had just emerged from its shell," Westhoff said. "It practically spat at me out of its shell."