Spitting cobras are snakes that pose a double threat. Like other venomous snakes their bites can seriously injure or kill, but they have a second weapon up their sleeves (or should I say scales) – they can launch venom from their fangs right into the eyes of attackers.
This venom causes searing eye pain, horrendous eye damage, and sometimes permanent blindness. And, surprisingly, humans might be to blame.
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How many species of spitting cobras are there?
There are fifteen species of spitting cobra.
Fourteen of these species are true cobras, and belong in the genus Naja. These fourteen species are split into two groups: African spitting cobras and Asian spitting cobras, and these two groups independently evolved the ability to spit venom.
One species, the rinkhals, is not a true cobra but has also evolved the ability to spit venom.
Where do spitting cobras live?
African spitting cobras and rinkhals are native to Africa. Asian spitting cobras are mostly found in south and southeast Asia.
Spitting cobras occupy a range of habitats. African spitting cobras tend to prefer dry habitats, while some Asian species thrive in rainforests.
Why do they spit?
Spitting cobras don’t spit to kill. To kill, they bite and inject their prey – usually small mammals, amphibians and reptiles – with venom.
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When they spit, they are simply trying to deter a threat.
This is clear not just from the behaviour of the snakes, who spit at threats rather than at food, but also the chemical make-up of their venom.
While snakes who use venom only to hunt tend to have neurotoxic venom – that is, venom that shuts down the central nervous system and therefore kills – spitting cobras have venom specifically formulated to inflict pain. Particularly, it seems, on mammals.
Their venom causes searing, unbearable burning pain when it gets into our eyes, and if not quickly washed out, it can lead to blindness. While it does not kill the target animal, it certainly deters them from getting any closer!
How do spitting cobras spit?
Technically, they don’t really spit. Their venom is pushed out of holes in their fangs, and can travel as far as 10 feet.
It manages to go such a distance because it is released at very high pressure – like a jet spray. This pressure is created by the contraction of muscles around the venom glands, which squeeze venom into the fangs and out of a small hole in each.
Have spitting cobras got good aim?
Spitting cobras have incredibly good aim. They always aim for the eyes – where they inflict the most damage – and they are successful over 90% of the time.
This takes some crazy calculations. To successfully hit a target’s eyes, the snake needs to factor in the direction of the target’s movement, the speed of their own movement, and the time delay between the venom leaving their fangs and reaching the target – who can be up to 3 metres away.
To help make sure the venom reaches its target, the snake also rotates its head from side to side as it spits. This covers a wider area with venom and results in a higher likelihood of hitting a (bulls)eye.
Just think how hard it must be to hit a target as small as an eye from three metres away, while both you and the target are moving – and these snakes manage to do it nine out of ten times!
Why did spitting first evolve?
Spitting clearly evolved to defend against threats, but scientists think that cobras might have evolved to spit in response to one threat in particular: the threat posed by humans.
When scientists looked at spitting cobra evolutionary history, they saw something remarkable: the ability to spit seemed to evolve at around the same time that early hominins emerged in Africa, and again when hominins migrated to Asia. This suggests there might be a link.
Early humans likely posed a threat to cobras, because we probably killed them both defensively and for food. Therefore, cobras may have evolved to spit in order to deter our ancestors from harming them.
Essentially, cobras might have begun spitting because of us!
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