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No, shape of snake’s head doesn’t show whether it’s venomous or not

A graphic doing the rounds on Facebook in South Africa claims to show how you can tell the difference between venomous and non-venomous snakes – by the shape of their heads.

Snake venom is highly toxic saliva, or spit, that venomous snakes use to catch prey and defend themselves from other predators.

South Africa has both venomous snakes such as the puff adder, and non-venomous snakes such as the brown house snake.

The brown house snake is a constrictor because it uses its muscle power instead of venom to kill prey. Another well-known snake of this type is the boa constrictor

The graphic has an illustration of two snake heads, one with a triangle on top of it, the other with an oval shape. The triangle-headed snake is labelled as “venomous”, and the snake with the oval head as “non-venomous”.

The graphic is copyrighted “3 MINUTE HACKS”. But would this “hack” keep you safe if you came across a snake? No.


Harmless triangle-heads and deadly oval-heads

In a list of nine of the world’s deadliest snakes, Britannica identifies the boomslang and the black mamba as two snakes with deadly amounts of venom. Both are found in South Africa.

And both have an oval-shaped head, even though they are highly venomous.

The coral snake, part of the cobra family and found mainly in the tropics, is another example of a highly venomous oval-headed snake.

On the other hand, harmless snakes can have triangle-shaped heads.

National Geographic explains that because there are many dangerously venomous snakes with triangular heads, some harmless species of snake mimic the shape to avoid attack. Snakes like the grass snake and viperine snake flatten their normally narrow head into a triangle when they feel threatened.

‘It’s a popular myth’

The African Snakebite Institute has already debunked similar claims on how to tell if a snake is venomous or not, so Africa Check asked them about the graphic.

The institute’s Johan Marais told us that its claim “is a popular myth”. 

He said it was similar to another myth, that the shape of a snake’s eyes can tell whether it’s venomous or not: “round eyes = harmless snakes and vertical eyes = venomous snakes”. 

“Again not true,” he said. “There is no easy way of distinguishing between harmless and highly venomous snakes."

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