Snake fools attackers by changing its eyes to look like a viper

10 October 2016

By Vera Novais
 

You pick up a harmless snake and it turns into a deadly viper.

This is what happened to Colin Strine from Sakaerat Environmental Research Station in Nakhon Ratchasima, Thailand, during a field trip with his team to a biodiversity hotspot in the north-east of the country where at least 176 snake species are found. He instinctively dropped it and the snake fled.

But it turns out Strine might have been fooled by a never-before-seen behaviour: a snake changing the shape of its eye pupils when attacked to resemble those of a deadly relation.

Further investigation revealed that the snake he picked up really was harmless: a mock viper (Psammodynastes pulverulentus) that has evolved several features to look like its venomous distant cousins, Malayan pit vipers (Calloselasma rhodostoma).

“Thailand is the land of mimics for snakes,” says Strine. “Most of the highly venomous snakes also have a non-venomous mimic counterpart.”

Eye spy

This is true of the mock viper, which has the triangular head, cryptic colour pattern and enlarged front teeth of its lethal relation. But it also appears to have gone a step further and evolved to change the shape of its rounded pupils into the vertical slits typical of a venomous viper when attacked.

Continued