The European viper (genus Vipera) is designed to deceive, it seems.
New research from Finland suggests that the characteristic zig-zag pattern on its back can perform three different functions as needed when predators are around.
At first it helps the snake remain undetected, but upon exposure it can both provide a conspicuous warning of its potential to defend itself and produce an illusionary effect that hides its movement if it chooses to flee.
It’s common for prey species to use different colour patterns to achieve these three different aims – obscure, warn and evade – but not to do all three with one pattern.
The research was carried out by Janne Valkonen and Johanna Mappes from the University of Jyväskylä and is described in the journal Animal Behaviour.
The most significant finding, they say, deals with a particular class of illusion generated by the zig-zag pattern. Just as a rapid series of still pictures can produce a smooth animation, the rapid flickering from the zigs and zags of a fleeing snake can produce a solid shape.
The researchers measured the speed of fleeing snakes and calculated the flicker rate of the zig-zag. They found that the zig-zag moved quickly enough to produce a “flicker-fusion effect” to mammalian predators, although the quicker eyes of a raptor won’t be fooled.
“Our results show that the zigzag pattern reduced detectability regardless of base colouration or posture of the snake,” they write in their paper.
More broadly, the findings imply a far broader scope for the evolution of colour patterns and antipredator adaptations than “simple one-pattern-to-one function relations”, they suggest.
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