Meet the snake that pretends to be an insect to catch prey

New Delhi | October 11, 2025 11:38 AM IST

3 min read

A rare Iranian viper hunts with a convincing fake: a spider-shaped tail it wiggles to lure birds (Source: Wikimedia Commons)

In the rocky hills of western Iran, one of the world’s strangest snakes lives. At first glance, the spider-tailed horned viper (Pseudocerastes urarachnoides) looks like any other desert viper—camouflaged against pale stone, motionless, waiting. But then its tail twitches, and the illusion begins.

Instead of a simple tip, this snake’s tail ends in a bulb with spiny, leg-like scales that move just like a spider scuttling about. Hungry birds, thinking they’ve spotted an easy snack, swoop down to grab the “insect.” That’s when the viper strikes—lightning fast, in less than a quarter of a second. The hunter becomes the hunted.

Although locals had long spoken about a snake with a “spider tail,” scientists only formally described the species in 2006 after studying museum specimens and eventually finding living snakes in Iran’s Zagros Mountains. What stood out was the tail: a decoy so elaborate that no other reptile in the world has anything quite like it.

How the trick works

When the viper lies coiled among pale rocks, its body blends in almost perfectly with the landscape. All that moves is the tip of its tail, which the snake waves in jerky little bursts, just like a spider. To a bird on the lookout for insects, it’s irresistible. As soon as the bird lands, the viper lunges, sinking its venomous fangs into the prey.

Field studies have shown that adult vipers mostly use this strategy to catch small migratory birds, while younger snakes, whose tails haven’t yet developed the full spider-like lure, feed more often on lizards. In other words, the “fake spider” grows more convincing as the snake itself matures.

When the viper lies coiled among pale rocks, its body blends in almost perfectly with the landscape (Source: Wikimedia Commons)

Evolution’s little masterpiece

Many snakes use their tails to wiggle and tease prey, but this viper takes it to an extreme. Over thousands of years, natural selection has shaped a tail that doesn’t just move like a spider, but actually looks like one, right down to the “body” and “legs.” For a predator that relies on ambush in a harsh environment, this mimicry is a clever way of turning the tables on fast-moving birds.

Because the spider-tailed viper lives only in a small region of Iran, conservationists worry about its survival. It was added to CITES Appendix II in 2019, which means trade in the species is restricted, and in 2022, the IUCN Red List updated its status to Near Threatened. For such a rare and unusual creature, these protections are an important step.

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