Spider builds life-sized decoys

By | July 7, 2009

C. mulmeinensis with decoys of itselfimage: An adult C. mulmeinensis alongside decoy prey pellets (L) and decoy egg sacs (R)

There is a species of spider that builds models of itself, which it uses as decoys to distract predators. The spider may be the first example of an animal building a life-size replica of its own body.

So believe the scientists who made the discovery, which is published in the journal Animal Behaviour.  The arachnid’s behaviour also offers one explanation for why many spiders like to decorate their webs with strange-looking ornaments.

Many animals try to divert the attentions of predators by becoming masters of disguise. Some try to avoid being seen altogether by using camouflage to blend in against a background, such as the peppered moth evolving motley wings that blend into tree bark, or stick insects that look like sticks.

Others evolve more conspicuous ornaments designed to distract a predator, such as butterflies that grow large eyespots or lizards that quickly move colourful tails, which they detach from their bodies if grabbed. This latter strategy has puzzled biologists, because attracting predators in the first place is usually a bad idea.

One hypothesis is that animals which grow conspicuous ornaments benefit overall, because directing a predator to attack an expendable part of the body, such as the lizard’s tail, outweighs the costs of attracting the attention of the predator in the first place. …

But animals do not tend to actually build life-like replica models of themselves to act as decoys. However, that is exactly what a species of orb spider called Cyclosa mulmeinensis does, biologists Ling Tseng and I-Min Tso of Tunghai University in Taichung, Taiwan, have discovered.

via BBC – Earth News – Spider builds life-sized decoys.

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