Formanowicz, D.R. Jr. 1990. The antipredatory efficiency of spider leg autonomy. Animal Behavior 40: 400-401.
Body part autonomy has been cited as a defense against an attacking predator. Spiders have been noted to autotomize their legs when attacked. How effective is leg autonomy for increasing survival during a predatory attack?
The effectiveness of autonomy in increasing survival from a predatory attack has examined in lizards, salamanders, molluscs, and crab, which all autotomize limbs. Although we know spiders autotomizes their legs, there is no evident that shows that this action increases the chance of survival during predatory attacks.
A spider was introduced into a home chamber of a randomly chosen predator (centipede or scorpion) and observed until a capture attempt took place. "The fate of each spider was scored as killed and eaten, survived using leg autonomy or survived with no leg autonomy." None of the spiders introduced to a centipede survived and no leg autonomy occurred because spiders were immediately grabbed by the centipede with its poison claws and bitten several times. 42% of spiders that were introduced to a scorpion survived and 82% of those used leg autonomy to escape. No spider that autotomized was killed.
Leg autonomy by spiders can be an effective defense against predators. The effectiveness of leg autonomy as a predatory defense is dependent on the type of predator. Leg autonomy was not an effective defense against a centipede predator. The difference in effectiveness of leg autonomy in these spiders was the result of differences in the prey capture behaviour and morphology of the two different predatory animals.
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