Thursday, October 23, 2008

Spider Eats Bird? You think it is nonsense?

Photos of a mammoth spider devouring a bird in a Queensland backyard are sweeping email inboxes - and according to experts, they are real.

Several photos of a giant spider eating an unfortunate bird have been posted on Thursday’s (October 23) edition of Australia’s Cairns Post. The photos - which are reported to have been taken this week in Atherton, west of Cairns - show the spider clenching its legs around a lifeless bird trapped in a web. The images first appeared on website forum Ars Technica on October 16.

Head spider keeper at the Australian Reptile Park at Gosford on NSW central coast, Joel Shakespeare, said the spider was from the species Nephila edulis, better known as the edible golden silk orb-weaver. "Normally they prey on large insects… it’s unusual to see one eating a bird," he told. Mr Shakepeare said he had seen Golden Orb Weaver spiders as big as a human hand but the northern species in tropical areas were known to grow larger. The average body of the female of the species is generally four times (23 mm - less than an inch) the size of the male (6 mm - less than a quarter of an inch), with a leg-span that can extend to that of a man’s hand. The spider eating the bird in the photo is a female. Some golden orb weavers have been found to reach 45 mm (less than two inches).

Queensland Museum identified the bird as a native finch called the Chestnut-breasted Mannikin. The bird, which appears frozen in an angel-like pose, most likely flew into the web and got caught, according to Mr Shakepeare. "It wouldn’t eat the whole bird," he said. But the spider would probably prepare a liquid soup with the finch - as it does with insects - and discard of what it doesn’t need. "It uses its venom to break down the bird for eating and what it leaves is a food parcel," he said.

Greg Czechura from Queensland Museum said cases of the Golden Orb Weaver eating small birds were "well known but rare". "It builds a very strong web," he said. But he said the spider would not have attacked until the bird weakened. "They blunder into [the webs] and their feathers get entangled," he said. "The more they struggle, the more tangled up and exhausted they get and they go into stress."

Associate Professor Ron Atkinson, who created the Find-a-Spider guide for Australian spiders, confirmed that the Golden Orb Weaver spider (Nephila pilipes) was "very efficient at catching insects". “Their venom quickly immobilizes insects, but it is unlikely it is potent enough to have any serious effects on humans, and I have never heard of anyone being bitten by one and certainly not anyone who was made ill as a result of such a biting," he said.

The Golden Orb Weaver spins a strong web high in protein because it depends on it to capture large insects for food, unlike funnel web and wolf spiders that actively hunt their prey. Another species called the bird-eating spider does not actually eat birds. "If a spider gets a bird, it’s a very lucky spider," Mr Czechura said.


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