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Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things


Wild Things

Delicate spider takes down tough prey by attacking weak spots

Loxosceles gaucho recluse spider

The Loxosceles gaucho recluse spider (left) can kill a heavily armored Mischonyx cuspidatus harvestmen (right) by disabling its weak spots, a new study finds. Here the spider is inflicting a long bite to a joint on the harvestman’s third leg.

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Like a miniature martial artist, the Loxosceles gaucho recluse spider can sneak up on a heavily armored harvestman (a type of arachnid), identify its weak spots and quickly disable its meal, a new study reveals.

This species of recluse spider lives in and around Sao Paolo, Brazil. Often the spiders are found near and inside people’s homes, dwelling under tree trunks, dead palm fronds and bricks. They eat a variety of arthropods, including crickets and Mischonyx cuspidatus harvestmen.

Harvestmen aren’t typical meals for such delicate-bodied spiders because their thick cuticle has only a few spots, such as their joints, that would be vulnerable to a spider’s bite. But after finding dead harvestmen on L. gaucho spiders’ webs, Julio Segovia of the University of Sao Paolo and colleagues suspected that the spiders somehow overcome the harvestmen’s defenses.

The researchers came up with a series of hypotheses about how the spiders might accomplish the feat: The spider tracks down a harvestman via chemical cues. It detects its prey through vibratory cues. And the spider’s web helps it handle the harvestman so that it can bite the arachnid in its vulnerable spots. The researchers tested each of these hypotheses and reported their findings in the March Animal Behaviour.

First, they put hungry spiders into an arena with one spot that had chemical cues from harvestmen and another with chemical cues from crickets. The spiders had no preference for either one. Nor did the spiders prefer either of the cues over that of a blank piece of paper. So scent is probably not leading them to a meal.

The scientists next tested the spiders’ ability to sense vibrations by letting them prey upon harvestmen on paper and on granite. There was no difference in the spiders’ hunting ability — so they’re probably not using vibrations to sense their prey. And in a test of the third hypothesis, the presence of silk had no effect on the spiders’ ability to capture the harvestmen; that hypothesis was wrong as well.

The behavior of the harvestmen during tests was unusual, as well. “Harvestmen have a pair of scent glands used to repel predators,” notes study coauthor Rodrigo Hirata Willemart of the University of Sao Paolo. “It came as a surprise that these harvestmen did not release their smelly secretions against a predator with such a high success in eating harvestmen.”

Videos of the spiders finally revealed their hunting strategy: The spider spots a harvestman and then approaches or brushes by its prey. At that time, the spider is probably identifying weak spots to attack. Then it delivers a series of short and/or long (up to several minutes long) bites until the harvestman stops trying to get away. Finally, the spider weaves silk threads around its meal.

“Sometimes the harvestmen freeze,” Willemart says. “Sometimes they attempt to scurry away. But the spider is faster and quickly manages to move and stay in front of him. The harvestman goes right, the spider goes right, always in front of the prey.”

The recluse spider can disable a cricket faster and with fewer bites, probably because that insect lacks the harvestman’s heavy armor and require less venom to subdue, the scientists note. That may explain why earlier researchers reported finding more crickets than harvestmen in the spiders’ webs — the crickets are the easier meal.

Animals,, Evolution

Cringe away, guys — this spider bites off his own genitals

By Sarah Zielinski 7:00am, January 20, 2015
After sex, a male coin spider will chew off his own genitals, an act that might help secure his paternity.
Animals

Lemurs aren’t pets

By Sarah Zielinski 4:05pm, January 16, 2015
The first survey of lemur ownership in Madagascar finds that thousands of the rare primates are held in households.
Animals

Paternity test reveals father’s role in mystery shark birth

By Sarah Zielinski 1:13pm, January 13, 2015
A shark pup was born in a tank with three female sharks but no males. A genetic study finds that the shark must have stored sperm for nearly four years.
Animals

How many wildebeest? Ask a satellite

By Sarah Zielinski 1:11pm, January 8, 2015
High-resolution satellite imagery could offer a reliable way to count large mammals in open habitats from space.
Animals

Little African cats need big parks

By Sarah Zielinski 9:19am, January 6, 2015
Protecting African wildcats requires large protected areas free of feral cats to avoid the risk of the wild species disappearing through hybridization.
Animals

China’s reindeer are on the decline

By Sarah Zielinski 9:00am, December 24, 2014
A small, semi-domesticated population of reindeer found in northern China is suffering due to threats ranging from inbreeding to tourism.
Animals

Starving mantis females lie to make a meal of a male

By Sarah Zielinski 9:02am, December 22, 2014
When in desperate straits, a female false garden mantid turns into a femme fatale, emitting false chemical cues that lures in a male to eat.
Animals,, Evolution

The dinosaurs in the backyard

By Sarah Zielinski 8:30am, December 16, 2014
Chickens are some of the closest relatives of dinosaurs, and though genetic tinkering the birds might even one day be turned into tiny dinos.
Animals

Australia’s unexpectedly dangerous creatures

By Sarah Zielinski 8:28am, December 12, 2014
Australia is home to an array of deadly things — from crocodiles to venomous snakes — but dangers can also be found among seemingly safe critters.
Animals

That puffed-up pufferfish isn’t holding its breath

By Sarah Zielinski 3:30pm, December 8, 2014
Pufferfish can breathe just fine even when they puff themselves out with water, a new study finds.
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