Desperate female spiders fight by different rules

June 05, 2010

Durham, NC - If you thought women's pro wrestling was a cutthroat business, jumping spiders may have them beat.

In most animals the bigger, better fighter usually wins. But a new study of the jumping spider Phidippus clarus suggests that size and skill aren't everything - what matters for Phidippus females is how badly they want to win.

Found in fields throughout North America, nickel-sized Phidippus clarus is a feisty spider prone to picking fights. In battles between males, the bigger, heavier spider usually wins. Males perform an elaborate dance before doing battle to size up the competition. "They push each other back and forth like sumo wrestlers," said lead author Damian Elias of the University of California at Berkeley.

This fancy footwork allows males to gauge how closely matched they are before escalating into a full-blown fight. "Males rarely get to the point where they solve things by fighting," said co-author Carlos Botero of the National Evolutionary Synthesis Center in Durham, NC. "Before the actual fight there's a lot of displaying. This allows them to resolve things without injuring themselves."

But when the researchers watched female fights, they found that females fight by different rules. They skip the preliminaries and go straight for the kill. "Males have a more gentlemanly form of combat, whereas in females it's an all-out fight," said Elias. "At the drop of a hat they start bashing and biting each other."

And unlike male combat, female feuds were often fatal. "They don't give up, even when their opponent is beating them to a pulp," said Botero. "They keep going until one of them is dead, or severely injured."

The researchers were unable to predict which female would win based on size or strength. "Nothing we could measure predicted which one would come out on top. That was really unexpected," said Elias.

At first, the researchers wondered if victory went not to the bigger fighter, but to the owner of the battlefield. "In a lot of animals one of the things that determines whether they win a fight is whether they're on their own territory," Elias said.

Phidippus clarus spiders live in nests they build from silk and rolled up leaves. While males are nomads, wandering from nest to nest in search of mates, females generally stick to one nest and guard it against intruders.

To test the idea that in turf wars the rightful owner typically wins, the researchers set up a series of fights between resident and intruder females. But when they put pairs of females in an arena -- one with a nest, and one that was homeless -- the head of the household wasn't always the winner. Instead, the female most likely to win was the one closer to reproductive age.

"The ones that were closer to maturation fought harder," said Botero. "They were more motivated and valued the nest more strongly."

Why might that be?

Before a spider is ready to reproduce, she must first shed her hard outer skin and grow to adult size through a process known as molting. "They're very vulnerable to predators at that time," said Elias. "If they're really close to molting and they don't have a nest at that moment, they're unlikely to survive."

Females need the safety of their nests to molt, mate, and rear their young. "Finding a good nest becomes more critical the closer they are to maturing," said Elias.

"In female fights it's not how big or heavy they are, but how badly they want it," he added. "That trumps size and weight and whether it's her territory. They fight until they have nothing left."

The team's findings were published online in the June 4 issue of Behavioral Ecology.
-end-
Other authors on this study include Maydianne Andrade of the University of Toronto, Andrew Mason of the University of Toronto, and Michael Kasumovic of the University of New South Wales.

CITATION: Elias, D., C. Botero, M. Andrade, A. Mason, and M. Kasumovic. (2010). "High resource valuation fuels 'desperado' fighting tactics in female jumping spiders." Behavioral Ecology. doi:10.1093/beheco/arq073

The National Evolutionary Synthesis Center (NESCent) is a nonprofit science center dedicated to cross-disciplinary research in evolution. Funded by the National Science Foundation, NESCent is jointly operated by Duke University, The University of North Carolina at Chapel Hill, and North Carolina State University. For more information about research and training opportunities at NESCent, visit www.nescent.org.

National Evolutionary Synthesis Center (NESCent)

Related Spider Articles from Brightsurf:

Tapping secrets of Aussie spider's unique silk
The basket-web spider, which is found only in Australia, has revealed it not only weaves a unique lobster pot web but that its silk has elasticity and a gluing substance, that creates a high degree of robustness.

A new species of spider
During a research stay in the highlands of Colombia conducted as part of her doctorate, Charlotte Hopfe, PhD student at the University of Bayreuth, has discovered and zoologically described a new species of spider.

Flies and mosquitoes beware, here comes the slingshot spider
Running into an unseen spiderweb in the woods can be scary enough, but what if you had to worry about a spiderweb - and the spider - being catapulted at you?

Spider monkey groups as collective computers
New research shows that spider monkeys use collective computation to figure out the best way to find food.

Spider silk made by photosynthetic bacteria
A research team in Japan reported that they succeeded in producing the spider silk -- ultra-lightweight, though, biodegradable and biocompatible material -- using photosynthetic bacteria.

Spider silk can create lenses useful for biological imaging
Spider silk is useful for a variety of biomedical applications: It exhibits mechanical properties superior to synthetic fibers for tissue engineering, and it is not toxic or harmful to living cells.

Spider baby boom in a warmer Arctic
Climate change leads to longer growing seasons in the Arctic.

Spider combs tame unruly nanofibers (video)
Cribellate spiders spin thousands of tiny nanofibers into sticky threads.

New study reveals a life aquatic for many spider species
Researchers at the California Academy of Sciences and William Paterson University found that nearly one fifth of all spider families are associated with saltwater or freshwater aquatic habitats.

The mathematics of prey detection in spider orb-webs
Spider webs are one of nature's most fascinating manifestations. Many spiders extrude proteinaceous silk to weave sticky webs that ensnare unsuspecting prey who venture into their threads.

Read More: Spider News and Spider Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.