Female spiders fight 'like sumo wrestlers'

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Washington, June 8 (ANI): A new research has shown that while the males of a jumping spider species merely threaten and posture instead of actually fighting each other, fights among females are often fatal.

In most animals the bigger, better fighter usually wins. But the 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.

Co-author Carlos Botero of the National Evolutionary Synthesis Center in Durham, NC, said: "Males rarely get to the point where they solve things by fighting. 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.

Elias said: "Males have a more gentlemanly form of combat, whereas in females it's an all-out fight. 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. They keep going until one of them is dead, or severely injured," said Botero.

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.

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

Elias said: "In female fights it's not how big or heavy they are, but how badly they want it. 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 Behavioural Ecology. (ANI)

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