A new study of the jumping spider Phidippus clarus has found that fighting for female jumping spiders of this species is an extremely serious matter. It is not quite as serious for males. In battles between males, the bigger, heavier spider usually wins. Males also 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.
Co-author Carlos Botero of the National Evolutionary Synthesis Center in Durham, NC says the displaying often helps the male spiders "resolve things without injuring themselves."
Female spiders are all business when they battle and the battle is not over until one of the spiders is dead or seriously injured. The researchers found that what matters for Phidippus females in fighting is how badly they want to win. Females go straight for the kill. Damin Elias says, "At the drop of a hat they start bashing and biting each other." Botero adds that the feuds often end in death. "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."
The researchers set up a series of fights between resident and intruder females. They found that the female spiders closer to maturation fought harder. The researchers theorized that this is because spiders close to reproduction have to first shed their skin, which leaves them vulnerable to predators. Elias says, "They're very vulnerable to predators at that time. If they're really close to molting and they don't have a nest at that moment, they're unlikely to survive."
Photo of a female of the Jumping Spider, Phidippus clarus by Damian Elias