Scientists from the University of Cincinnati have directed research efforts in analyzing courtship dance of wolf spiders, in which the spiders wave their furry forelegs in the air. According to the study published in the journal, Behavioural Processes, this characteristic feature of the wolf spiders make them easy predators.
In order to confirm the hypothesis, researchers trained a captive colony of blue jays. As a part of the research process, Dave Clark from the University of Minnesota created videos of male spiders, with images of them courting, walking, including pictures of stationary spiders. These were superimposed on leaf or litter background and then presented to bird species through a flat screen placed on the ground. The blue jays pecked at buttons, which signaled the scientists on whether they spotted wolf spiders on the video screen.
The result of the study confirmed that blue jays faced difficulties in identifying spiders that were motionless, a characteristic adaptive value, termed as “freeze behavior”. Moreover, when viewed from the top, the spiders disappeared in the camouflage of dead leaves. The experts also alleged that birds could not spot spiders that walked but were especially quick to detect spiders that were engaged in courtship behavior. This feature of the spider makes them vulnerable to predators.
The study also analyses the distinctive communicative patterns of the spiders. The female spiders allegedly rub their abdomens on the ground, leaving behind a trail of silk. In the vicinity of male spiders, they bounce on leaf litter, vibrating the surface, and thus attracting the attention of potential male spiders. On the other hand, male spiders wave their legs to lure mates.
Wolf spiders carry a chemical called taurine, nourishment which makes them attractive and tasty to the birds. The wolf spiders used the freezing mechanism to save themselves from the bird predators. “Birds are super visual. They have excellent color vision and good visual acuity. It’s not surprising they would have no trouble seeing spiders in motion,” one of the research experts commented.
The experts especially adhered to the question that if natural selection meant courting spiders were more vulnerable to have preyed, why did this characteristic feature of the spiders prevail among generations. According to experts, this feature of the spiders was driven by another selective force.
“Natural selection is a selection for survival, which would lead to spiders that are less conspicuous to predators,” she said. “But the sexual selection is driven by females. And they select for a more conspicuous display.” Moreover, the researchers shed light on another characteristic of the female spiders, denoting that they were very selective about their male counterparts. “The longest-lived male can still have a fitness of ‘zero’ if he never mates. So there appears to be a trade-off between being safe and being sexy. That balance is what shapes these courtship displays.”
The study concludes that in the world of spiders, love reigns over fear.