Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=177313
Story Retrieval Date: 5/19/2013 4:10:00 AM CST
Courtesy of George Uetz, University of Cincinnati
Just as tennis player Roger Federer adjusts his game based on a clay, grass or hard court venue, male wolf spiders change their seduction strategies when courting a female on different surfaces.
To attract a female, a male performs a body-bumping, toe-tapping dance that creates vibrations sent through the forest floor or mossy rock he may be using as a stage. Males will also raise up their bristled forelegs as a visual signal. Success for a suitor is based on the combination of these actions.
“He’s like a one man band playing percussion and the washboard,” said George Uetz, biological sciences professor at the University of Cincinnati, who researched this behavior.
Wolf spiders do not build webs. They generally live on the forest floor and prey on small insects anything in the right size, even other small spiders, according to Petra Sierwald, associate curator at the Field Museum in Chicago.
The spider, Shizococosa orcreata, has the capacity to detect, discriminate, and evaluate other spiders, insects, environmental cues and predatory threats using multiple senses and integrate this information, according to Uetz.
“This makes them a great model for understanding interactions between the physical and biological environment,” Uetz said.
Researchers observed the wolf spiders on a variety of substrates that naturally occur in their environment: Leaf litter, stone, soil and wood. The males that showcased their dance of seduction on leaf litter doubled their chances of securing a mate compared with males courting on the other surfaces.
“We’ve learned that the physical environment of the spiders’ habitat in the forest floor affects detection and discrimination of male signals by females,” Uetz said.
Uetz and co-author Shira Gordon, of the University of Strathclyde in Scotland, measured the vibrations with a laser vibrometer. The good vibrations created by the dance of love on leaf litter offered the highest vibratory signals suggesting leaves provide the best mode of communication for the males to entice the females.
When given the option of a leaf, stone, soil or wood surface to occupy, the males visited the leaf for longer periods of time. The results suggest that males recognized the different substrates and chose the one that could enhance their chances of a successful mating, according to Uetz.
Males produced about the same amount of body vibrations on each substrate, despite the fact that leaf litter transmitted the seismic signals best. However when the males were trying to seduce the females on non-leaf surfaces, they compensated with a more visual spectacle for the contemplating ladies.
“The males recognized the different substrates, and when on those [substrates] that dampen vibration, they have the capacity to shift signal modes,” Uetz said. “This level of flexibility in courtship behavior is unusual for an invertebrate animal.”
Uetz plans to continue researching the relationship between communication signals and behavior in spiders. One area he wants to look at is whether competing male spiders might be “eavesdropping” on the males’ conspicuous courtship of females.
“Basic research in this area may ultimately provide insights that lead to applications in robots and technologies associated with signal detection and processing, as well as certain aspects of human health,” Uetz said.