“This study provides some new insight into the age-old question of why males go to such ridiculous lengths to impress females,” said UF/IFAS entomologist Lisa Taylor.
Credit: Courtesy, Lisa Taylor, UF/IFAS
Male jumping spiders will try to mate with any female, but that lack of discretion could cost them their lives, says a University of Florida Institute of Food and Agricultural Sciences researcher.
“We think that one reason these displays have evolved in male jumping spiders is to compensate for the fact that they can’t tell females of closely related species apart,” Taylor said. “Males run around courting everything that looks remotely like a female, and they place themselves at a very high risk of cannibalism from hungry females of the wrong species who have no interest in mating with them.”
For the study, scientists searched for spiders along the shores of a river in Phoenix, Arizona. When they found one, they watched and recorded everything it did, using a voice recorder. If it was a male, they monitored how many other females he encountered, which species and whether or not he tried to court them. If it was a female, they recorded how many males and which species tried to court her. They also recorded whether males were attacked or eaten by females.
Taylor thinks that a male’s colorful courtship dance allows him to identify himself to a female from a safe distance. These displays likely allow females to tell the males of different species apart. Then females can decide what action to take while the male is still a safe distance away.
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“This study provides some new insight into the age-old question of why males go to such ridiculous lengths to impress females,” Taylor said.
In jumping spiders, the answer might be that these colorful displays let males identify themselves to females without being eaten.
The females of many species look a lot alike, and males don’t seem to have a good way to tell them apart. But the males of most jumping spider species look different from one another, so females make the decisions. The male strategy seems to be to court anything that looks remotely like a female and hope for the best, Taylor said.
Jumping spiders are commonly found in residential backyards, and most people don’t even know they’re there, Taylor said, much less that the male spiders are singing and dancing.
“People might be interested to know that their yard is teeming with confused, but adorable, male jumping spiders that are running around singing and dancing for every female in sight and that these males spiders are pretty clueless about how to find the right species of female,” she said.
The study is published in the online journal PLOS ONE.
Economies of scale
Time-of-flight imaging essentially turns one measurement — with one light pattern — into dozens of measurements, separated by trillionths of seconds. Moreover, each measurement corresponds with only a subset of pixels in the final image — those depicting objects at the same distance. That means there’s less information to decode in each measurement.
In their paper, Satat, Raskar, and Matthew Tancik, an MIT graduate student in electrical engineering and computer science, present a theoretical analysis of compressed sensing that uses time-of-flight information. Their analysis shows how efficiently the technique can extract information about a visual scene, at different resolutions and with different numbers of sensors and distances between them.
They also describe a procedure for computing light patterns that minimizes the number of exposures. And, using synthetic data, they compare the performance of their reconstruction algorithm to that of existing compressed-sensing algorithms. But in ongoing work, they are developing a prototype of the system so that they can test their algorithm on real data.
Lisa A. Taylor, Erin C. Powell, Kevin J. McGraw. Frequent misdirected courtship in a natural community of colorful Habronattus jumping spiders. PLOS ONE, 2017; 12 (4): e0173156 DOI: 10.1371/journal.pone.0173156