The extravagant courtship dance of wolf spiders made them an easy mark for birds and other predators as suspected by a biologist from the University of Cincinnati, George Uetz. However, it was only when Uetz and his colleague Dave Clark from Alma College teamed up with former University of Minnesota researcher, Tricia Rubi, and her captive colony of blue jays that he could prove it.
The researchers published their findings in the journal Behavioral Processes where Rubi trained a captive colony of blue jays to peck at buttons to indicate whether or not they saw wolf spiders (Schizocosa ocreata) on video screens.
Clarke made videos superimposing images of courting, walking, and stationary male spiders on a leaf litter background. Rubi presented the videos to blue jays on a flat display screen on the ground. When viewed from above, the speckled black and brown spiders disappear amid the dead leaves.
The UC's Uetz noted that by courting the way they do, they are putting themselves at risk of bird predators.
Uetz explained that his lab studies the complementary methods spiders employ to communicate with each other called multimodal communication. Female spiders leave a pheromone trail behind them in their silk and when they rub their abdomens on the ground. When male spiders come into visual range, they bounce and rattle their legs on the leaf litter to create vibrations that can travel some considerable distance to the legs of potential mates. Also, the males wave their front legs in a unique pattern to captivate females.
According to the researchers, wolf spiders would freeze in place when they detected the sharp, loud calls of blue jays, cardinals and other insect-eating birds. By comparison, they ignored the calls of seed-eating birds like mourning doves along with the background forest noises like the creak of katydids.
Rubi explained that natural selection is the selection for survival, which would lead to spiders that are less conspicuous to predators. But the sexual selection is driven by females. And they select for a more visible display
As Rubi noted further, in genetic terms, fitness is measured in the number of healthy offspring produced. So, while staying by minimizing risk is a good strategy for the individual, it is not a viable strategy for the species.
Uetz opined that female wolf spiders could be quite selective about the qualities they value in a mate. The tufts on their forelegs are quite essential. Their size and symmetry play a significant role. They are so tiny and have brains the size of a poppy seed. It may be hard to think they discriminate, but they do. And at least for successful male wolf spiders living in a hostile world, this means love wins over fear.
