Rain can spoil a wolf spider’s day, too

Researchers at the University of Cincinnati found that wolf spiders can’t signal others or perceive danger from predators as easily on rain-soaked leaves compared to dry ones. Even communicating with would-be mates is harder after it rains.

The study was published in the Journal of Insect Behavior.

The spring nesting season coincides with the spiders’ mating season. Male wolf spiders are especially vulnerable to birds when they try to woo a mate with a flashy display, which involves drumming their exaggeratedly furry front legs on the leaves in front of them.

The UC study found that male spiders become motionless and “freeze” when a blue jay calls nearby. And they stay frozen longer on dry leaves than on wet ones, possibly because the dry leaves provide a better early warning than wet ones that dampen vibrations.

Uetz said the striped black and brown spiders have remarkable camouflage when they remain motionless.

“If they remain still, they just disappear,” he said.

“Like lots of predators, blue jays are visually oriented,” Uetz said. “They’re very visually acute. For them, movement really is the key.”

With climate change increasing the frequency and duration of spring rains, wolf spiders will face increasing ecological challenges, Uetz said.

“Spring is coming a little earlier. What we’re seeing is there’s a shift in the life cycle of the spiders,” Uetz said. “If global warming shifts the annual life cycle of the spiders, that will push them out of synchrony with the nesting season of the birds, which is more closely tied to daylight cues.”

Wet leaves didn’t discourage male spiders from courting females. Male spiders increased visual signaling to compensate for the inability to use vibrations. But spiders that could use dry leaves to communicate to females had more mating success. 

UC graduate Rachel Gilbert, a study co-author, said spiders can be important bellwethers of environmental change.

“Spiders are very important to local ecosystems, both as a predator of insects and as a major food source to larger animals like birds,” she said. “Understanding how to predict and mitigate ecosystem imbalance caused by the disruption of prey behavior due to climate change is critical.”

The study was funded by grants from the National Science Foundation.

Many of the paper’s eight co-authors conducted their research as undergraduates in Uetz’s lab. This experience can have a profound effect on a student’s academic trajectory, Uetz said.

When he was an undergraduate, his first research project helped him overcome a fear of spiders.

“Most people who study spiders will say they had a lifelong fascination with them — but not me,” he said. “I was five or six playing cops and robbers and put my hand at the bottom of a gutter downspout and a spider ran up my arm and I totally freaked out.”

Uetz took invertebrate zoology and biology classes from his mentors, Albion College professors Dean Dillery and Alan Brady. His fear of spiders turned into fascination.

“You model yourself off your mentors. Dean Dillery encouraged me to do research. And when it was done, he took me to an Entomology Society meeting in Lansing, Mich., to give a presentation. It was a really meaningful experience, so I try to do the same with my students,” he said.

More scientific organizations are offering opportunities to undergraduates to present research, he said. Uetz took several undergraduates to the Arachnological Society conference last year at Cornell University.

“When I started undergraduate research in the lab, I had no interest in pursuing a research career,” Gilbert said. “But by the end, I decided to ask if I could stick around and pursue a graduate degree in Dr. Uetz's lab.”

Today, she has a doctorate from UC and works as a data scientist at NASA.

“I think the benefit of undergraduate research is that you get a new perspective into how scientific research is done and you gain skills that can be applied to other careers,” she said.

Featured image at top: UC biologists discovered that rain can interfere with spider communication. Photo/Joseph Fuqua II/UC