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Hurricanes may spin a more aggressive population of spiders, new study shows

The study suggests storms make spiders more active in protecting their nests, and they pass the trait down.
New research shows that the more aggressive the Anelosimus studiosus spider is, the better chance they’ll survive a hurricane. [Special to the Miami Herald] [Special to the Miami Herald]
Published Aug. 22
Updated Aug. 22

This story was written by Alex Harris, climate change reporter for the Miami Herald.

If you live in Florida, you know the psychological toll hurricanes have on humans. We panic, we obsess over the latest weather report, we rant about horrendous evacuation traffic.

What’s far less known is the effect of hurricanes on non-human residents. One new study shows storms have a surprising evolutionary impact on spiders — producing a more aggressive population of arachnids.

That’s the conclusion of a paper published Monday in Nature Ecology & Evolution, which found that aggressive spider colonies survive and reproduce better after storms than docile ones, a finding based on a series of storms that made landfall in Florida and Georgia. The study is part of an emerging field of research aimed at understanding how climate change can alter the way wildlife and bugs evolve. Another hurricane-specific study last year found that lizards with longer legs do a better job of surviving hurricanes.

“The impact of these storms on wildlife are mostly a big question mark on our white board,” said one of the paper’s authors, Jonathan Pruitt. “Hurricanes could be shaping that evolutionary history of animals and we don’t even know.”

New research shows that the more aggressive the Anelosimus studiosus spider is, the better chance it will survive a hurricane. Their cobwebby nests can be anywhere from golf ball sized to basketball sized. [Special to the Miami Herald] [Special to the Miami Herald]

Predicting where storms will hit (and getting there in enough time to collect usable data) is difficult work. It’s part of the reason why scientists say research on the evolutionary impacts of hurricanes on specific wildlife populations is challenging. Most studies tend to focus on mortality or habitat loss — the immediate aftereffects.

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The latest study from Pruitt — research chair in the department of psychology, neuroscience and behavior at McMaster University in Ontario, Canada — focused on how one type of bug adapts and survives.

The study included data from three 2018 storms, Tropical Storm Alberto, Hurricane Florence and Hurricane Michael, with most of the research spots in Florida. In each case, Pruitt had to try to predict where a storm would hit and rush over to find out what the spider population was like before a storm. Then he’d wait it out in a hotel room for a couple of days before heading back out in his F-150 truck to check on his spiders.

“The largest bugaboo about this research is coming back to these sites after the storm,” Pruitt said. Luckily, the Floridians and Georgians he ran into were happy to break out their chain saws and carve him a path to the spiders.

Pruitt focused the research on Anelosimus studiosus, a tiny, saffron-colored spider with a ruffled pattern on its globe-shaped behind that lives in the Eastern U.S. He called them “junk spiders” that make their cobwebby nests, which can be anywhere from golf ball-sized to basketball-sized, over water.

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How can you tell if a spider is more aggressive? You use “a vibrating narwhal,” as Pruitt puts it.

“Traditionally we use a vibrator, but for this I used a mechanical toothbrush,” he said.

He wrapped the toothbrush in wire until it had a point sticking out (like a narwhal horn) that he used to gently poke a piece of paper he stuck to the spider web, making the paper flutter like a trapped insect.

“The spiders find that irresistible,” said Pruitt.

If the spiders rushed out to defend their web immediately, Pruitt called them aggressive. If they hung back a bit, he categorized them as docile. He found that areas that were often hit by storms had more aggressive spider populations, compared to less vulnerable areas. Those aggressive spiders did a better job of having babies and keeping those babies alive — making hurricanes a form of natural selection favoring more combative arachnids.

One of the first studies to talk about the impact of hurricanes on wildlife was published in Nature last summer. It involved lizards — and a leaf blower.

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Lizards with longer arms and bigger toe pads, researchers found, were more likely to survive the hurricanes that battered Turks and Caicos in 2017. In a case of making lemonade out of lemons, the researchers from Harvard University and the Paris Museum of Natural History didn’t originally intend to study the effects of storms on the local lizard population, but Hurricanes Irma and Maria changed their plans, said one of the authors, Harvard post-doctoral fellow Colin Donihue.

Researchers found that long-legged lizards with bigger toepads survived hurricanes better than their short-legged brethren. [Special to the Miami Herald] [Special to the Miami Herald]

“A really novel twist to Jonathan’s study is he actually went down and anticipated where hurricanes were going to hit and went down and got the data,” he said. “My data collection was entirely serendipitous.”

Donihue and his team wrapped up their initial research four days before Hurricane Irma hit in September, which was quickly followed by Hurricane Maria. That’s when they decided to come back six weeks later and see what happened to the lizards.

The end of the field work left them with plenty of questions and no guarantee of another storm, so the scientists decided to rig up a high-powered red leaf blower and a camera to capture exactly what happens when these lizards encounter high winds.

The result: riveting photos and videos of the tiny reptiles hanging on for dear life, and a better understanding of how they survive hurricane force winds.

“There’s really been very few studies that document any non random mortality or natural selection,” Donihue said. “It’s something we just completely overlooked, well, forever.”

The work done by Donihue’s team has set off “a little flurry of interest” among other scientists, he said. They’re all trying to find out the evolutionary impacts of hurricanes, especially as research shows climate change could be making storms stronger. He and Pruitt are both continuing to research what happens to wildlife after storms, and they hope other scientists will too.

“Extreme climate events, hurricanes specifically, could have really important consequences for all the species on the planet and not just as mortality events but as readjustment to evolutionary trajectories,” Donihue said. “As hurricanes become more severe in the future it could have an even more severe impact than we know of now.”

This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the South Florida Sun Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.


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