Climate change may be making spiders more aggressive, are humans next?

Scientists recently discovered that climate change related hurricanes are making spiders act more aggressively.
Image: Wikimedia Commons | Judy Gallagher

Understanding the way that climate change affects the smallest social systems can say a lot about the wider implications of the crisis. A recent study has found that a certain species of spider living on the Gulf of Mexico and Southern Atlantic coasts of the U.S. has responded to the climate change intensified hurricane seasons by becoming more aggressive, as reports.

Jonathan Pruitt of McMaster University in Ontario led the study published in Nature Ecology and Evolution. He and his team analyzed the behavior of a species of spider called Anelosimus studiosus. They studied the spider in areas affected by Tropical Storm Alberto and Hurricanes Florence and Michael. Pruitt and his team discovered that the storms acted as a form of natural selection. This “survival of the fittest” event seemed to select more aggressive spiders over docile ones.

Warriors & Nannies

A. studiosus is a small, tangled web spider that is much more social than most arachnids. Most spiders are lone wolves so to speak. On the contrary, A. studiosus cohabitates in groups of up to several hundred females. In an earlier study, researchers found that these colonies are usually dominated by docile “nannies” and more aggressive “warriors.”

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When resources are plentiful, the level of aggression in the spider species doesn’t seem to affect the group as much. But, when resources grow scarce, as they might after a hurricane, the aggressive spiders had an edge.

Related: What lifeforms might and might not survive climate change?

Pruitt devised an ingenious method to study the aggression levels of A. studiosus. First, the intrepid scientist wrapped a mechanical toothbrush in wire. He then used it to poke a piece of paper into the spiders’ webs. He found that many of them couldn’t resist the fluttering, insect-resembling pieces of paper. However, some of the spiders tended to hang back. These, Pruitt labeled docile, while the ones that went for the paper were classified as aggressive.

In this way, the team studied 240 spider colonies both before and after the three storms mentioned above. The researchers also observed spiders in areas not hit by storms. They found that regardless of intensity, size, and storm duration, more aggressive groups proved more likely to produce egg sacks. Moreover, the offspring of aggressive groups tended to have higher survival rates than their peaceful counterparts. In areas not affected by the storms, the docile groups continued to dominate.

‘Behavioral Tipping Point’

If the current trend of climate change intensified storms continues, Pruitt posits that A. studiosus could begin to become more like their lone wolf cousins. “There’s a behavioral tipping point when very very aggressive colonies stop working together, start killing each other, and the group wisely disbands,” he told Inverse. “Combine hurricane increases with global warming and I think you could get something like that.”

Dartmouth biologist Matthew P. Ayres, who didn’t take part in the study, sees the implications of Pruitt and his team’s study in “much broader” terms. In other words, it’s not just spiders but also other animals and plants that could be affected by climate-linked extreme weather events.

As the climate crisis continues to deplete human resources, it would be appropriate for humanity to take heed of Pruitt’s study on spider aggression, especially the “behavioral tipping point” wherein the spiders start killing each other. Humans are aggressive enough, which is all the more reason to seriously address the climate crisis before it is too late.