By Jordan Bush
While on a moonlit stroll through the rainforest of the Tambopata Nature Reserve in southeast Peru, you mustn’t trip over the cluster of physicists and engineers blocking the path.
When the weather is dry and their equipment is charged, they flock, mesmerized, around a seemingly empty tree. Step around them carefully – avoid any sudden movements. They are a jumpy crowd. They are flanked by high-speed cameras, lasers, acoustic sensors, and a portable floodlamp. They snap their fingers at the bush, chatter to each other excitedly, and give sporadic cheers.
They would forgive you if you think they are crazy.
But as you edge around, take a moment to peer into the illuminated shrubbery. You may catch a glimpse of the objects of their attention: a small cone-shaped spider web, stretched tight by a tension line secured to a nearby stick, and a tiny spider, only millimeters across, perched motionless where web and line meet.
And if you are really lucky, if you squint and huddle close, you may see it – a passing insect, a leg flick, a spider shooting towards the hapless prey like a bolt from a crossbow, too fast for your eye to follow.
You may even cheer with them, this time.
After a viral video of their unusual behavior surfaced in 2014, slingshot spiders have become arachnid celebrities. They have been profiled by the likes of National Geographic, NPR, and Wired. Their claim to fame? They use webs to slingshot themselves at flying prey.
Yet while academic and internet communities have been fascinated by slingshot spiders for years, they are hard to find and even harder to study, rendering the mechanisms of their slingshots largely unknown.
Fortunately, Dr. Saad Bhamla, assistant professor in the School of Chemical and Biomolecular Engineering at Georgia Tech University, has never been one to back down from a challenge. Bhamla and his colleagues are among the first researchers to travel to the elusive spider’s natural habitat to study their charismatic slingshot.
As a biophysicist, Bhamla is interested in how small organisms from across the tree of life use specialized structures to generate faster movements, harder punches, and stronger bites.
“Our lab works on asking how tiny organisms, whether it’s single cells or arachnids, can achieve really really high accelerations using springs and latches,” Bhamla says.
Bhamla first became interested in slingshot spiders during a trip to South America as a postdoc studying leafcutter ants. When he learned of the scarcity of research on their slingshotting behavior, he knew he wanted to be the one to study the spiders’ super-fast launching technique.
“I have a special fondness for all kinds of insects, tiny critters, single cells – things that you may walk past and not even know are there but sustain a whole ecosystem,” he says.
So armed with optimism, an expertise in biomechanics, and very little field experience, Bhamla’s group traveled to the Peruvian rainforest in 2018 to conduct the first official study of the slingshotting behavior of the minuscule spiders.
A trip founded on a mixture of “ignorance and naivete,” Bhamla laughs.
And this was not your mamma’s fieldwork. The Tambotata Research Center is one of the most remote lodges in South America. Just getting there involves two plane rides and a six-hour boat trip. Once there, the researchers’ two- to four-hour hikes had to be squeezed between frequent rainstorms (slingshot spiders do not like rain) and the limited hours they could charge their equipment each day.
“There’s a reason no one has studied them in 30, 40 years,” Bhamla says. “It’s inaccessible.”
Finding the spiders was another problem. Most species of slingshot spiders are so tiny they are hard to see with a naked eye, and the South American species live in one of the most densely foliated and biodiverse areas in the world. Many species are also only active at night, further complicating the process.
The secret, Bhamla says, is the phenomenal local guides working at the station. Jaime Navaro, the naturalist who worked with Bhamla’s group, showed the researchers how to look for the distinctive cone-shaped spiderwebs in the undergrowth.
“[He was] an encyclopedia of walking knowledge,” Bhamla says. “He deserves the credit.”
The group’s focus on biomechanics, which requires three-dimensional video data, made an already difficult study organism even harder to work with. Slingshot spiders will not build webs in captivity, meaning that the researchers had to hike armloads of high-tech equipment into the rainforest each night to collect data on the spiders in the field.
“They are very picky about the structures they will build their webs on,” Dr. Symone Alexander, a postdoctoral researcher working with Bhamla’s group, says. “We had to get our video in their natural habitat.”
This work is only made possible by 21st-century technology. The spiders are so small, and move so fast, that most cameras can’t even register them. The group has to use high-speed cameras with such sophisticated lenses that it is “effectively bringing a microscope into the field,” Bhamla says. This equipment is so powerful it allows the researchers to see even the tiny leg movements of the 1-millimeter spiders.
“In the past, there weren’t these portable high-speed cameras,” Alexander says. “So [scientists] could make observations, but it wasn’t fast enough to understand how these spiders move.”
So… was it worth it?
Was the six-hour boat ride, the late nights, the four-hour hikes, the rain, the stress of protecting their expensive equipment from the rain, worth it in the end?
Bhamla’s eyes light up when he talks about their results.
Before their trip, many of the existing videos showed the spiders releasing their webs only after prey crashed into it, creating the prevailing hypothesis that the slingshot is a response to perturbations of the web. Yet Bhamla’s group was able to record videos of the spiders flinging themselves off the web to catch flying insects in midair – a completely different hunting strategy than most spiders.
“We have one of the first videographic evidences that – through unknown means, we don’t know how they sense, how they detect that a flying insect has come by – they will release and catch an insect in midair in less than 100, 150 milliseconds,” Bhamla says.
“To the best of our knowledge, this is the fastest full-bodied arachnid motion,” Alexander adds.
Bhamla and Alexander also found that, while the spiders didn’t always hit their mark, they exhibited remarkable control over their trajectories.
“Originally, it was thought that the legs fully released and that after they let go of that tension line, their control was pretty much over,” Alexander says. “But when we looked at it in the high-speed videos, [it was] actually a very fast, but a very fine-tuned motion.”
“They only opened their legs about 60 to 75 microns. So it’s small scale, its super-fast, and the spider actually only releases a small bundle of the silk that’s its pulled under its body with the tension line, so it has a lot more control than we originally thought.”
They even discovered two previously undescribed species of slingshot spiders, bringing the total number of species they recorded up to five.
Upon reflection, Alexander decides the biggest challenge of the trip wasn’t the remote conditions or the field logistics – it was trying not to get too excited.
“I’ve wanted to go to Amazon rainforest since I was a child,” she says. “So just being there and seeing all of the different things that were going on – it was hard to focus on actual work!”
She was so excited about her field adventure that she neglected to mention her arachnophobia to her team before they got there.
“I was like, ‘why didn’t you tell me earlier?!’” Bhamla laughs.
“Before this, I avoided spiders as much as possible,” Alexander admits. But once she got past her heebie-jeebies, the materials scientist in her became fascinated by the amazing properties of the slingshot spider’s tough yet elastic web.
“My academic research [is focused on] taking cues from nature to design materials that are multifunctional,” she explains. “Understanding how organisms are designing for survival.”
She now considers herself a spider ally, even rescuing household spiders that previously would have gotten squished. She is even considering incorporating spiders into future materials science research.
Bhamla cannot wait to continue working with slingshot spiders and has plans to go back to the Amazon later this year. In the meantime, he is working with collaborators at the Smithsonian and the University of Akron to conduct comparative studies with a more locally accessible slingshot spider species found in Georgia and Ohio.
After traveling to the ends of the Earth for his first project, he will now be able to study his super-fast arachnids from the comfort of his own backyard.