For a tiny Australian spider, somersaults are the secret to dealing with an ant twice as big.
Ants – Armed powerful jaw Sometimes chemical weapons – so dangerous for spiders that less than 1% of arachnids try to hunt these insects (SN: 9/8/21). High-speed footage now shows Australian ant killer spiders (Gardenia) can deal with this dangerous prey by jumping over and wrapping the victim with silk.
hunting action Not found in any other spider speciesthe researchers reported on September 19 in Proceedings of the National Academy of Sciences.
“This acrobatic act is fascinating. I’ve never personally seen this hunt,” said Paula Cushing, an evolutionary biologist and curator of invertebrates at the Denver Museum of Nature and Science, who was not involved in the study.
Alfonso Aceves-Aparicio, a behavioral ecologist at the Max Planck Institute for Chemical Ecology in Jena, Germany, came across the somersaulting spider on his way home one night. Aceves-Aparicio, then a graduate student at Macquarie University in Sydney, was intrigued when he noticed dark spots on the pale bark of a eucalyptus tree.
The dots are tiny spiders that move among the ants. Suddenly, one of the spiders jumped up. “I thought it was trying to escape an ant,” recalls Aceves-Aparicio. “But then I saw the ants floating around and I thought, wow, what’s going on here.”
Aceves-Aparicio borrowed a high-speed camera to get a more detailed look at what the spiders were doing. By slowing down, he and his colleagues could see that the spiders were actually hunting the ants in a completely unknown way.
Most ant-hunting spiders use webs or sneak up on their prey from behind to minimize risk. But, despite being smaller than their prey, Aceves-Aparicio’s spiders face banded sugar ants (bowback) head on. Each spider positions itself so it can watch the ants as they climb the tree. When a person approaches, the spider flips over its prey. After flying into the air, the spider tethers a silk thread to the ant.
This single tethering action—performed in milliseconds—determines whether the hunt will be successful or not. If the tether gets stuck, the spider sprints around the ants, subtly surrounding them with more silk, before pulling them off their feet, dragging them away and eating them.
What Aceves-Aparicio and his colleagues stand out most is the effectiveness of the technique. Predators like lions and wolves tend to miss about 50 percent of their intended targets. The 60 spider hunts the researchers filmed had a staggering 85 percent success rate.
For Aceves-Aparicio, the discovery shows that extraordinary behavior can be hidden in plain sight. “The message here is to have a little curiosity and focus,” he said. “There are things going on everywhere. We just have to find them there.”