High-speed cameras have revealed the extraordinary hunting technique of the Australian ant-slayer spider, which is highly successful and thought to be unique
Life
19 September 2022
An ant-slayer spider subdues a crepuscular banded sugar ant Alfonso Alceves
The ant-slayer spider of Australia has an extraordinary hunting technique that involves leaping over its much larger prey, high-speed photography has revealed.
“To our knowledge, it’s unique,” says Alfonso Aceves-Aparicio, who is now at the Max Planck Institute for Chemical Ecology in Germany.
While Aceves-Aparicio was at Macquarie University in Sydney, he noticed the unusual behaviour of ant-slayer spiders (Euryopis umbilicata) on trees on the campus at night.
“I saw an ant climbing on the tree trunk, and I saw something happening really fast,” Aceves-Aparicio says.
He initially tried filming the behaviour with his phone, but capturing all the details required a high-speed infrared camera.
The spiders’ main prey is the banded sugar ant (Camponotus consobrinus), which climbs eucalyptus trees after dusk to forage. The body length of the ants is twice that of the spiders.
A hunting spider attaches itself to the trunk of the tree with a single silk line and then lies in wait for the ants, facing downwards. When an ant comes close, the spider jumps and use its hindmost pair of legs to attach the silk line to the ant – a move that takes less than a tenth of a second. The spider doesn’t stop there, but instead somersaults over the ant and downwards.
It ends up dangling from the line below the ant and well out of its reach. The spider then grabs hold of the tree trunk and circles around the ant to thoroughly entangle it in the silk line, only moving in for the kill once it is safe.
As far as Aceves-Aparicio and his colleagues are aware, this behaviour has never been described before in any spider. The technique allows the spider to capture large and dangerous prey with little risk – the team never saw any spiders being injured.
It is also extremely successful, succeeding in 87 per cent of the attempts observed by the team. That is a much higher success rate than that of predators such as lions, wolves and cheetahs, whose attacks succeed less than half the time.
Another animal that hunts ants on tree trunks, the feather-legged assassin bug, has a success rate of just 2.5 per cent.
“They succeed a lot, beyond other predators,” says Aceves-Aparicio.
Journal reference: PNAS, DOI: https://doi.org/10.1073/pnas.2205942119
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