"A quick tap then startles their prey into fleeing straight into the open tentacles" – A shadowy hunter that waits silently for the perfect moment to strike

The larger Pacific striped octopus from the Eastern Pacific has mastered the irritating schoolboy prank of tapping someone on the wrong shoulder. For the victims, though, it’s no joke.

“They get into a position where they can get an arm over a shrimp’s back without being detected by its antennae,” said Roy Caldwell of the University of California, Berkeley, who led the research.

A quick tap then startles their prey into fleeing straight into the open tentacles.

• It might look like a clam, but don’t be fooled – this is no clam. It walks on two legs and tucks its home under its arms wherever it goes

“I’ve never seen anything like it,” said Caldwell,. “Octopuses typically pounce on their prey or poke around in holes until they find something. When this octopus sees a shrimp at a distance, it compresses itself and creeps up, extends an arm up and over the shrimp, touches it on the far side and either catches it or scares it into its other arms.”

• Octopuses could help us build robots that rescue people from collapsed buildings. Here's how

This sophisticated hunting technique is not the species’ only peculiarity. It is also perhaps uniquely, sociable for an octopus, gathering in groups of up to 40 in the wild.

• Giant of the Pacific: diver has close encounter with world's biggest octopus
• Squid vs octopus: what's the difference between these multiple-limbed sea creatures?

This might, said Caldwell, be because den sites are clustered together on occasional rocky outcrops in their estuarine habitat.

The striking coloration probably aids communication. “In an aquarium the octopus appears bright and high contrast, but it probably needs to be that colour to be seen from a few centimetres away in 50m of murky water,” Caldwell said.

• The very cute Dumbo octopus can swallow prey whole, reproduce at any time and is named after a Disney character – meet the elusive deep-sea animal
• This deadly female octopus plans to eat her partner after sex. But the male has a defensive trick in his tentacles
• These 15 magical photos show just how uniquely beautiful octopuses can be

Top image, taken by Dave Maass, shows a Larger Pacific Striped Octopus in an aquarium at the California Academy of Sciences. Dave Maass, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons