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\u2019s no joke.<\/p>\n
\u201cThey get into a position where they can get an arm over a shrimp\u2019s back without being detected by its antennae,\u201d said Roy Caldwell of the University of California, Berkeley, who led the research.<\/p>\n
A quick tap then startles their prey into fleeing straight into the open tentacles.<\/p>\n
\u201cI\u2019ve never seen anything like it,\u201d said Caldwell,. \u201cOctopuses 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.\u201d<\/p>\n
This sophisticated hunting technique is not the species\u2019 only peculiarity. It is also perhaps uniquely, sociable for an octopus, gathering in groups of up to 40 in the wild.<\/p>\n
This might, said Caldwell, be because den sites are clustered together on occasional rocky outcrops in their estuarine habitat.<\/p>\n
The striking coloration probably aids communication. \u201cIn 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,\u201d Caldwell said.<\/p>\n