Octopus mood swings revealed in high definition

Pushing a high definition TV screen up to the side of an octopus's aquarium tank and showing them images of crabs and other octopuses, scientists have revealed these intelligent marine creatures can undergo major mood swings ranging from glum to excitable and aggressive.

Previous attempts to show moving pictures to octopuses have failed, probably because the old style cathode ray TV screens only show pictures 26 times a second, which isn't fast enough for their sophisticated eyes so the images were probably unrealistic and incomprehensible to them.

Renata Pronk and colleagues from Macquarie University, Australia decided to try octopuses on the new generation of liquid crystal high definition TV screens and with a bit of trial and error they discovered that octopuses do respond to image shown at a rate of 50 frames a second.

They were working a species that lives in Sydney harbour called, Octopus tetricus, and known as the Gloomy Octopus. The team knew the octopuses could see the HD images when they rushed up and tried to attack pictures of a crab - their favourite food.Show them film of another octopus and they dash to the back of the aquarium and try and hide.

Publishing in the Journal of Experimental Biology, the team repeated their tests over the course of several weeks and uncovered the octopuses' mood swings.

In the same day, an individual octopus reacted in a consistent way to film of a crab or another octopus. But later the same week, their behaviour was often very different. Some animals were initially quite excitable, but on another occasion were gloomy and much less enthusiastic.

The team also tested the octopuses' curiosity, showing them film of a jar they hadn't seen before. Some days they weren't bothered by it, and other days they would be curious and go take a look.

While it seems that octopus may have personalities, they aren't especially consistent over time. Get them on a bad day and an octopus can be very grumpy, but try again tomorrow and you might find a very different animal indeed.

Now that Pronk and the team have worked out how to play octopus movies they are keen to find out more about these extraordinary, intelligent animals including how they communicate with each other.