Fish may be as clever as primates, scientists now suspect, after new footage showed octopus and grouper fish communicating and collaborating to catch prey.
The astonishing partnership was captured for the first time by filmmakers shooting on the Great Barrier Reef for BBC Blue Planet II.
Grouper and octopus hunt the same small fish which dart in and out of the coral, and often hide in crevices which are too small for the grouper to follow.
But the larger fish has come up with an extraordinary solution. After chasing a fish into a crevice, it turns slightly paler to attract the octopus’ attention, before standing on its head and wiggling its tail to signal that a meal is hiding in the hole.
For its part, the octopus pokes its long, thin tentacles into the crevice, flushing out the prey.
Sir David Attenborough, who narrates the series said: “The fish takes fright and swims straight into the grouper’s jaws. Sometimes the octopus gets the reward, sometimes the groper does.
“These very different species have discovered that teamwork brings success.”
The footage will be screened this week in the third episode ‘Reef’ of Blue Planet II which is focussing on the creatures who live on and around coral reefs.
Scientists now think the partnership between the grouper and octopus, which involves rudimentary sign language, shows intelligence which could rival that of crows or even chimpanzees, our closest relative.
Dr Alex Vail, a Cambridge University scientist turned camerman, who led crews to the spot after witnessing the behaviour first hand said: "When I first saw it, I was blown away.
"What's fascinating is there seems to be intention behind it. The grouper has formulated a plan and is aware of what the outcome might be, and then carries it out. Which shows a similar level of intelligence as chimpanzees. And that's without anything like the same brainpower.
"We have seen grouper do similar headstand signalling and shimming to attract the attention of moray eels, but the eels often don't quite get what they are supposed to do. And the grouper sometimes has to go and nudge it in the right direction. You don't have that with the octopus. It knows what's going on and it's straight over. Which actually makes it harder to film."
Jonathan Smith, producer of ‘Reef’ said: “What we discovered is that this fish is capable of forward planning and co-operatively hunting with a completely unrelated animal, in this case an octopus.
“The grouper finds the fish and if he can’t get to it in the coral he goes off and does a display
to the octopus.
“He puts his head down, flashes white, wiggles in front of the octopus and gets its attention.
“Then they both come over to where the fish is hiding and if the octopus wants to play, it can use its tentacles to get in and actually flush the fish out.
“Once it’s out in the open the coral grouper gets the fish about half the time, and about half the time the octopus snags it.
“If we’d have tried to film that sequence a few years ago we’d have ended up filming a lot of it from slightly above. With the underwater probe camera we managed to get inside the reef and you’re looking in the reef like you’re a little fish with these octopus tentacles coming down all around you.
“You really feel like you’re experiencing this behaviour.”
Other astonishing collaborations filmed for the episode include a small shoal of bream coming together to blow away sand covering a dangerous metre long bobbit worm, which lies in wait to snatch fish and suck them under the ocean floor. The fish work together to expose the worms so that know where they are, and can to avoid their vice-like jaws.
A male and female saddleback clownfish off the coast of Borneo were also recorded joining forces to move a coconut shell close to the safety of their anemone, so the female could lay eggs.
The new episode has also recorded the dawn chorus of sea creatures as they awaken in the morning, as well as a turtle lying back to enjoy a ‘spa’ treatment from hundreds of cleaner fish.
Blue Planet II director James Honeyborne: “It's a remarkable story. Reefs are one of the most competitive areas to live in the ocean so to get ahead you've got to come up with these ingenious techniques.”