Most filming done in the wild – including armoured octopuses and hypnotic cuttlefish – but some crucial behaviour had to be captured in lab conditions

Footage of captive wildlife inserted into the BBC’s Blue Planet 2 series remains “totally true to nature”, according to the makers of the flagship show that reveals new insights into life in the oceans.

An octopus that armours itself with shells and rocks, fish that use sign language and tools and dazzling cuttlefish that appear to hypnotise their prey are among the new spectacles uncovered by the series, which starts later this week.

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But, while the vast majority of the filming was done in the wild, some crucial behaviour could only be captured on film in controlled or laboratory conditions.

The BBC faced controversy in 2011 when a Frozen Planet programme, also narrated by Sir David Attenborough, combined wild polar bear footage with film of cubs in an ice den taken in a Dutch zoo, a conjunction that only emerged after the show had been broadcast.

“We wouldn’t do that now,” said Attenborough. “Because we are being very, very meticulous to be correct and not in anyway misleading.” Blue Planet 2 includes closeup lab footage of corals bleaching, as this could only be filmed with lights and specialised cameras. “To say that we are distorting natural history would be absurd,” said Attenborough.

Facebook Twitter Pinterest A giant trevally patrols the shallows of a lagoon in the Indian Ocean, waiting for fledgling birds to leap at as they fly overhead. Photograph: Screen Grab/BBC

“We make films that are totally true to nature and we’re honest and open about the techniques we use to do that,” said James Honeyborne, the executive producer of Blue Planet 2. “If you’re filming something that’s microscopic, you have to put added light on it – that’s just the the simple laws of physics.”

The Blue Planet team also worked with scientists to accurately recreate a rock pool and the burrow of a zebra mantis shrimp to enable closeup filming. The fearsome-looking fangtooth, which has the largest teeth relative to its body size for any fish, was filmed in a special chamber aboard a ship that had retrieved samples from the deep ocean.

The source of the footage is not highlighted during the programme. “You can’t just break the spell,” said Honeyborne. “But it’s very important we have a transparent relationship with our audience and that the small proportion of them that do want to know how these things are filmed can find out. We want to tell all aspects of the oceans and we will use all the film craft techniques to do that.”

Facebook Twitter Pinterest An orange-dotted tuskfish holds a clam in its jaws on the Great Barrier Reef, Australia. Photograph: Alex Vail/BBC

The making of Blue Planet 2, which involved 6,000 hours of underwater filming, required new technology to be developed. This included an ultra-low-light camera which captured the night-time ballet of mobula rays and bioluminescent plankton in the Sea of Cortez, California.

Other behaviour seen or filmed for the first time in the series is the armoured octopus discovered near Cape Town in South Africa. “It lives in the kelp and is a very camouflaged animal, living by its wits in a very shark-rich environment, where it would be a tasty morsel,” said Honeyborne. “A naturalist [Craig Foster] who lives there said I’ve seen this extraordinary behaviour when this octopus feels threatened: it picks up stones and shells on the seabed and wraps them around itself, like a protective coat.”

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On Australia’s Great Barrier Reef, a tuskfish was revealed using a specific coral nub to crack open clams, while elsewhere grouper fish were seen using a kind of sign language – the “headstand signal” – to reach across the vertebrate-invertebrate divide and encourage octopuses to help it hunt.

The cuttlefish footage was shot off Borneo, said Mark Brownlow, the series producer. “To get ahead in this crowded undersea [coral] city you have to come up with some ingenious ways,” he said. “The amazing thing about cuttlefish is that they have control of their of their skin pattern. In order to catch a crab, these cuttlefish send ripples of colour patterns down its body and, we can’t say for sure whether it’s hypnosis, but it certainly appears to mesmerise the crab to the degree that it momentarily stops, allowing the cuttlefish to make the kill. It is utterly surreal.”

Another film first showed fledgling sooty tern chicks being seized in mid-air by giant trevally fish, which erupt from the waters of a remote Indian ocean atoll. “When we first heard of it we just didn’t believe it – it’s fisherman’s tale that proved true,” said Honeyborne.

Facebook Twitter Pinterest A walrus mother and her calf rest on an iceberg in Svalbard in the Arctic. Photograph: Rachel Butler/BBC

The new series also focuses on the damage being done to wildlife in the oceans by human activity, including plastic pollution in the sea. “We filmed a young mother pilot whale carrying her dead baby, which the scientists there believe was due to toxic shock – plastics are the route by which the contaminants get into the milk,” said Honeyborne. In the Arctic, a walrus mother and her pup are seen struggling to find a patch of sea ice on which to rest – the north pole has lost about 40% of its ice since 1979.

“We are not out there to campaign,” said Brownlow. “We are just showing it as it is and it is quite shocking at times. We couldn’t ignore it – it just wouldn’t be a truthful portrayal of the world’s oceans.”

Attenborough said: “We would like to think the natural world is better understood and better respected as a consequence of what we do. You can’t respect it unless you understand it.”

Blue Planet 2 begins in the UK at 8pm on 29 October on BBC1.

This article was amended on 24 October 2017. An earlier version referred to the naturalist “Craig Forster”. The surname has now been corrected to “Foster”.