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Part two of our spectacular Blue Planet II series
A thrilling ride on a sperm whale’s back, an astonishing dolphin dinner party and the mystery of the disappearing sea turtles kick off part two of our spectacular series on the BBC’s Blue Planet II
Prepare for the ride of your life in Blue Planet II, the epic sequel to the BBC’s original 2001 series which begins next Sunday. In the episode that deals with the vast expanses of open ocean covering 65 per cent of the Earth’s surface, a miniature camera has been secured to the back of a sperm whale by the team of scientists monitoring her in the seas off the Caribbean island of Dominica – and the footage is truly exhilarating.
As the sperm whale, who the team named Fingers, dives with her baby Digit we see the calf gently bumping and stroking her mother. The two of them chatter away using a pattern of clicks not unlike Morse Code, but when they reach the calf’s limit it returns to the surface while its mother plunges into the deep. A series of breaths taken before her descent, which saturate her blood with oxygen, fuel her extraordinary dive.
As the calf leaves her mother the clicks stop, replaced by a metronomic pattern of clicks from the mother delivered at a deafening 230 decibels – humans suffer hearing loss at 85dB. These echo-location clicks prove she’s closing in on her prey. Sure enough, the clicks stop completely as she powers into a shoal of squid and fills her stomach. Back on the surface the calf can finally feed too. She wil l guzzle her way through a bathful of her mother’s milk every day and it may be six years before she masters the art of hunting for herself.
Fingers and Digit are part of an all-female group of six sperm whales studied by the Dominica Sperm Whale Project led by Dr Shane Gero. Fingers’ epic dive is a stunning highlight, as is the extraordinary footage shot by divers of the whales sleeping vertically, some with the tips of their noses poking above the surface and others with their tails uppermost. But it’s the footage of the whales rubbing against each other that’s really exciting episode producer John Ruthven. ‘It’s similar behaviour to that of apes grooming relatives and shows great intelligence,’ says John. ‘Sperm whales are covered in flaking sheets of skin which are thought to prevent barnacles and parasites attaching to them. It probably gets itchy and rubbing relieves the itch. Behaviour like this reminds us how intelligent sperm whales are. They do, after all, have the biggest brains in the animal kingdom – five times larger than a human’s.’
A gathering of 300 sperm whales was witnessed off the north-west coast of Sri Lanka in the Indian Ocean by researcher Yoland Bosiger. She could hardly believe her eyes as underwater cameramen Dan Beecham and Didier Noirot got up close and very personal with the leviathans. ‘More than 20 whales swam towards them and then changed direction. Before we knew it they had completely surrounded our small boat,’ says Yoland. ‘The whales were so close I could have reached out and touched them with my hand.’
Dan adds, ‘I had whales to my left, right and underneath me. The clicks of so many whales communicating with each other was so powerful I could feel the sound reverberating through my body.’ The gathering, possibly an assembly of groups from all over the Indian Ocean, suggests Yoland and the team had gatecrashed some kind of whale party or perhaps even a family get-together, an event on a scale not seen since whaling started reducing the whale population.
Discoveries and revelations come thick and fast. The phenomenon of the boiling sea is the stuff of maritime legend but it’s rarely been witnessed and never filmed from the air – until now. Using a state-of-the-art long-distance camera from a helicopter off the coast of Costa Rica in Central America, series producer Mark Brownlow filmed the sea turning from a serene blue to a tumultuous white, giving the appearance that vast areas of ocean were boiling. What was actually happening was a feeding frenzy like no other – an extraordinary natural occurrence in which spinner dolphins and yellowfin tuna attack a massive shoal of lanternfish. ‘We built a special camera that could be towed behind a boat and allowed us to follow the tuna and dolphins, which are fast and effective at finding shoals of lanternfish,’ explains Mark. ‘We saw the dolphins crowd the fish into an increasingly tighter bait ball and then push it against the surface. The dolphins grab what they can and then the tuna weigh in. The sea appears to boil when these huge creatures weighing 100kg apiece smash into the shoal.’
But the most spectacular bait ball attacks must be those of the sailfish – a species similar to the marlin with a long, sword-like bill – which is reputed to be the world’s fastest fish. Forty or more can be involved in an attack on shoals of sardines off the Pacific coast of Mexico. They use their swords to slash at the shoal, disabling it and making it easy prey. Before they make runs at the bait they raise their great dorsal fins like a sail and change col- our. Their normally silvery or brownish sides suddenly sport bold stripes and spots in order to intimidate the prey and drive it into tighter balls.
Some projects prompted more questions than answers, such as when the team filmed a pregnant whale shark. Using a camera similar to the one attached to Fingers, her progress
was monitored as she approached Darwin Island, an extinct volcano in the Galapagos Islands, carrying 300 – yes, 300 – babies. She was one of 1,200 whale sharks that pitch up there between June and November each year, and with each weighing an average of 20 tons and the length of a small aircraft they make quite a sight.
But where do they actually go to give birth? The camera on the back of this particular whale shark came off after she disappeared into the abyss down the side of the volcano, presumably giving birth at some point beyond the range of even the most sophisticated equipment. And what about the strange roaring sound when smaller silky sharks and blacktip sharks rubbed their bodies against the whale shark’s rough skin as she made her way downwards? ‘Nobody has a clue what that is,’ says Mark. ‘Nobody had ever heard such a noise before and scientists were shocked to hear it.’
This episode does solve one longtime mystery though. Until now the early years in the life of a sea turtle have been called the lost years because nobody knew what happened to them or where they went. By chance, the programme-makers found the answer. ‘We spotted this floating log 100 miles off the coast of eastern Australia and when we dived below it we found a young hawksbill sea turtle,’ says John. ‘This is probably where it spends its socalled lost years. Scientists can trace the paths of turtles like this using
miniature satellite tags and the temperature sensors on those tags reveal that the reptiles keep warm and develop faster by staying close to the surface, sheltered by floating objects.’
The routines of albatrosses were more familiar to those who observe them, and the BBC crew focused on mates for life who have reared 20 chicks and are now looking after what may well be their final offspring. ‘It was hard not to be moved by the affection the birds showed to each other and by the determination they show to provide for their chicks,’ says Mark Brownlow. ‘An albatross may spend up to 20 days scouring thousands of miles of ocean for one meal.’
Like the sperm whales, it’s the sort of dedication that proves devoted parenting isn’t confined to humans.