BBC The Blue Planet Disc 4: Coasts (2002)

Each year the entire population of green turtles that live off the coast of Brazil undertakes a massive 5,000-mile migration to the tiny seven-mile-wide island of Ascension, lost in the middle of the Atlantic. How they manage to navigate remains a mystery but each year 5,000 female turtles make it to the island to lay their eggs. After laying three to four clutches of eggs each every two weeks or so, they have to make the return journey to Brazil. The whole cycle takes six months and the turtles do not feed at all during this time.

Four hundred thousand Ridley's turtles co-ordinate their return to land in a massive simultaneous egg lay called an arribada. It's hard enough for turtles to drag themselves up the beach but what about fish? Every year, millions of capelin appear along the coasts of Newfoundland. They literally throw themselves out of the sea and for miles the beach is covered with writhing fish. Like the turtles, they are here to lay their eggs.

In far eastern Russia in the Sea of Okhotsk is the island of Talan. In summer, four million seabirds crowd its spectacular cliffs.

The world's largest eagle, the Stellar's sea eagle, steals kittiwakes from their nesting cliffs. As sunset approaches literally hundreds of thousands of crested auklets appear out to sea like great clouds of smoke. They return together to their cliffside nests to avoid the peregrines, ravens and sea eagles that swoop on them in mid-air.

Walruses have to come to the land each year to moult and rest from the cold, and on Round Island in the northern Pacific 40,000 of them cram on to just a mile or so of beach. When they emerge from the water they are still white but after a short time on the land they gradually turn pink! At sea they

restrict their blood flow to the centre of their bodies to keep in the heat, but when they land they dilate their vessels and allow blood to flush their skin.

Every year along the coast of Patagonia, the same very experienced group of killer whales makes an appearance - at exactly the same time as the sea lion pups are starting to swim. As the pups play in the surf a whale comes crashing out of nowhere to try and snatch them. This whale is taking a real risk and has to be very careful not to get stranded on the beach. It appears to play with its catch like a cat with a mouse. Sometimes with a powerful flick of the tail it catapults the pups over 100 metres into the air. It's hard to understand why the whales do this, but the hunting season is short and soon the pups learn to stay clear of the water. After just two weeks the killers move on.
Index Jul 18, 2011 copyleft Peter Chen