Doco 7.30pm, Seven
National Geographic’s biggest and most expensive documentary series took three years to shoot, and it shows. Great Migrations is a stunning visual triumph. This is the Australian free-to-air premiere of this series, which chronicles migrations of everything from zebra in Botswana and wildebeest in Kenya to the monarch butterfly, the sperm whale and the Christmas Island red crab. Tonight’s vision of those dinner platesized crabs marching in a clicking sea of red towards the sea is unforgettable and a little shudder-making.