S2, E5: The summer melt of Arctic ice provides opportunities for millions of animals, including narwhal, beluga whales, families of Arctic foxes and vast colonies of seabirds. But for polar bears it's the toughest time of year. The melting ice makes it harder for them to hunt and threatens their survival. In the river shallows hundreds of Beluga whales gather to rub themselves on smooth pebbles in one of the most bizarre summer spectacles. While Guillemot chicks take their first flights from precipitous sea cliff nests to the sea 300 metres below.