Axel Gomille's Image

Millions of monarch butterflies migrate down North America to spend the winter in the small, cold but sheltered forest site of El Rosario, high in the mountains of central Mexico.

'The sheer density is unbelievable,' says Axel. 'I had never seen anything like this before. It was breathtaking. They landed on my fingers, my cap, my camera - everywhere.' In March, as the temperature increases, the monarchs start to become more active and the migration northward begins. After warming up in the first rays of the early-morning sun, the roosting monarchs fly down to drink: they need water to make use of their tiny fat reserves. Axel's aim was to capture both the butterflies' movement and their rich colours 'lit up against the dark forest backdrop'. This required lying almost in the puddle, so that the sun lit the butterflies from the side, highlighting the ones in the air. 'When they take off, it sounds like wind.'