The skift is cutting through the water and as we make our way through the sludge-coloured river an enormous cerulean butterfly, the size of my hand, momentarily lands on my arm.
It flits off just as our guide, Nixon, motions to the captain to cut the engines. As we silently glide towards the banks, which are covered in a tangle of vines, he points upwards, binoculars glued to his eyes. Eventually we spot it: a grey, fluffy sloth hanging upside down in a giant Cecropia tree.
