IT IS FOUR O'CLOCK in the morning on the Mexican prairie. My eyes hurt as I stumble back towards my truck, tripping on rocks and tussock grasses. I am exhausted - my colleagues and I have been on the road for 18 hours, beginning in the US, then enduring interminable Mexican border controls before crossing these vast, empty plains. It's -2°C, but the chill is intensified by an icy wind. Yet despite being so cold and tired, I am in high spirits - we have just released our first black-footed ferrets into the wilds of Mexico. The sight of these small, weasel-like animals bounding across the grassland and disappearing down prairie-dog holes will stay with me forever. The release on that cold day - 18 September 2001 - in the Janos region of the state ofChihuahua marked the start of an ambitious project to return the species to the wild in North America.