The make-up industry is never going to believe this, but scientists in Spain have shown how eating poo can be used for cosmetic effects. But luckily this doesn't mean that a trip to Superdrug is about to get very unpleasant - the studies were done using a rare breed of vulture which lives in Spain. This bird is distinctive for having a bright yellow face, due to the presence of carotenoid pigments. Carotenoids are chemicals found in many fruit and vegetables, and give carrots their distinctive orange colour. But no one could work out how these vultures managed to get the carotenoids into their diet since they prefer to feast on rotting meat rather than tucking into a plateful of salad. The clue came from the Spanish folk-lore names for these birds- "churretero" or "moniguero", meaning "dung-eater". They had been seen getting down to a spot of coprophagy, chowing down on cow dung. This is extremely unusual behaviour in birds, and its purpose was a mystery until the Spanish scientists measured the levels of carotenoids in the poo. They found significantly high levels of the chemicals, particularly in areas where the cows fed on fresh, green pastures. Thus they solved the mystery of how the vultures keep their bright yellow faces, but personally I think I'll stick to the fake tan.