A house mouse standing by a urine scent mark, visible as a wet mark on the ground just in front
of the mouse. The dark background reflects the nocturnal activity of these animals. This image relates to a paper that appeared in the Dec. 14, 2012, issue of Science, published by AAAS. The paper, by Sarah Roberts at University of Liverpool, Leahurst Campus in Neston, UK, and colleagues was titled, "Pheromonal Induction of Spatial Learning in Mice."