Photo: Getty ImagesSome of our Strange Science stories this week include a new study on mice showing that regular exercise can help reduce the risk of Alzheimer’s disease, how experimental birth control attacks sperm like a virus and North America’s most common skunk. Exercise may stave off Alzheimer’s by regulating iron levels in the brain Experimental birth control attack on sperm like a virus Doubling the number of species of hand-standing spotted skunks Scientists built a tiny robot to mimic the mantis shrimp’s knock-out punch