A group of bluehead wrasse (Thalassoma bifasciatum) shoal (group together) above a reef at St. Croix, U.S. Virgin Islands. Shoaling is a common anti-predator behavior for reef fishes such as the bluehead wrasse. Many reef fish species form large, very dense shoals as juveniles. A recent study found that there is safety in numbers at small spatial scales: solitary bluehead wrasse had higher mortality rates than conspecifics in groups. The same study also found that the inverse is true for wrasse morality when measured at larger spatial scales. This photograph originally appeared on the cover of Ecology (88:12) in December of 2007.