Egg cannibalism is a striking example of how stickleback behavior may depart from Tinbergen's simple description of male-female cooperation. Other recent studies call into question Tinbergen's description of the zigzag dance as a "species-specific" behavior pattern. When behavioral ecologists studied five genetically distinct populations of three-spined sticklebacks, they discovered important differences in the courtship ritual. In two populations, females rather than males initiated courtship, and the zigzag component was either missing or very inconspicuous. In both of these populations, groups of up to 300 females and immature males attacked the nests and cannibali the young. Presumably, a history of cannibalism by females in these two populations has favored males who do not advertise their nest sites with conspicuous courtship displays.