During autumn, large herds of migrating symets pick their way among the low hills and fill the air with their chorus of pings. When herds find water sources in desert areas, such as wide rivers, they rush in to drink. A huge cloud of dust will hang over and behind a herd, lingering in the air for miles.These herbivores are curious animals that appear to have a head at either end of their trunk, and as predators charge toward them, they begin to turn in place, rotating rapidly in a gathering cloud of dust. They stop and it is revealed why nature has equipped these animals with a head and tail of almost the exact shape and size: it is hard to tell which end of the beast is which. To a creature relying on sonar recognition, they present a confusing image. The direction of their imminent pursuit is completely conjectural. This is why they are named symets, for their protective symmetry.