This video explains how predators may have varying effects under different conditions. The ecology of fear plays itself out in other intertidal ecosystems. Periwinkle snails can decimate salt marsh grasses in much the same way that crown conchs decimate oyster reefs when left unchecked. Predators are what keep periwinkles in check, and one of their main predators is the very same crown conch. Dr. Randall Hughes investigates how the conch’s fear effects vary in different tidal conditions.