Through intimidation, sharks regulate the behavior of prey species, and prevent them from overgrazing vital habitats.  Some shark scientists believe that this intimidation factor may actually have more of an impact on the ecosystem than what sharks eat.  For example, scientists in Hawaii found that tiger sharks had a positive impact on the health of sea grass beds.  Turtles, which are the tiger sharks’ prey, graze on sea grass.  In the absence of tiger sharks, the turtles spent all of their time grazing on the best quality, most nutritious sea grass, and these habitats were soon destroyed.  When tiger sharks are in the area, however, turtles graze over a broader area and do not overgraze one region.