Living to an average of about 100 to 150 years, with a heart-shaped grey-brown shell up to 3 feet long, green sea turtles weigh as much as 200 to 400 pounds. Adult green sea turtles are the only herbivorous sea turtles. When young, they are carnivorous, eating sponges, snails and crabs, but as adults they eat seaweeds, algae and seagrass. The head - which, unlike many other species of turtle, green sea turtles are unable to retract into their shell - is much smaller than other varieties, making their dark eyes appear even larger.
Male green sea turtles are born on land, but spend virtually their entire lives at sea. Hawaiian beach sightings therefore are mainly females and juveniles. History plays a huge part in the reproduction cycle - green sea turtles migrate hundreds of miles to breeding grounds to mate, and female green sea turtles then travel to the same beaches to nest as their predecessors.
