The eggs are round, covered with a parchment-like skin, and about as big as golf balls. The number of eggs laid ranges from 85 to 500. Green turtles are primarily vegetarian as adults. Leatherbacks feed almost exclusively on jellyfish. This may account for its relatively common occurrence in cold northern waters where jellyfish are seasonally abundant.
Marine turtles migrate considerable distances between their nesting and feeding grounds.
Leatherbacks have been recorded 3,000 miles from their nesting grounds. The mechanisms of sea turtle navigation have been intensely investigated, but the cues or sensory systems involved are still unknown. Both green turtles and leatherbacks probably reach Alaska by way of the warm Japan Current and North Pacific Current which reach Alaska's Alexander archipelago, arc northwestward across the Gulf of Alaska, and then flow southwestward along the Aleutian chain. The opportunities for turtle watching in Alaska obviously are not as great as elsewhere, but a sighting can be very exciting, considering the rarity of such occurrences. Documenting turtle movements in Alaska waters, in addition to offering recreation, adds to the scientific knowledge of these animals in northern waters.