Sea Turtles
Sea turtles are large turtles that inhabit warm waters of our planet's
oceans, bays and estuaries. They are similar to their terrestrial (land)
cousins, the tortoises, and to freshwater turtles, except that their legs
have been modified into flippers to aid them in swimming. Their shape has
taken on a flattened, more streamlined appearance - tapering off in the rear
to allow for less water resistance during swimming. All sea turtles except
the leatherback turtle have a hard carapace (top shell) and another hard
shell on the belly called the plastron. The carapace, as with all other
turtles incorporates their backbone, sternum and ribs. This is unlike most
other animals whose backbone and ribs are free of a shell or skin.
Sea turtles are closely related to ancient species dating back 130
million years to the Cretaceous Period. Some may be more closely related to
dinosaurs than our present day reptiles.
Like all other reptiles, sea turtles' body temperature depends upon
their surroundings which explains their migration southward as northern
waters cool off in the fall. The leatherback turtle, though, has recently
been found to be able to create some body heat, thus making them able to
withstand the chilly waters off Canada and Iceland, where they roam in the
summer. Sea Turtles are air breathers, but are capable of holding their
breath for quite some time. It is thought that they are also able to absorb
oxygen from their skin, mouth and their cloaca.
Sea turtles remain in the sea during their entire lives except for adult
females who briefly come ashore to nest in the summer months. In the eastern
US sea turtles are found mainly along the southern and Mid - Atlantic
coasts, Gulf of Mexico and in the Caribbean Sea. During the summer months
when the Gulf Stream carries warm water north as far as Canada, sea turtles,
with the exception of the hawksbill, roam as far north as Cape Cod near the
shore, while the leatherback ranges even further north.
There are five species of sea turtle in the North Atlantic Ocean -
hawksbill, loggerhead, Kemp's ridley, green and leatherback Of these, the
last four regularly inhabit Long Island's waters.
LIFE HISTORY
All sea turtles have a similar life history. Life begins as the males and
females mate in spring and early summer in the waters near the nesting
beaches. The females come ashore and deposit 80 - 200 ping pong ball-sized
eggs in a thick fluid in the 20 - 30 inch deep holes they excavate. The nest
is located in the sand on the upper part of the beach, often at the base of
the dunes or vegetation line. Females may return to the nesting beach to lay
up to 10 clutches of eggs in a season (except the Kemp's Ridley).
After the hot sand incubates the eggs for about two months the tiny
hatchlings break through the leathery shell of the egg and scramble out of
the nest to head for the water. Although this usually occurs at night, these
tiny creatures are prey to many predators such as ghost crabs, dogs, foxes,
raccoons, opossums and gulls. If they make it to the sea another set of
predators, fish and seabirds, are waiting to pick them off. It is estimated
that only a fraction of turtles that hatch actually survive this gauntlet,
and less than 1% endure to maturity. Once in the sea, the turtles will
inhabit offshore waters of the Atlantic Ocean and the Gulf of Mexico. They
remain there for several years, sometimes taking refuge in large clumps of
Sargassum weed that host a variety of small fishes and crustaceans which
presumably the turtles feed on.
After two to three years loggerheads, greens and Kemp's Ridleys move
into coastal waters in their northern range, where they spend their juvenile
life. Locally, these three species of turtles can be found in Long Island
Sound and Long Island's eastern bays where they feed on crustaceans (crabs,
shrimp, lobster, etc.), shellfish and even small fish. They arrive here
every year in late June as water temperatures rise, then migrate south to
warmer waters by late fall.
Leatherbacks lead a different lifestyle. They appear to inhabit deep
oceanic waters for most of their life feeding on jellyfish, which make up
their chief diet. Adult and sub - adult leatherback turtles are found in
Long Island's offshore waters.
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