Sea turtles are large, air-breathing reptiles
that inhabit tropical and subtropical seas throughout the world.
Their shells consist of an upper part (carapace) and a lower
section (plastron). Hard scales (or scutes) cover all but the
leatherback, and the number and arrangement of these scutes can
be used to determine the species.
Sea turtles come in many different sizes, shapes and colors. The
olive ridley is usually less than 100 pounds, while the
leatherback ranges from 650 to 1,300 pounds! The upper shell of
each sea turtle species ranges in length, color, shape and
arrangement of scales
Sea turtles, are well adapted to life in the marine environment
.
Most scientists recognize two families of sea
turtles
1. Family Cheloniidae are sea turtles with shells covered
with scutes (horny plates).
2. Family Dermochelyidae are scuteless turtles with only
one modern species, the leatherback turtle. Leatherbacks are
covered with leathery skin. They are the only marine turtle
whose backbone is not attached to the inside of the shell.
Green turtle ,
Chelonia mydas , Endangered/Threatened
Green turtles are an endangered species around the world, but
they still nest in increasing numbers on the east coast of
Florida . The green sea turtle was listed in the United States
as endangered in 1978. The largest nesting site in the Western
Hemisphere is at Tortuguero , Costa Rica , where CCC has been
running a research program since 1959. While the nesting
population may be stable in Surinam , and increasing in
Tortuguero, there is insufficient information from other nesting
sites to determine a species trend worldwide.
Hawksbill turtle
, Eretmochelys imbricata , Endangered
The hawksbill turtle's status in the United States has not
changed since it was listed as endangered in 1970. It is a
solitary nester, and thus, population trends or estimates are
difficult to determine. The decline of nesting populations is
accepted by most researchers. In 1983, the only known apparently
stable populations were in Yemen , northeastern Australia , the
Red Sea , and Oman . Although they are found in U.S. waters,
they rarely nest in North America . While hawksbills nest on
beaches throughout the Caribbean , they are no longer found
anywhere in large numbers.
Kemp's ridley turtle
, Lepidochelys kempii , Endangered
Kemp's ridleys are the most endangered of all sea turtles,
listed in the United States as endangered throughout its range
in 1970. The only major breeding site of the Kemp's ridley is on
a small strip of beach at Rancho Nuevo, Mexico . Kemp's ridleys
nest in mass synchronized nestings called arribadas .
Leatherback turtle
, Dermochelys coriacea , Endangered
The leatherback is the champion of sea turtles: It grows the
largest; dives the deepest; and travels the farthest of all sea
turtles. They were listed as endangered in the United States in
1970. Populations have declined in Mexico , Costa Rica ,
Malaysia , India , Sri Lanka , Thailand , Trinidad , Tobago ,
and Papua New Guniea. Leatherbacks are seriously declining at
all major nesting beaches throughout the Pacific. The decline is
dramatic along the Pacific coasts of Mexico and Costa Rica and
coastal Malaysia . Nesting along the Pacific coast of Mexico
declined at an annual rate of 22% over the last 12 years, and
the Malaysian population represents 1% of the levels recorded in
the 1950s. In contrast, there has been a recent increase in
leatherback nesting on the central and south eastern coast of
Florida .
Loggerhead turtle
, Caretta caretta , Threatened
Of all the sea turtles that nest in the United States , the
loggerhead is the one seen most often and is the only sea turtle
species listed, in 1978, as endangered. Loggerhead populations
in Honduras , Mexico , Colombia , Israel , Turkey , Bahamas ,
Cuba , Greece , Japan , and Panama have been declining. The
majority of loggerhead nesting is concentrated in two main areas
of the world -- at Masirah Island , Oman , in the middle east
and on the coast of the southeastern United States .
Olive ridley turtle
, Lepidochelys olivacea , Endangered/Threatened
The western North Atlantic ( Surinam and adjacent areas) nesting
population has declined more than 80 percent since 1967.
Declines are also documented for Playa Nancite, Costa Rica ,
however other nesting populations along the Pacific coast of
Mexico and Costa Rica appear stable or increasing. In the Indian
Ocean , Gahirmatha located in the Bhitarkanika Wildlife
Sanctuary, India , supports perhaps the largest population of
females nesting in a given year.
The flatback turtle,
found only in the tropical waters of Northern Australia, is
listed as vulnerable.
Australian flatbacks are medium size turtles that inhabits
coastal coral reef and grassy shallows and is only found in the
northern coastal area of Australia and the Gulf of Papua , New
Guinea . The shell is very smooth and waxy, and can be easily
damaged.
Major ecological effects of sea turtle
extinction
1.Sea turtles, especially
green sea turtles, are one of the very few animals to eat sea
grass. Like normal lawn grass, sea grass needs to be constantly
cut short to be healthy and help it grow across the sea floor
rather than just getting longer grass blades. Sea turtles and
manatees act as grazing animals that cut the grass short and
help maintain the health of the sea grass beds. Over the past
decades, there has been a decline in sea grass beds. This
decline may be linked to the lower numbers of sea turtles.
Sea grass beds are important because they provide breeding and
developmental grounds for many species of fish, shellfish and
crustaceans. Without sea grass beds, many marine species humans
harvest would be lost, as would the lower levels of the food
chain. The reactions could result in many more marine species
being lost and eventually impacting humans. So if sea turtles go
extinct, there would be a serious decline in sea grass beds and
a decline in all the other species dependant upon the grass beds
for survival. All parts of an ecosystem are important, if you
lose one, the rest will eventually follow.
2. Beaches and dune systems do not get very
many nutrients during the year, so very little vegetation grows
on the dunes and no vegetation grows on the beach itself. This
is because sand does not hold nutrients very well. Sea turtles
use beaches and the lower dunes to nest and lay their eggs. Sea
turtles lay around 100 eggs in a nest and lay between 3 and 7
nests during the summer nesting season. Along a 20 mile stretch
of beach on the east coast of Florida sea turtles lay over
150,000 lbs of eggs in the sand. Not every nest will hatch, not
every egg in a nest will hatch, and not all of the hatchlings in
a nest will make it out of the nest. All the unhatched nests,
eggs and trapped hatchlings are very good sources of nutrients
for the dune vegetation, even the left over egg shells from
hatched eggs provide some nutrients.
Threats to Sea
Turtles
1. Natural Threats - Predators such as raccoons, crabs and ants
raid eggs and hatchlings still in the nest. After reaching
adulthood, sea turtles are relatively immune to predation,
except for the occasional shark attack.
2. Human-Caused Threats- In many countries around the world,
people harvest sea turtle eggs for food. Most countries acts
aganist the taking of eggs, but enforcement is not severe and
the eggs can often be found for sale in local markets. In these
same areas, adult sea turtles are harvested for their meat.
Turtle products, such as jewelry made from hawksbill shells,
also create a direct threat to sea turtles.
3.Commercial Fishing - Each year, thousands of turtles are
caught in fishing nets and drown.
4. Marine Debris - Thousands of sea turtles die from eating or
becoming entangled in nondegradable debris each year, including
packing bands, balloons, pellets, bottles, vinyl films, tar
balls, and styrofoam.
5. Artificial Lighting - Artifical Lighting discourage females
from nesting and cause hatchlings to become disoriented and
wander inland, where they often die of dehydration or predation.
