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LEATHERBACK SEA TURTLE
(Dermochelys coriacea)
 General
Characteristics
The
leatherback is the only sea turtle that lacks a hard shell
(carapace). Their name is derived from the fact that their soft
shell is composed of a thin layer of tough, rubbery skin,
similar to leather which is strengthened by thousands of tiny
bony plates. The leatherback lacks scutes and scales that are
present only in the first few weeks of life. The
skin is typically black with white or pale spots. Their
streamlined, flexible carapace has seven longitudinal ridges
(keels), while the plastron varies in color and has five ridges.
Size
The
leatherback is the largest of all sea turtles - a female can
weigh roughly 500 Kg (1100 lbs.). Their carapace measures
between 130 and 175 cm (Aprox. 4-6 ft.), while their large head
represents approximately 20% of the entire carapace length. They
have powerful front flippers which lack claws. The largest
leatherback reported was a male captured more than 15 years ago
in Wales (Great Britain), weighing approximately two tons (1,000
kg / 2,200 lbs) and measuring
 3.05
meters (slightly more than 10 ft.) from the tip of its beak to
the end of the tail.
Habitat
The
leatherback is the deepest diver of all sea turtles and exhibits
the most extensive distribution. A typical dive lasts 15 minutes
and rarely reaches depths of more than 200 meters (650 ft.),
although dives deeper than 1,000 meters (3,300 ft.) have been
reported. They are found world wide, primarily in pelagic (open
ocean) waters of temperate and
tropical oceans as well as in very cold sub-artic waters.
It is common
to observe them in temperate waters of the eastern as well as
western United States of America and Canada. Leatherback turtles
exhibit great thermal tolerance; they can maintain their core
body temperature up to 18 degrees Celsius (64 ºF) above the
temperature of the surrounding water. The reasons behind this
ability to retain their body heat may be associated with various
characteristics, including thermal inertia derived from their
great body mass, the fatty sub-dermal layer which acts as an
insulator, and counter-current heat exchanges in the flippers.
Diet
 The
leatherback lacks teeth; however, deep cusps form tooth-like
projections on the upper jaw and papillae (spiny projections)
line the throat (see photo). These are two distinctive
characteristics of their specialized diet of soft-bodied
animals, mainly jellyfish. Leatherbacks are immune to Colenterate (jellyfish) toxins; such as those found in the
venomous Portuguese man-of-war. Although specific growth rates
are unknown, leatherbacks may grow quickly by eating many times
their body weight daily.
Nesting
Although an exact age to maturity does not exist, there have
been various attempts at estimating it, placing it anywhere from
9 to 14 years, with an estimated life-span of 30 years or more.
Females nest approximately every 2 to 3 years; however, recent
research has indicated they can nest annually. Nesting occurs at
night, when the turtle drags herself up the beach, usually
beyond the high-tide line. Nesting females prefer beaches with a
reduced continental shelf (deep approach), open access free of
rocks and abrasive corals, high-energy coastlines, strong
currents and high surf. On average, a female will lay 80 eggs
with yolk, about the size of billiard balls, and 30 smaller,
oddly shaped yolkless eggs in each nest. Eggs incubate for about
65 days. Similar to other species, sex determination for
hatchlings depends on the “pivotal temperature” (where the
gender ratio is 1:1), which has been estimated to be about
29.5ºC (85ºF) in Suriname and French Guyana. As with other sea
turtle species, higher incubating temperatures favor the
 production
of females. Nesting within the American Continent occurs
throughout the Caribbean, off the northern coast of South
America, the Pacific coast of Central America and the east coast
of Florida.
Hatchlings
Hatchlings are
covered with small, soft polygonal scales and predominantly
black in color with white along the borders and crests. Other
characteristics of leatherback hatchlings include their very
long front flippers, which almost reach the entire carapace
length and their lack of claws. The typical length of the
carapace is 60 mm (2.4 in.) a nd
weight of approximately 45 grams (1.6 ounces).
Migrations
Sea
turtles spend over 90% of their lives in the water (feeding,
mating and migrating). During this time, leatherbacks, similar
to all sea turtles, have the ability to migrate hundreds,
sometimes even thousands of miles from feeding ground to nesting
beach. Therefore, to fully protect sea turtles throughout their
range, more research must be carried out about their migratory
patterns and their behaviour while in the water. Current
research, such as fitting sea turtles with satellite
transmitters has provided important information regarding this
phase of their life cycle, which can then be applied for
management purposes. For example, it is now generally
recognized that the leatherbacks nesting in the Caribbean
migrate towards the east coast of the United States and Canada,
while those nesting in Mexico and Panama migrate towards
Equatorial waters, near the Galapagos Islands. Yet, there is
still much to be learned.
Current Status
The World
Conservation Union (IUCN) classifies the species as
Critically Endangered
of Extinction,
experiencing a global decline of at least 80% of its populations
over the last 10 years. Some of the most important leatherback
populations, for example, along the Pacific coast of Mexico,
have shown up to a 90% decline over the last decade.
Threats
The principle threats to the leatherback turtles have been
identified as incidental capture in marine fisheries,
unsustainable exploitation of eggs and turtles, as well as the
destruction or alteration of their nesting habitat.
Population Trends
Scientific studies and numerous data collected
from track counts on leatherback nesting beaches in the Eastern
Pacific have shown their conservation status to be extremely
critical. These trends
of large nesting colonies continue to decline in areas with
little protection. Currently, the four largest nesting colonies
on a global scale are: the southern coast of Gabon, French
Guyana and Surinam, Trinidad and Tobago, and the Caribbean Coast
of Costa Rica and Panama; the latter three of which are located
within the area of application of the Inter-American Convention
for the Protection and Conservation of Sea Turtles.
Inter-American Sea Turtle Convention
Cooperative efforts from a variety of
governmental as well as non-governmental organizations to
conserve distinct sea turtle populations inhabiting the American
Continent have existed for many years. The Inter-American
Convention for the Protection and Conservation of Sea Turtles (IAC),
which entered into force in May of 2001, provides an opportunity
for dialogue and action favoring sea turtle management. The IAC
is the only international body establishing legal instruments
and guidelines that commit the Parties to, among others, protect
and conserve populations of sea turtles and their habitat,
reduce incidental capture and foster international cooperation
for research and management of sea turtles. Currently, eleven
countries- Belize, Brazil, Costa Rica, Ecuador, United States,
Guatemala, Netherlands Antilles, Honduras, México, Peru and
Venezuela – are Signatory countries, meanwhile two more,
Nicaragua and Uruguay, have sent in the necessary instruments
for accession to the Government of Venezuela, the official
depository nation.
Due to the critical state of the leatherback,
during the past Conference of the Parties, COP2CIT, held in
November of 2004, the Contracting Parties approved
Resolution
COP2CIT-001:
“Conservation of leatherback turtles (Dermochelys coriacea)”,
urging these countries to take necessary actions to reverse the
critical situation of this species,
insisting that they act upon unsustainable harvesting of sea
turtles and their eggs, the destruction or alteration of their
habitats, and incidental capture, while strengthening
cooperative efforts with pertinent organizations in the region
and creating coordinated efforts to avoid the imminent
extinction of the leatherback.
Sources:
Caribbean Conservation Corporation & Sea Turtle Survival League
(www.cccturtle.org)
Chacón, Didiher.
INF-16-04: “Synopsis of the
Leatherback Sea Turtle (Dermochelys coriacea)”
NOAA Fisheries Office of Protected Resources (www.nmfs.noaa.gov/pr/species/turtles)
Pritchard, P.C.H.
and J.A. Mortimer. 1999. Taxonomy, External Morphology, and
Species Identification, p. 21-38.
In:
K.L. Eckert,
K.A. Bjorndal, F.A. Abreu G. and
M.A. Donnelly (Editors), Research and Management Techniques for
the Conservation of Sea
Turtles. IUCN/SSC Marine Turtle
Specialist Group Publ. No. 4. Washington, D.C.
Wider Caribbean Sea Turtle Conservation Network (www.widecast.org)
Published by:
Pro Tempore Secretariat of the Inter-American
Convention for the Protection and Conservation of Sea Turtles (IAC),
San Jose, Costa Rica, April 2005
Edited by:
Belinda Dick
English Translation:
Belinda Dick
Photo Credits:
Leatherback – Karumbé Project (Uruguay), 2003
Papillae
in
female leatherback (2 photos) - Karumbé Project (Uruguay), 2003
Leatherback clutch - Matthew Godfrey
Hatchling - Johnson 2002, www.floridaleatherbacks.com
Illustrations:
Tom McFarland
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