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Sea TurtlesLeatherback Sea Turtle
Leatherback Sea Turtle
Common Name: Leatherback Sea Turtle
Scientific Name: Dermochelys coriacea
Description
The leatherback is the largest
turtle and the largest living reptile in the world. Mature
males and females can be as long as six and a half feet (2
m) and weigh almost 2000 lbs. (900 kg). The leatherback
is the only sea turtle that lacks a hard, bony shell. A leatherback's
carapace is approximately 1.5 inches (4 cm) thick and consists
of leathery, oil saturated connective tissue overlaying loosely
interlocking dermal bones. The carapace has seven longitudinal
ridges and tapers to a blunt point. Adult leatherbacks
are primarily black with a pinkish white mottled ventral surface
and pale white and pink spotting on the top of the head. The
front flippers lack claws and scales and are proportionally
longer than in other sea turtles; back flippers
are paddle-shaped. The ridged carapace and large flippers
are characteristics that make the leatherback uniquely equipped
for long distance foraging migrations.
Female leatherbacks lay clutches of approximately
100 eggs on sandy, tropical beaches. Females nest several
times during a nesting season, typically at 8-12 day intervals.
After 60-65 days, leatherback hatchlings with white striping
along the ridges of their backs and on the margins of the
flippers emerge from the nest. Leatherback
hatchlings are approximately 50-77 cm (2-3 inches) in length,
with fore flippers as long as their bodies, and weigh approximately
40-50 grams (1.4-1.8 ounces).
Leatherbacks lack the crushing chewing plates
characteristic of sea turtles that feed on
hard-bodied prey (Pritchard 1971). Instead, they have pointed
tooth-like cusps and sharp edged jaws that are perfectly adapted
for a diet of soft-bodied pelagic (open ocean) prey, such
as jellyfish and salps.
A leatherback's mouth and throat also have
backward-pointing spines that help retain such gelatinous
prey.
Diet
Jellyfish are the main staple
of its diet, but it is also known to feed on sea urchins,
squid, crustaceans, tunicates, fish, blue-green algae,
and floating seaweed.
Habitat
Leatherbacks are commonly
known as pelagic animals, but also forage
in coastal waters. In fact, leatherbacks are the most migratory
and wide ranging of sea turtle species. Thermoregulatory adaptations
such as a counter-current heat exchange system, high oil content,
and large body size allow them to maintain a core body temperature
higher than that of the surrounding water, thereby allowing
them to tolerate colder water temperatures. Nesting female
leatherbacks tagged in French Guiana have
been found along the east coast of North America as far north
as Newfoundland. Atlantic Canada supports one of the largest
seasonal foraging populations of leatherbacks in the Atlantic.
Leatherbacks tagged with satellite transmitters
at sea off Nova Scotia were tracked to waters adjacent to
nesting beaches along the northeast coast of South American,
the Antilles, Panama and Costa Rica (James et al., 2005).
Leatherbacks mate in the waters adjacent to nesting beaches and along migratory corridors. After nesting, female leatherbacks migrate from tropical waters to more temperate latitudes, which support high densities of jellyfish prey in the summer.
Critical Habitat
U.S. Virgin Islands – A strip of land 0.2 miles wide (from mean high tide inland) at Sandy Point Beach on the western end of the island of St. Croix beginning at the southwest cape to the south and running 1.2 miles northwest and then northeast along the western and northern shoreline, and from the southwest cape 0.7 miles east along the southern shoreline.
Distribution
Leatherback turtle nesting
grounds are located around the world, with the largest remaining
nesting assemblages found on the coasts of northern South
America and west Africa. The U.S. Caribbean, primarily Puerto
Rico and the U.S. Virgin Islands, and southeast Florida support
minor nesting colonies, but represent the most significant
nesting activity within the United States. Adult leatherbacks
are capable of tolerating a wide range of water temperatures,
and have been sighted along the entire continental coast of
the United States as far north as the Gulf of Maine and south
to Puerto Rico, the U.S. Virgin Islands, and into the Gulf
of Mexico.
The distribution and developmental habitats
of juvenile leatherbacks are poorly understood. In an analysis
of available sightings (Eckert 2002), researchers found that
leatherback turtles smaller than 100 cm carapace
length were only sighted in waters 26°C or warmer, while adults
were found in waters as cold as 0 to 15°C off Newfoundland
(Goff and Lean 1988).
Reproduction and Development
In the United States, nesting occurs from about March to July. Female leatherbacks nest an average of 5 to 7 times within a nesting season, with an observed maximum of 11 nests. The average internesting interval is about 9 to 10 days. The nests are constructed at night in clutches of about 70 to 80 yolked eggs. The white spherical eggs are approximately 2 inches in diameter. Typically incubation takes from 55 to 75 days, and emergence of the hatchlings occurs at night. Most leatherbacks remigrate to their nesting beaches at 2 to 3-year intervals. Leatherbacks are believed to reach sexual maturity in 6 to 10 years.
Population Trends
The Pacific Ocean leatherback
population is generally smaller in size than that in the Atlantic
Ocean. Because adult female leatherbacks frequently nest on
different beaches, nesting population estimates and trends
are especially difficult to monitor. In the Pacific, the World
Conservation Union (IUCN) notes that most leatherback
nesting populations have declined more than 80%. In other
areas of the leatherback's range, observed declines in nesting
populations are not as severe, and some population trends
are increasing or stable. In the Atlantic, available information
indicates that the largest leatherback nesting population
occurs in French Guyana, but the trends are unclear. Some
Caribbean nesting populations appear to be increasing, but
these populations are very small when compared to those that
nested in the Pacific less than 10 years ago. Nesting trends
on U.S. beaches have been increasing in recent years.
Threats
Leatherback turtles face
threats on both nesting beaches and in the marine
environment. The greatest causes of decline and the
continuing primary threats to leatherbacks
worldwide are long-term harvest and incidental capture in
fishing gear. Harvest of eggs and adults occurs on nesting
beaches while juveniles and adults are harvested on feeding
grounds. Incidental capture primarily occurs in gillnets,
but also in trawls, traps and pots, longlines, and dredges.
Together these threats are serious ongoing sources of mortality
that adversely affect the species' recovery. For more information,
please visit our threats
to marine turtles page.
Conservation Efforts
Because leatherbacks are
highly pelagic
animals and make long migrations, they come into
contact with people of many nations. Therefore, conservation
efforts for leatherback populations in one country may be
jeopardized by activities in another. Protecting leatherback
turtles on U.S. nesting beaches and in U.S. waters alone,
therefore, is not sufficient to ensure the continued existence
of the species.
Leatherback turtles are
protected by various international treaties and agreements
as well as national laws. Convention on International
Trade in Endangered Species of Wild Flora and Fauna (CITES),
which means that international trade of this species is prohibited.
Convention on Migratory Species (CMS This
link is an external site.) and are protected under the following
auspices of CMS: the Memorandum of Understanding on the Conservation
and Management of Marine Turtles and their Habitats of the
Indian Ocean and South-East Asia (IOSEA)
and the Memorandum of Understanding Concerning Conservation
Measures for Marine Turtles of the Atlantic Coast of Africa.
Leatherbacks are protected under Annex II of the Specially
Protected Areas and Wildlife (SPAW This link is an external
site.) Protocol of the Cartagena Convention. The U.S. is a
party of the Inter-American Convention for the Protection
and Conservation of Sea Turtles (IAC This link is an external
site.), which is the only international treaty dedicated exclusively
to marine
turtles.
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