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GREEN Sea Turtle
(Chelonia mydas)
 General
Characteristics
The
name of the green turtle originates from the green color of the
fat located beneath its carapace (shell). The carapace is oval
shaped and has four pairs of costal scutes (non-overlapping) and
the margin is sometimes scalloped, but not serrated like the
hawksbill. Coloration of the green turtle’s carapace is variable
in adults, usually earth tones such as, pale to dark greens or
yellow, sometimes with radiating stripes. Their plastron is
yellowish in color. Their head is rounded, approximately 15 cm
(6 in.) wide and easily distinguished by having one pair
(instead of two pairs like most sea turtles) of prefrontal
scales (scales located in front of its eyes). Within the eastern
Pacific Ocean, some experts consider the East Pacific green
turtles, commonly known as black turtles, a separate species C.
agassizii; however, genetic analyses do not support such
taxonomic distinctiveness. Pacific green turtles are distinctly
darker in color (grey or black).
Size
The
green turtle is the largest of the Cheloniidae family; their
carapace typically measures 120 cm (4 ft.) in length and weighs
up to 230 Kg. (507 lbs.). They have a single claw on each
flipper. The largest green turtle ever found was 152 cm (5 ft.)
in length and weighed 395 Kg. (871 lbs.). Pacific green turtles
are smaller, typically measuring 80 cm (2 ½ ft.) as seen in the
photo on the right.
 Habitat
Green turtles are found in all temperate, sub-tropical and
tropical waters throughout the world. However, it is common for
them to stay near the coastline and around islands, living in
bays and protected shores, especially in areas with seagrass
beds. They are rarely observed in the open ocean.
Diet
The
diet of the green turtle is thought to change significantly
during its lifetime. Juveniles are carnivorous, often eating sea
worms, crustaceans and aquatic insects, as well as grasses and
algae. The green turtle is the only sea turtle that is
essentially herbivorous as an adult, showing a tendency to eat
mostly seagrass and algae. Their jaws are finely serrated,
helping them graze on vegetation. Green turtles play an
important ecological role by delivering nutrients from
nutrient-rich areas (for example, seagrass beds) to
nutrient-poor areas like nesting beaches.
Nesting
The
green turtle is thought to be one of the longest living sea
turtles, and reaching sexual maturity
at a late age, estimated between 20 and 50 years. Green turtles
are also known for their nesting site fidelity, which means the
same turtle will return to the same beach each time she is ready
to nest, often emerging within a few hundred yards of her last
nest. They nest every two years or more, laying between three
to five times per season. The green turtle lays an average of
115 eggs in each nest, where they will incubate for about 60
days. Nesting occurs throughout the east coast of the United
States and Caribbean down to the northern coasts of South
America. However, the largest nesting site in the western
Hemisphere is located in Tortuguero, Costa Rica.
The
Pacific green turtles have been spotted as far north as British
Columbia, Canada and Baja California and as far south as Chile.
Most nesting occurs in Mexico, Central America and the Galapagos
Islands.
Hatchlings
Green turtle hatchlings are generally dark brown or black in
color and easily distinguished by their white underside and
white flipper margins. The typical carapace length is 49 mm (2
in.).
Migrations
Green turtles are highly migratory, utilizing a broad range of
habitats throughout their lifetime.
One method of tracking sea turtles is through the
use of flipper tags which are placed on nesting turtles and
encoded with a distinct number. Tag returns offer information
vital for conservation efforts, but lack information regarding
the actual migration route of the turtles that satellite
tracking can offer. The longest running tagging project and one
of the largest nesting colonies of green turtles is in
Tortuguero, Costa Rica, where information collected from long
term tag returns have shown that turtles nesting in Tortuguero
disperse to feeding areas throughout the Caribbean, mainly to
the Miskito Coast of Nicaragua. This information enables
conservation efforts to be focused on specific geographic areas.
Current Status
The
World Conservation Union (IUCN) classifies the species as
Endangered (facing a very high risk of extinction in the wild in
the near future).
Threats
One
of the most detrimental human threats to green turtles is the
intentional harvesting of eggs and adults from nesting beaches
and foraging grounds.
The meat of the green turtles is also considered
to be a delicacy, thus is commercially harvested. Bycatch in
marine fisheries, habitat degradation and disease are other
detrimental threats to green turtles.
Population Trends
Trends are difficult to determine for this species due to the
wide fluctuations in year to year nesting. However, they still
nest in significant numbers in Florida and some studies have
shown stable, if not increasing, populations in areas such as
Tortuguero, Costa Rica. This may be attributed to increased
protection efforts.
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.
Sources:
Caribbean Conservation Corporation & Sea Turtle Survival League
(www.cccturtle.org)
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:
East Pacific green turtle - Wallace J. Nichols
Feeding green turtle - Caroline Rogers
Nesting green turtle - Matthew Godfrey
Hatchlings – Caribbean Conservation Corporation
Illustrations:
Tom McFarland
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