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OLIVE RIDLEY SEA TURTLE
(Lepidochelys olivacea)
 
General
Characteristics
The
name of the olive ridley originates from the olive color of the
adult’s carapace. Its head is triangular in shape, measuring up
to 13 cm (5.1 in.) wide, with two pairs of prefrontal scales.
Their carapace is circular and flat with a uniquely high and
variable number (six to nine pairs) of costal scutes, and ranges
from olive green to dark grey in color. The plastron is cream
colored and has a small and distinct pore close to the rear
margin of each of the four inframarginal scutes. Its body is
deeper than the Kemp’s Ridley (L. kempii), which is found
primarily in the Gulf of Mexico and along the eastern coast of
the USA.
Size
The
olive ridley is one of the smallest sea turtles; the length of
the carapaces is approximately 65 cm (2 ft.) and reaches up to
50 kg. (110 lbs.). Both the front and rear flippers have one, or
sometimes two, claws.
Habitat
Olive ridleys are found throughout the tropical waters of the
Pacific, Indian and southern Atlantic Oceans. In the eastern
Pacific they range from Mexico to Colombia and are sometimes
found off the southwestern coast of the United States.
Non-nesting individuals are often found in Isla de Margarita
(Venezuela) and Trinidad & Tobago; however, they rarely go
deeper into the Caribbean. They typically forage offshore in
surface waters, primarily in bays and estuaries. They may dive
to depths of 150 meters (500 ft.) to feed on bottom- dwelling
crustaceans.
Diet
Their large and powerful jaws are adapted to their diet of
mostly fish, mussels and crustaceans, particularly shrimp.
Nesting
In
addition to solitary nesting, the olive ridleys nest in great
aggregations, often called “arribadas”. During this phenomenon,
which i s often predicted by moon phases and tides, many
thousands of turtles come out to nest within a short period of
about 3 to 5 days. Although it seems to be a disastrous
experience in the sense that nesting turtles dig up the nests
laid by other turtles due to such a high density, it does have
advantages in that it decreases the predation on both nests
and hatchlings by quickly filling up their predators, as well as
increasing the chance a hatching has to make it to the ocean.
The olive ridley may only nest one, two or perhaps three times
per season, but can nest annually or every two years.
Inter-nesting periods are approximately 28 days for “arribada”
nesters and 14 days for solitary nesters. Each nest typically
has more than 100 eggs, which take approximately 55 days to
hatch. Many important mass nesting sites as well as solitary
sites are found within the American Continent, for example, one
is located along the Pacific coast of Mexico, two along the
Pacific coast of Costa Rica, and others, although smaller, along
the Nicaraguan coast. The largest nesting population is thought
to be located in the Indian Ocean, with an average of almost
400,000 females nesting per year.
Hatchlings
Hatchlings are dark grey in color and typically measure 42 mm
(1.65 in.).
Migrations
Although olive ridleys may nest annually, the species is indeed
highly migratory. Recent studies show that olive ridleys reside
in oceanic habitats of the eastern Pacific Ocean when they are
not nesting.
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
Direct harvest of adults and eggs, incidental capture in
commercial fisheries, especially shrimp trawlers, and loss of
nesting habitat are main concerns for the survival of this
species.
Population Trends
There is evidence of downward trends at various “arribada”
nesting sites, for example, at Playa Nancite, Costa Rica. The
nesting population in Surinam and adjacent areas has also shown
a decline, estimated at more than 80 percent over the last
couple of decades. However, other nesting populations along the
Pacific coast of Mexico and Costa Rica appear to be stable or
increasing. Because of the existence of large aggregated
nesting sites, the olive ridley is considered to be the most
abundant sea turtle species in the world; however, one of the
problems facing an accurate population estimate is the
difficulty and inaccuracy of counting nesting females during an
“arribada”.
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.
The
Convention allows exceptions for use of sea turtles and their
parts to satisfy economic subsistence needs, provided that such
exceptions do not undermine efforts to achieve the objective of
this Convention and the Party provides a management program
including limits on levels of intentional take.
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:
Olive ridley - Scott Handy
Olive ridleys mass nesting in Ostional, Costa
Rica – Michael Jensen
Hatchling -
©
Dr Michael Ebner
Illustrations:
Tom McFarland |
