Other common names: Olive ridley
seaturtle, pacific ridley, olive loggerhead, tortuga golfina
(Spanish) (Witherington, 2006)
The Olive
Ridley Sea Turtle, Lepidochelys
olivacea, is the smallest of sea turtles and the
most numerous. It is characterized by its olive-green coloring,
its rather large head, and its nearly round shell. It is
unique among sea turtles in that the number of lateral
scutes varies, from five to nine. Interestingly, some Olive
Ridleys are asymmetrical, with more scutes on one side
than on the other.
The Olive Ridley is a small sea turtle. Females weigh 35-45
kg (77 to 100 lbs) and have a carapace length of from 60
to 75 cm (25 to 30 in) (Witherington, 2006). They are rather
highly domed, with a flattened top to the shell, giving them
a flying saucer shape when seen from the side.
The coloring of Olive Ridley Sea Turtles is generally olive-green,
but may approach brown, gray or black. They lack the beautiful
patterns found on Hawksbill
Sea Turtles, Eretmochelys
imbricata, and Green
Sea Turtles, Chelonia
mydas. The underside, or plastron, is yellow, except
for that of juveniles, which is white. Olive Ridleys have
one claw on each front and rear flipper, two pairs of prefrontal
scales, and from five to nine lateral scutes.
While several sea turtle species have inconspicuous openings
leading from the Rathke’s glands on the lower portion of
their shells, both Olive Ridley Sea Turtles and Kemp’s
Ridley Sea Turtles, Lepidochelys
kempii, are unusual in that their four gland openings
are clearly visible. The purpose of the Rathke’s glands is
unclear, but they may secrete pheromones or a substance that
repels predators.
Olive Ridley Sea Turtles are primarily tropical, but with
some sightings as far north as Alaska and as far south as
New Zealand and Chile. Its range does not overlap that of
Kemp’s ridley, as the Olive Ridley typically does not inhabit
the Gulf of Mexico, home to the Kemp’s ridley. Olive Ridleys
in the Atlantic are found mostly on the western coast of
Africa and the Northeastearn coast of South America. In the
Pacific, they are found in large numbers off the coasts of
the Americas, but are rarely found near central Pacific islands.
Large numbers are also found in the Indian Ocean. Notable
nesting sites are located on the western coast of Central
America, northeastern South America, and the eastern coast
of India.
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| Picture of female
olive ridley sea turtles, Lepidochelys
olivacea, come and go from
nesting beach during arribada (mass
nesting) Ostional, Costa Rica, Pacific
Ocean. |
Image
#: 003581 |
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Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Testudines
Suborder: Cryptodera
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The diet of Olive Ridley Sea Turtles is varied. In their pelagic
phase, they feed on sea jellies, sea squirts, pelagic snails,
shrimp and crabs. They also eat barnacles and algae they find
on floating objects. They can dive up to 500 feet and feed
on bottom dwelling shrimp, crabs, snails, sea urchins, and
other invertebrates. They are sometimes caught on long lines
baited with squid. In coastal areas, they feed on crabs, shellfish
and fish.
Like most sea turtles, Olive Ridley Sea Turtles travel great
distances from feeding grounds to the beaches they were born
in order to nest. While some nest in isolation, the majority
wait for other Olive Ridleys to gather, and as if by signal,
they arrive on the nesting beach together in massive arribadas.
What environmental factors trigger an arribada are uncertain,
but winds, tides, moon phase, and the proximity of many other
Olive Ridleys may be contributing factors.
When an arribada occurs, thousands, sometimes hundreds of
thousands, of Olive Ridleys arrive at night on the same beach
over the course of several days. The eggs from the earliest
nests are often dug up and destroyed by later nesting turtles.
About 100 eggs are laid, and it takes about 50 to 70 days
for eggs to hatch. Females are ready to nest again in about
two weeks, but they often wait longer for the event that
signals an arribada. Olive Ridleys are thought to nest every
year.
Why arribadas have evolved is also a matter of mystery.
One hypothesis is that local beach predators quickly become
satiated on eggs they find, allowing remaining eggs to reach
maturity. However, since olive ridelys hatch en masse and
enter the ocean almost simultaneously, ocean predators gather
to take advantage of the enormous food source, thus largely
negating the previous advantage.
Olive ridley sea turtle hatchlings weigh about 17 g (1/2
oz). They hatch at night and make a fast dash to the sea
by the thousands. Some become pelagic while others make use
of coastal environments. Olive Ridleys mature faster than
most other species, reaching adulthood at between seven and
sixteen years.
While massive arribadas encourage the notion that Olive
Ridley Sea Turtles are plentiful, they are nonetheless decreasing
in number worldwide. The IUCN lists the Olive Ridley as Endangered
throughout their range. They are often caught in fishing
vessels, especially shrimp trawlers, and are frequently hooked
by longlines. They are also at risk from floating plastic
garbage, which they ingest, and from pollution which destroys
their nesting sites. Dogs, coyotes, pigs and other predators
eat their eggs, as do humans in various parts of the world.
For a diagram helpful in identifying the Olive Ridley Sea Turtle,
see: http://marinebio.org/species.asp?id=318
• Olive Ridley Sea Turtle information assembled from published
and on-line sources by Kevin
Miller on Nov. 9, 2006 for SeaPics.com.
Sources:
Perrine,
D. Sea Turtles of the World, Voyageur Press, 2003
Ripple,
J. Sea Turtles, Voyageur Press, 1996
Witherington,
B. Sea Turtles, Voyageur Press, 2006
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