Sea Turtles in Puerto
Olive Ridley Turtle (Lepidochelys
By Griffin Page
Naturalist ~ Eco-guide
The Olive Ridley turtle (Lepidochelys Olivacea)
is one among the 8 different species of marine turtles that
exist in the world. All 8 species are in danger of extinction
and 7 of them come to nest on Mexican beaches. Two species
are actually endemic to Mexico, which means they are only
found here and nowhere else in the world: the Kemp's Ridley
(Lepidochely kempii), found in the Gulf of Mexico, and the
Black Turtle (Chelonia agassizi), whose nesting area is in
the state of Michoacán. Marine turtles are also some
of the oldest creatures that ever existed on this planet,
some 200 million years of evolution. They have managed to
survive that long and are now in danger of becoming extinct;
the reason: Human's over exploitation of natural resources.
Of all the species, the Olive Ridley is one
of the smallest in size; small in comparison to the 7 other
species of marine turtles, but not small by any of our standards
as an adult turtle averages between 26 inches (66 cms) and
36 inches (91 cms) in length and has an average body weight
close to a 100 pounds (45 kgs).
Turtle fossils dating back to 150 to 200
million years have been discovered. In those days, turtles
were much larger than the ones we have today. As can be seen
in this picture of the Archelon, the biggest of these ancestral
marine turtles, some measured up to 13 feet (4 mts.) long
and had a wingspan of 16 feet (5 mts.).
The major difference between marine turtles
and tortoises is that tortoises are land turtles, they have
toed feet, a nail protruding out of each toe and are able
to retract their heads into their carapace for protection.
Marine turtles on the other hand, have flippers with few nails
(usually 2 per flipper) and cannot insert their heads in their
carapace. However, marine turtles are better adapted to their
environment than land tortoises.
Since marine turtles are cold blooded (ectothermic),
they are unable to control their body temperature , and so,
are found in sub tropical or temperate ocean waters of around
The Olive Ridley is similar to the Kemp's
Ridley, but has a deeper body and slightly upturned edges
to its carapace. Its width is about 90 % of its length and
an adult weighs around 100 lbs (45 kgs). As in other turtle
species, males have larger and more strongly curved claws,
as well as a longer tail. This particular species is a slow
growing one; they attain sexual maturity between 8 and 12
years of age, their full adult size around 15 years of age
and it is believed, can live up to 100 years. Although they
are born with one tooth, which they use to break the shell
in order to come out of the egg, they lose it rapidly and
hence, have no teeth. Their beaks are well adapted to suit
their specific feeding needs.
Adults are usually olive-grey above and creamy
or whitish, with pale grey margins underneath. Newborn hatchlings
are almost completely black when wet and medium to dark grey
Migration and Nesting
These turtles travel thousands of miles or
kilometers between feeding and nesting grounds. Once they
reach sexual maturity, between 8 and 12 years of age, the
females return to the same beach where they were born in order
to lay their own eggs. It is believed that they actually mark
the specific location in their memory when they make their
way to the ocean from their original birth nest as newborn
babies. This is why turtle camps always release baby turtles
some distance from the water's edge and let them tread their
way into their new home.
there is a 8 year period between their birth until they reach
sexual maturity, called the lost years, where very few turtles
are ever seen. They make it to the ocean from their nests
and then just disappear for approximately 8 years. It is believed
that since the babies aren't yet strong enough to use the
ocean currents to get from the breeding to the feeding grounds,
that, in fact, the currents actually carry them far from known
concentration areas. Because these same currents also carry
a multitude of organisms that figure on the turtle's diet,
it is suspected that they can feed relatively easily.
The Olive Ridley turtles, in Mexico, are
distributed along the Pacific coast, including the Sea of
The most important breeding grounds for the Olive Ridley are:
Western central coast of Mexico - 200,000
nests per year; West coast of Costa Rica - 200,000 nests;
Nicaragua - 20,000 nests; Guatemala - 3000 nests; Honduras
- 3000 nests; Panama - 1000 nests; Surinam - 2000 nests; French
Guiana - 500 nests; Angola (Ambris), Skeleton Coast, northern
part of Mamibia - 500 nests; Mozambique - 500 nests; and India
- 300,000 ( biggest nesting aggregation still present today).
Other seasonal, but non-reproductive concentrations, occur
in feeding areas, like the eastern part of Venezuela or the
area between Columbia and Ecuador
This turtle usually migrates along the continental
shelves and feeds in shallow waters. They are carnivorous
and have quite a large variety of food items on their diet.
The well documented data collected from analysis of stomach
contents in Mexico show 9 species of gastropods, 26 species
of neogastropods, 17 species of pelecypods as well as scaphopods,
crustaceans, molluscs, amphipods, isopods, stomatopods, vertebrates
and unidentified algae. In simple terms, they eat fish, crabs,
shrimp, squid, jellyfish, fish eggs, sea grass and a minute
quantity of algae just to name a few.
These turtles attain sexual maturity between
8 and 12 years of age. The mating occurs principally near
the surface of the ocean, close to the nesting beaches or
along the migratory routes and is not often observed. If disturbed,
the coupling pair may dive down. After the coupling is over,
the partners will usually swim separately.
in other species, the male will hold the carapace of the female
with the claws of his four flippers. The mating may last for
a few minutes to several hours and occurs before and during
the nesting season. It is possible that a female may mate
with several males.
The reproduction season here, in Bay of Banderas,
begins in June and ends around December, with a higher percentage
of nestlings from July to September. A very interesting fact
is that the sex of the hatchling isn't determined in advance
by a gene but rather by the temperature during the incubation
period. For the Olive Ridley turtle, incubation temperatures
around 30° Celsius will produce about half males and half
females. Temperatures above 30° Celsius will produce more
females and the opposite occurs at lower temperatures. However,
at temperatures below 28° and over 32° Celsius, a
decrease in survival rate may occur.
Once the female is ready to lay her eggs,
she will wait for a quiet time when disturbance is at a minimum.
As mentioned before, turtles are cold blooded and cannot regulate
their body temperature. Because of this, they often choose
night time to lay their eggs. Night also offers these turtles
better protection from predation and rainy nights seem to
be as good a time as any. Let it be known that only female
turtles ever return to land and do so only to dig their nest
and lay their eggs. Once males have entered the sea, they
never return to land.
process of digging a nest and laying eggs is a difficult one
for turtles. Apart from being in a completely foreign environment,
having to drag close to 100 lbs (45kgs) of weight over the
sand for a certain distance, the turtle's vision is poor outside
water. She then has to dig, with her rear flippers, a hole
of approximately 1 1/2 feet deep (46 cms) and lay an average
of 100 eggs. She then has to cover her nest and try to camouflage
it. She will do so by shoving sand with her flippers while
rotating, creating a pattern much bigger than the original
hole and by swinging from side to side, slapping her body
on the sand to compact it. If a female is disturbed while
digging the nest, she will stop and return to the ocean. However,
if the laying of the eggs has begun, she will not stop. During
that time, she appears to be in a kind of trance. Well, we
know what it's like for humans to give birth, so you can just
imagine what laying between 50 to 130 eggs can be like. That
is why is of the utmost importance to leave them alone, in
peace, and let them carry on with their difficult task.
The reproductive cycle is usually annual,
but in some cases, turtles may reproduce and nest every 2
or 3 years. It appears that those turtles who travel further
during migrations reproduce less often than those residing
near the nesting sites which may do so almost every year.
During the nesting period, one particular turtle may reproduce
2 to 4 times and so, lay her eggs 2 to 4 times also. The average
is 2 nests per reproduction period and the quantity of eggs
is higher on the first nestlings and reduces on the subsequent
ones. For example, a turtle laying 3 times may produce 130
eggs the first time, 90 eggs the second and 60 eggs the third
time. Of course these numbers are just an example and they
also vary according to weather, depredation, disturbances
and level of health of that specific turtle.
egg size is that of a ping pong ball, perfectly round and
is rather soft, unlike a chicken egg, which allows the female
to drop them without cracking them. The incubation period
varies relatively from region to region. Here, in Banderas
Bay, the incubation period is around 40 to 50 days. Other
places in the world have shown incubation periods varying
between 45 and 65 days and is strongly correlated with temperatures
and humidity. In dry, colder weather, it lasts longer than
in areas with temperatures around 30° Celsius and a 14%
humidity level. Other parameters that influence the length
of the incubation period are: sand grain size, organic matter
content, clutch size, date of oviposition, and possibly, the
proximity to other nests. A shorter incubation period reduces
the possibilities for predation and the detrimental effects
of bad weather. In 2002 for example, most, if not all the
turtle nests in Bay of Banderas and its environs were destroyed
by hurricane Kenna.
There are only 2 species of marine turtles
that occasionally come in huge numbers to nest on a same beach.
Those are the Olive Ridley and the Kemp's Ridley turtles.
Mass arrivals or "Arribazones" usually occur every
quarter moon (14 to 28 days) and may be repeated two to seven
or eight times each season.
the beginning of summer, turtles approach special spots on
the shore and during the next quarter moon, thousands of females
arrive along a stretch of several kilometers (always less
than 10 km). This is thought to be an anti predatory technique
and may explain the generation, within short periods of time,
of locally restricted populations of hundreds or thousands
of females and hence, their success as a species. During mass
arrivals, the Olive Ridley turtle shows a cyclic response
to temperature, so usually, there are no turtles on the beach
at noon. In the afternoon, when the sands becomes fresh, the
turtles come onto the beach, increasing their number up to
a maximum around midnight, and then start leaving the beach
until the next morning. Nesting may extend for two or three
nights, and usually, is repeated every last quarter moon until
the end of autumn.
However, this technique is not always the
best approach, especially when the chosen beach is of restricted
length as in the case of Nancite and Ostional in Costa Rica.
In such cases, the turtles may excavate another turtle's nest
in an attempt to lay her own eggs. There may be a high mortality
rate in eggs, embryos and hatchlings because the time span
between each quarter moon is shorter than the incubation period.
This may also happen on longer beaches where the incubation
period is longer than 50 days.
the success of the hatchling of the egg laid in subsequent
arrivals is low on small beaches (less than 10 %), it is postulated
that the colony is supported by inter-arrival solitary nestlings
that lay clutches with higher survival rates. On longer beaches,
as in Mexico and India, the survival rate of eggs is usually
over 30%, which means that several million hatchlings enter
the sea annually. Hence, in the same species, quite different
results are obtained with the same strategy.
One of the most important nesting beaches
in Mexico is that of Playa Escobilla, in Oaxaca, and is counted
among the most important nesting beaches in the world along
with Nancite (Costa Rica) and the Bay of Bengala (Orissa,
India). For example, in 1968, it is estimated that between
the 7th and the 10th of august, over 80,000 turtles came to
nest on Escobilla. Of course, due to predation, these numbers
The Olive Ridley turtles, as with many other
species of marine turtles, encounter numerous threats through
out their lives. The predation begins as early as the incubation
period. First, the eggs can be infected by fungi and bacteria.
There is also a larvae from a fly, that, normally is supposed
to attack only dead or sick eggs, but may sometimes propagate
to healthy ones. Also during the egg stage, the predator list
may include animals such as dogs, jaguars, foxes, pigs, ants
and crabs. During the early stages of life, until they reach
adulthood, their predators are, amongst others, coyotes, foxes,
dogs, raccoons and coatis, crabs, ants, birds (such as magnificent
frigatebirds and pelicans) and fish. Sharks and killer whales
are their main natural predators when they reach adulthood,
if they make it to that stage at all.
Here's a basic list of human impacts on
marine turtles worldwide:
~ Pesticides, heavy metals and PCBs have
been detected in turtles and eggs. The effects have not yet
~ Oil spills puts turtles at risk. It affects their respiration,
skin, blood chemistry and salt gland functions.
~ Garbage can be detrimental to their survival as well. Plastic
bags, styrofoam pieces, tar balls, balloons and raw plastic
pellets can be mistaken for food and ingested by turtles thus,
interfering in their metabolism and gut function even at low
levels of ingestion and may cause absorption of toxic byproducts.
~ Where recreational boating and ship traffic occurs, direct
collisions and boat propellers cause mortal injuries.
~ Uncontrolled beach development, reduction of nesting beach
size by construction of walls and lighting on beaches.
is estimated that only 1% of all hatchlings survive to become
adults. The main reason why these wonderful creatures are
on the brink of disappearing forever is......humans! Due to
over exploitation of the turtles themselves for their meat,
eggs, skin and carapace, millions of turtles were slaughtered
every year and still are in some areas. Another even more
serious problem is the unwanted capture of turtles by commercial
longliners and trawler nets. Fortunately, some countries have
adopted TED nets (turtle excluder device) and have made them
mandatory for commercial fisheries. This type of net has a
trap door that opens when a turtle pushes into it, hence releasing
it and allowing it to surface to breathe. Millions of turtles
drowned annually in the other types of nets. Now, they are
pushing for a larger TED in order to allow the escape of bigger
sized turtles. As for longliners, a 3 year study, done by
the National Marine Fisheries Service in the USA, has demonstrated
that by a simple change in fishing equipment from "J"
hooks to a type called a "circle" hook, they could
significantly reduce the unwanted capture of turtles. Let's
hope that countries all over the world adopt these measures
in order to stop the rapid decline of these marvelous ocean
creatures and thus avoid their complete extinction.
Many countries are participating in marine
conservation projects such as turtle camps. Some are bigger
and include research while others concentrate on protecting
eggs in secure nurseries and releasing them after they hatch.
In México, there are approximately 500 turtle camps
nation wide, of which around 340 are big ones. The larger
camps, those who luckily have a little more funding than others,
may include specific data collection on the species found
in their area and most will also tag adult females while they
nest and hatchlings before they are released, and give basic
medical assistance to those who may be slightly injured. This
supplemental work has great advantages when it comes to marine
turtle conservation. The tagging, for example, allows us to
count more precisely the number of females nesting on one
particular beach and the number of hatchlings that survive
and make it back to their nesting grounds years later. In
other words, it allows us to determine much more precisely
the number of actual turtles in one area, thus giving us important
information as to the rate of decline or success of any particular
species, thus, also allowing us to make the proper adjustments
in order to increase the effect of our efforts in protection
and restoration of one species.
Education is a big part of marine turtle
conservation. It is important to dispel those myths that are
causing it's rapid decline. Turtle eggs are not an aphrodisiac;
studies have determined that as a fact. More so is that a
turtle egg's contents of bad cholesterol (LDL) is much higher
than that of a chicken egg, and we all know that even a chicken
egg can be bad for your health due to it's high content of
"bad" cholesterol. Turtle egg poaching has no reason
to exist in our world.....let us tell it like it is.
you can help
Should you encounter a female making it's
way on the beach to lay it's eggs, here's what to do:
~ Stay away from her, at least 10 feet (3.3
meters) and never place yourself in front of it, always stay
~ Be quiet and don't move around, instead, sit quietly and
enjoy this wonderful gift life has offered you. Don't forget
to get out of the way when it tries to go back to the sea.
~ Don't let people form a circle around her. That can be very
stressful to the turtle. Laying her eggs is hard enough for
~ If it happens to be nighttime, do not shine any light on
it, that may cause her to stop digging and return to the sea,
hence, not permitting her to lay her eggs.
~ Call the proper authorities for that area (local biologists
or a local turtle camp is preferable) so that they may come
and recover the eggs before poachers do their nasty work.
~ Should you encounter a hatching nest, DO NOT TOUCH the baby
turtles. Any bacteria, repellent, or food debris can be detrimental
to the hatchling's survival. Wash your hands carefully before
attempting to help a turtle stuck in debris or having difficulty
making it to the ocean. Remember to let it mark it's location,
do not put them directly in the water unless it's really necessary.
~ Some organizations collect funds that are distributed to
local camps. Don't be afraid to give, your children's future
will only be the better for it.
They say that our future lies in the hands
of our children. That is very true. On your next vacation,
bring your children to a turtle camp, teach them or let a
knowledgeable person tell them about these marvelous creatures
of the ocean. Participate in a baby turtle release program
and get the experience of a lifetime. There is little more
touching than holding a baby turtle in your hand, giving it
a name, a kiss, wishing it luck on it's tough journey ahead
and watching it make its way to its home; the sea!