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An Introduction to Sea Turtles
An Overview
Sea turtles are large, air-breathing reptiles that inhabit tropical and subtropical seas throughout the
world. Their shells consist of an upper part (carapace) and a lower section (plastron). Hard scales (or
scutes) cover all but the leatherback, and the number and arrangement of these scutes can be used to
determine the species.
Sea turtles come in many different sizes, shapes and colors. The olive ridley is usually less than 100
pounds, while the leatherback typically ranges from 650 to 1,300 pounds! The upper shell, or
carapace, of each sea turtle species ranges in length, color, shape and arrangement of scales.
Sea turtles do not have teeth, but their jaws have modified "beaks" suited to their particular diet. They
do not have visible ears but have eardrums covered by skin. They hear best at low frequencies, and
their sense of smell is excellent. Their vision underwater is good, but they are nearsighted out of
water. Their streamlined bodies and large flippers make them remarkably adapted to life at sea.
However, sea turtles maintain close ties to land.
Females must come ashore to lay their eggs in the sand; therefore, all sea turtles begin their lives as
tiny hatchlings on land. Research on marine turtles has uncovered many facts about these ancient
creatures. Most of this research has been focused on nesting females and hatchlings emerging from
the nest, largely because they are the easiest to find and study.
Thousands of sea turtles around the world have been tagged to help collect information about their
growth rates, reproductive cycles and migration routes. After decades of studying sea turtles, much
has been learned. However, many mysteries still remain.
Sea Turtles and Humans
Sea turtles have long fascinated people and have figured prominently in the mythology and folklore of
many cultures. In the Miskito Cays off the eastern coast of Nicaragua, the story of a kind "Turtle
Mother," still lingers. Unfortunately, the spiritual significance of sea turtles has not saved them from
being exploited for both food and for profit. Millions of sea turtles once roamed the earth's oceans, but
now only a fraction remain.
Reproduction
Only females come ashore to nest; males rarely return to land after crawling into the sea as
hatchlings. Most females return to nest on the beach where they were born (natal beach). Nesting
seasons occur at different times around the world. In the U.S., nesting occurs from April through
October. Most females nest at least twice during each mating season; some may nest up to ten times
in a season. A female will not nest in consecutive years, typically skipping one or two years before
returning.
Growth & Development
Researchers do not yet know how long baby turtles spend in the
open sea, or exactly where they go. It is theorized that they spend their earliest, most vulnerable
years floating around the sea in giant beds of sargasso weeds, where they do little more than eat and
grow. Once turtles reach dinner-plate size, they appear at feeding grounds in nearshore waters. They
grow slowly and take between 15 and 50 years to reach reproductive maturity, depending on the
species. There is no way to determine the age of a sea turtle from its physical appearance. It is
theorized that some species can live over 100 years.
Status of the Species
The earliest known sea turtle fossils are about 150 million years old. In groups too numerous to count,
they once navigated throughout the world's oceans. But in just the past 100 years, demand for turtle
meat, eggs, skin and colorful shells has dwindled their populations. Destruction of feeding and nesting
habitats and pollution of the world's oceans are all taking a serious toll on remaining sea turtle
populations. Many breeding populations have already become extinct, and entire species are being
wiped out. There could be a time in the near future when sea turtles are just an oddity found only in
aquariums and natural history museums — unless action is taken today.
What is Extinction?
How You Can Help
There are many things each of us can do to help sea turtles survive. First, we must remember that we
share the oceans and the beaches with many other species. Second, become informed about the
things that are killing sea turtles or destroying their habitat. Elected officials and other leaders are
making decisions on issues that affect sea turtles almost every day. As an informed citizen, you have
the power to influence the outcome of these issues by making your voice heard. One way to keep
informed about important issues is to join and support groups like the Sea Turtle Conservancy, which
monitor issues and encourage their members to get involved.
Why Care about Sea Turtles
Much can be learned about the condition of the planet's environment by looking at sea turtles. They
have existed for over 100 million years, and they travel throughout the world's oceans. Suddenly,
however, they are struggling to survive -- largely because of things people are doing to the planet's
oceans and beaches. But what does this mean for the human species?
It is possible that a world in which sea turtles can not survive may soon become a world in which
humans struggle to survive. If, however, we learn from our mistakes and begin changing our behavior,
there is still time to save sea turtles from extinction. In the process, we will be saving one of the
earth's most mysterious and time-honored creatures. We might just be saving ourselves too.
Major ecological effects of sea turtle extinction
1. Sea turtles, especially green sea turtles, are one of the very few animals to eat sea grass. Like
normal lawn grass, sea grass needs to be constantly cut short to be healthy and help it grow across
the sea floor rather than just getting longer grass blades. Sea turtles and manatees act as grazing
animals that cut the grass short and help maintain the health of the sea grass beds. Over the past
decades, there has been a decline in sea grass beds. This decline may be linked to the lower numbers
of sea turtles.
Sea grass beds are important because they provide breeding and developmental grounds for many
species of fish, shellfish and crustaceans. Without sea grass beds, many marine species humans
harvest would be lost, as would the lower levels of the food chain. The reactions could result in many
more marine species being lost and eventually impacting humans. So if sea turtles go extinct, there
would be a serious decline in sea grass beds and a decline in all the other species dependant upon the
grass beds for survival. All parts of an ecosystem are important, if you lose one, the rest will
eventually follow.
2. Beaches and dune systems do not get very many nutrients during the year, so very little vegetation
grows on the dunes and no vegetation grows on the beach itself. This is because sand does not hold
nutrients very well. Sea turtles use beaches and the lower dunes to nest and lay their eggs. Sea turtles
lay around 100 eggs in a nest and lay between 3 and 7 nests during the summer nesting season.
Along a 20 mile stretch of beach on the east coast of Florida sea turtles lay over 150,000 lbs of eggs in
the sand. Not every nest will hatch, not every egg in a nest will hatch, and not all of the hatchlings in a
nest will make it out of the nest. All the unhatched nests, eggs and trapped hatchlings are very good
sources of nutrients for the dune vegetation, even the left over egg shells from hatched eggs provide
some nutrients.
Dune vegetation is able to grow and become stronger with the presence of nutrients from turtle eggs.
As the dune vegetation grows stronger and healthier, the health of the entire beach/dune ecosystem
becomes better. Stronger vegetation and root systems helps to hold the sand in the dunes and helps
protect the beach from erosion. As the number of turtles declines, fewer eggs are laid in the beaches,
providing less nutrients. If sea turtles went extinct, dune vegetation would lose a major source of
nutrients and would not be as healthy and would not be strong enough to maintain the dunes,
resulting in increased erosion. Once again, all parts of an ecosystem are important, if you lose one, the
rest will eventually follow.
Sea turtles are part of two ecosystems, the beach/dune system and the marine system. If sea turtles
went extinct, both the marine and beach/dune ecosystems would be negatively affected. And since
humans utilize the marine ecosystem as a natural resource for food and since humans utilize the
beach/dune system for a wide variety of activities, a negative impact to these ecosystems would
negatively affect humans.
What is Extinction?
A plant or animal becomes extinct when the last living individual of its species dies, causing it to
vanish from the earth forever. If there is ever a time when the last green turtle on earth dies, then
never again will this magnificent creature grace our world.
Species have been going extinct for millions of years; it is a natural part of the evolutionary process.
For example, most of the species that existed during the time of dinosaurs have perished. Many
probably went extinct because of sudden geological or climatic changes -- possibly because of a large
volcanic eruption or because of a giant meteor hitting the earth. Today, however, species are going
extinct because of abrupt changes brought about by humans. Habitat destruction, pollution and
overconsumption are causing species to decline at a rate never before seen in history. This loss of
species is eroding the diversity of life on earth, and a loss of diversity can make all life vulnerable.
General Patterns and Behavior of Sea Turtles
Sea turtles are generally solitary creatures that remain submerged for much of the time they are at
sea, which makes them extremely difficult to study. They rarely interact with one another outside of
courtship and mating. Ridleys, however, do come together in massive groups during nesting. But even
when large numbers of turtles gather on feeding grounds or during migration, there is little behavioral
exchange among individuals. Because of the difficulty in studying marine turtles in the open ocean,
there are a great many things still unknown about their behavior. Decades of research, however,
including observations at sea, have produced useful insights into daily activities and behaviors such as
courtship, mating and nesting.
Daily Activities
Sea turtles are known to feed and rest off and on during a typical day. During nesting season, research
conducted in the southeast United States helped discovered that loggerheads follow regular patterns
between the nesting beach itself and offshore reefs and other rocky structures. It is presumed that
mating and/or feeding occurs at these offshore areas. When it is not nesting season, sea turtles may
migrate hundreds or even thousands of miles. Sea turtles can sleep at the surface while in deep water
or on the bottom wedged under rocks in nearshore waters. Many divers have seen green turtles
sleeping under ledges in reefs and rocks. Hatchlings typically sleep floating on the surface, and they
usually have their front flippers folded back over the top of their backs.
Courtship & Mating
Courtship and mating for most sea turtles are believed to occur during a limited "receptive" period
prior to the female's first nesting emergence. Afterwards, only females come ashore to nest; males
almost never return to land once they leave the sand of their natal beach. During mating season,
males may court a female by nuzzling her head or by gently biting the back of her neck and rear
flippers. If the female does not flee, the male attaches himself to the back of the female's shell by
gripping her top shell with claws in his front flippers. He then folds his long tail under her shell to
copulate.
Females observed on the nesting beach after recently mating often have scratched shells and may be
bleeding from where the males' were hooked to their shells. Copulation can take place either on the
surface or under water. Sometimes several males will compete for females and may even fight each
other. Observers of sea turtle mating have reported very aggressive behavior by both the males and
females. Females may mate with several males just prior to nesting season and store the sperm for
several months. When she finally lays her eggs, they will have been fertilized by a variety of males.
This behavior may help keep genetic diversity high in the population.
Nesting, Incubation and Emergence
Very little is known about why sea turtles nest on some beaches and not on others. In Florida,
loggerheads nest by the thousands on the central east coast, while identical looking beaches to the
north see far fewer loggerheads. This nesting distribution may reflect conditions that existed centuries
ago, when temperature, beach profiles or the lack of predation made some areas preferable to sea
turtles. Today, humans are affecting the places where sea turtles nest. Beach erosion caused by
coastal armoring and navigational inlets, artificial lighting and beach renourishment are all impacting
once pristine beaches. These changes will likely have lasting effects on future nesting patterns. The
more we understand about how, where and when sea turtles nest, the better we will be able to protect
their nesting habitat.
Beach Selection
Most females return faithfully to the same beach each time they are ready to nest. Not only do they
appear on the same beach, they often emerge within a few hundred yards of where they last nested.
Nesting Behavior
Only the females nest, and it occurs most often at night. The female crawls out of the ocean, pausing
frequently as if carefully scoping out her spot. Sometimes she will crawl out of the ocean, but for
unknown reasons decide not to nest. This is a "false crawl," and it can happen naturally or be caused
by artificial lighting or the presence of people on the beach. Most females nest at least twice during the
nesting season, although individuals of some species may nest only once and others more than ten
times. Sea turtles are generally slow and awkward on land, and nesting is exhausting work.
Constructing the Nest
The female turtle crawls to a dry part of the beach and begins to fling away loose sand with her
flippers. She then constructs a "body pit" by digging with her flippers and rotating her body. After the
body pit is complete, she digs an egg cavity using her cupped rear flippers as shovels. The egg cavity
is shaped roughly like a tear drop and is usually tilted slightly.
Laying and Burying the Eggs
When the turtle has finished digging the egg chamber, she begins to lay eggs. Two or three eggs drop
out at a time, with mucus being secreted throughout egg-laying. The average size of a clutch ranges
from about 80 to 120 eggs, depending on the species. Because the eggs are flexible, they do not break
as they fall into the chamber. This flexibility also allows both the female and the nest to hold more
eggs. Nesting sea turtles appear to shed tears, but the turtle is just secreting salt that accumulates in
her body. Many people believe that while laying her eggs a sea turtles goes into a trance from which
she can not be disturbed.
This is not entirely true. A sea turtle is least likely to abandon nesting when she is laying her eggs, but
some turtles will abort the process if they are harassed or feel they are in danger. For this reason, it is
important that sea turtles are never disturbed during nesting. Once all the eggs are in the chamber,
the mother turtle uses her rear flippers to push sand over the top of the egg cavity. Gradually, she
packs the sand down over the top and then begins using her front flippers to refill the body pit and
disguise the nest. By throwing sand in all directions, it is much harder for predators to find the eggs.
After the nest is thoroughly concealed, the female crawls back to the sea to rest before nesting again
later that season or before beginning her migration back to her feeding ground. Once a female has left
her nest, she never returns to tend it.
Incubation
Incubation takes about 60 days, but since the temperature of the sand governs the speed at which the
embryos develop, the hatching period can cover a broad range. Essentially, the hotter the sand
surrounding the nest, the faster the embryos will develop. Cooler sand has a tendency to produce
more males, with warmer sand producing a higher ratio of females.
Emerging from the Nest
Unlike baby alligators, which are liberated from their nest by their mother, sea turtle hatchlings must
do it all themselves. To break open their shells, hatchlings use a temporary, sharp egg-tooth, called a
"caruncle." The caruncle is an extension of the upper jaw that falls off soon after birth. Digging out of
the nest is a group effort that can take several days. Hatchlings usually emerge from their nest at
night or during a rainstorm when temperatures are cooler. Once they decide to burst out, they erupt
from the nest cavity as a group. The little turtles orient themselves to the brightest horizon, and then
dash toward the sea.
If they don't make it to the ocean quickly, many hatchlings will die of dehydration in the sun or be
caught by predators like birds and crabs. Once in the water, they typically swim several miles off
shore, where they are caught in currents and seaweed that may carry them for years before returning
to nearshore waters. There are many obstacles for hatchlings in the open ocean. Sharks, big fish and
circling birds all eat baby turtles, and they die after accidentally eating tar balls and plastic garbage.
The obstacles are so numerous for baby turtles that only about one in 1,000 survives to adulthood.
Migration and Navigation Abilities
Migration
The ability of a sea turtle to migrate hundreds (and occasionally thousands) of miles from its feeding
ground to its nesting beach is one of the most remarkable acts in the animal kingdom. That adult
females return faithfully to nest on the very beach where they were born makes the feat even more
amazing. Research into where and how sea turtles migrate has been a focus of scientists for decades.
The information collected is vital to the development of conservation strategies for the species. We
now know that sea turtles undergo migration throughout their lives, beginning with the first frenzied
swim as a hatchling.
During its first critical 48 hours, a hatchling must travel from the beach to a place in the ocean where
it is relatively safe from predators and where it can find food. Many hatchlings in the Atlantic and
Caribbean make their way into Gulf stream currents, which are filled with floating sargassum weed.
There the young turtles find an ample food supply and few predators. After several years of floating
around the Atlantic, these young turtles are big enough to venture back into nearshore waters.
"Although all Florida loggerheads appear to spend a period of years within the North Atlantic gyre,
different turtles probably do not follow precisely the same migratory route. In the diagram at left, the
red lines indicate some possible migratory paths that different individuals may take. In addition,
whereas most turtles appear to circle the gyre only once, some individuals may make more than one
circuit, others may spend time in the Sargasso Sea, and a few have been captured in the
Mediterranean."
Sea turtles typically spend their juvenile years eating and growing in nearshore habitats. Once they
reach adulthood and sexual maturity, it is believed that they migrate to a new feeding ground. It is in
this primary feeding area where adult turtles probably remain throughout their lives, except during
breeding season. When it is their time to mate and nest, both males and females leave their feeding
grounds and migrate to the nesting beach. This periodic migration will continue throughout their lives.
Navigation
In the open ocean, sea turtles encounter strong currents; they have only modest vision, they can only
raise their heads several inches out of the water, and there are often no visible landmarks. Even with
these limitations, sea turtles regularly navigate long distances to find the same tiny stretch of nesting
beach. How they do it is one of the greatest mysteries in the animal kingdom, and finding an answer
has been the focus of generations of researchers. One promising new theory on how sea turtles
navigate suggests that they can detect both the angle and intensity of the earth's magnetic field. Using
these two characteristics, a sea turtle may be able to determine its latitude and longitude, enabling it
to navigate virtually anywhere. Early experiments seem to prove that sea turtles have the ability to
detect magnetic fields. Whether they actually use this ability to navigate is the next theory being
investigated.
Studying Migration
The migratory nature of sea turtles creates a number of challenges for those working to fully
understand and protect these creatures. In particular, to adequately protect sea turtles in all their
habitats, we must know where these habitats are, how the turtles behave while there, and routes the
turtles take to migrate back and forth. Most sea turtle research has been carried out on nesting
beaches — and for very logical reasons. These areas are easier for researchers to access, and what
occurs on the nesting beach (production of new sea turtles) is extremely important to the species'
survival. Conservation efforts are also most easily directed at nesting beaches. However, of all the
places where sea turtles travel throughout their life cycle, the least amount of time is spent on the
nesting beach. Well over 90% of a sea turtle's life is spent in the water — feeding, mating, migrating
and doing whatever else a sea turtle does when no one is watching. Consequently, the threats faced
by sea turtles in the ocean present the greatest challenges to conservationists.
To fully protect sea turtles throughout their range, more must be known about their migratory
patterns and their behavior in the water. Several methods are used by researchers to determine where
sea turtles move. One of the simplest methods involves placing a small, harmless metal tag on one of
the turtle's flippers when she comes ashore to nest. Each tag includes a coded number and a message
asking people to return the tag to a certain address if it is found. When people return a tag, they get a
small reward and are asked where the turtle was encountered. In this way, researchers gradually learn
about the many places to which turtles migrate. In the case of turtles nesting at Tortuguero, Costa
Rica, tag returns make it clear that turtles nesting there disperse to feeding areas throughout the
Caribbean. A large portion of them go to the Miskito Coast of Nicaragua. Efforts are now focused on
limiting the number of turtles killed there for meat. The use of flipper tags has provided vital
information, but it still leaves many questions unanswered.
Satellite Telemetry
Researchers have recently begun utilizing satellites to track sea turtles in the open ocean, see Sea
Turtle Migration Tracking Education Program. First, a Sony Walkman-sized transmitter is attached to
the back of an adult or juvenile sea turtle. The transmitter is glued directly to the turtle's carapace,
behind the head, where the unit's small flexible antenna can break the surface to transmit when the
turtle comes up to breathe. A passing Argos satellite receives the information and transmits it back to
researchers on earth. After 8-10 months, the transmitter quits working and eventually falls safely off
the turtle.
Using computer mapping programs, researchers can then see where the turtles migrate, what routes
they travel and how fast they generally swim. If the map one is using has enough detail, it is also
possible to determine the habitat characteristics at the turtle's location. After monitoring a number of
turtles in a specific population, researchers gradually learn where that population's major feeding
grounds are located and what threats they may be facing at sea. This information, of course, allows
conservationists to focus efforts on the most important areas.
What to do if you encounter a Sea Turtle
In Florida and other states where sea turtles nest, turtle watches are conducted by trained and
permitted individuals. The goal is to educate people about sea turtles through direct contact, without
disturbing the turtles.
Sometimes people encounter sea turtles on their own while walking on the beach at night during
nesting season. If this happens to you, here are some simple rules to follow:
* Do not walk on the beach with a flashlight or shine a light in the sea turtle's face. The light
may cause the female to abort the nesting process, or other sea turtles nearby may be
discouraged from nesting if there are lights on the beach.
* Do not take pictures using flashes. This high-intensity light can be even more disturbing than
the flashlights.
* Stay clear and out of sight of the turtle until she begins laying eggs, otherwise you may scare
her back into the sea.
* For your safety, stay away from the turtle's head. Sea turtles, especially loggerheads, have
very strong jaws and can harm you if provoked.
* Do not handle the eggs or put any foreign objects into the nest. You can introduce bacteria or
injure the eggs.
* Do not handle or ride the sea turtle. In addition to being illegal, you may injure the turtle or
cause her to leave without finishing nesting.
* Do not disturb tracks left by turtles. Researchers sometimes use the tracks to identify the
type of turtles that nested and to find and mark the nests.
* Do enjoy the experience, and remember it for the rest of your life.
Common Name: Loggerhead - named for its exceptionally large head.
Scientific Name: Caretta caretta
Description: Head is very large with heavy strong jaws. Carapace is bony without ridges and has
large, non-overlapping, rough scutes (scales) present with 5 lateral scute. Carapace is heart shaped.
Front flippers are short and thick with 2 claws, while the rear flippers can have 2 or 3 claws. Carapace
is a reddish-brown with a yellowish-brown plastron. Hatchlings have a dark-brown carapace with
flippers pale brown on margins.
Of all the sea turtles that nest in the United States, the loggerhead is the one seen most often and is
the only sea turtle species listed, in 1978, as endangered. Loggerhead populations in Honduras,
Mexico, Colombia, Israel, Turkey, Bahamas, Cuba, Greece, Japan, and Panama have been declining.
The majority of loggerhead nesting is concentrated in two main areas of the world -- at Masirah Island,
Oman, in the middle east and on the coast of the southeastern United States. The Masirah Island's
annual nesting population is about 30,000 females, while up to 25,000 loggerheads nest in the
southeast U.S. each year. The majority of nesting in the southeast U.S. takes place on Florida's
Atlantic coast between the inlet at Cape Canaveral and the Sebastian Inlet, especially within the Archie
Carr National Wildlife Refuge.
Size: Typically 2.5 to 3.5 feet in carapace length (80-110 cm).
Weight: Adult weigh between 155 and 375 pounds (70 -0 170 kg).
Diet: Primarily carnivorous and feed mostly on shellfish that live on the bottom of the ocean. They eat
horseshoe crabs, clams, mussels, and other invertebrates. Their powerful jaw muscles help them to
easily crush the shellfish.
Habitat: Prefer to feed in coastal bays and estuaries, as well as in the shallow water along the
continental shelves of the Atlantic, Pacific and Indian Oceans.
Nesting: Nest at intervals of 2 to 4 years. They lay 3 to 6 nests per season, approximately 12 to 14
days apart. Lays average of between 100 to 126 eggs in each nest. Eggs incubate for about 60 days.
Status: U.S. - Listed as Threatened (likely to become endangered, in danger of extinction, within the
foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as
Endangered (facing a very high risk of extinction in the wild in the near future) by the International
Union for Conservation of Nature and Natural Resources.
Threats to Survival: The greatest threat is loss of nesting habitat due to coastal development,
predation of nests, and human disturbances (such as coastal lighting and housing developments) that
cause disorientations during the emergence of hatchlings. Other major threats include incidental
capture in longline fishing, shrimp trawling and pollution. Incidental capture in fisheries is thought to
have played a significant role in the recent population declines observed for the loggerhead.
Population Estimate*: 44,560 nesting females.
Common Name: Green Sea Turtle - named for the green color of the fat under its shell. (In
some areas, the Pacific green turtle is also called the black sea turtle.)
Scientific Name: Chelonia mydas
Description: They are easily distinguished from other sea turtles because they have a single pair of
prefrontal scales (scales in front of its eyes), rather than two pairs as found on other sea turtles. Head
is small and blunt with a serrated jaw. Carapace is bony without ridges and has large, nonoverlapping, scutes (scales) present with only 4 lateral scutes. Body is nearly oval and is more
depressed (flattened) compared to Pacific green turtles. All flippers have 1 visible claw. The carapace
color varies from pale to very dark green and plain to very brilliant yellow, brown and green tones with
radiating stripes. The plastron varies from white, dirty white or yellowish in the Atlantic populations to
dark grey-bluish-green in the Pacific populations. Hatchlings are dark-brown or nearly black with a
white underneath and white flipper margins.
Green turtles are an endangered species around the world, but they still nest in increasing numbers on
the east coast of Florida. The green sea turtle was listed in the United States as endangered in 1978.
The largest nesting site in the Western Hemisphere is at Tortuguero, Costa Rica, where STC has been
running a research program since 1959. While the nesting population may be stable in Suriname, and
increasing in Tortuguero, there is insufficient information from other nesting sites to determine a
species trend worldwide.
For comparison, the Pacific green turtle (aka Black Sea Turtle) has a body that is strongly elevated or
vaulted and looks less round in a frontal view than other green sea turtles. The color is where you see
the biggest difference with Pacific greens having a dark grey to black carapace and the hatchlings are
a dark-brown or black with narrow white border with white underneath.
Size: Adults are 3 to 4 feet in carapace length (83 - 114 cm). The green turtle is the largest of the
Cheloniidae family. The largest green turtle ever found was 5 feet (152 cm) in length and 871 pounds
(395 kg).
Weight: Adults weigh between 240 and 420 pounds (110 - 190 kg).
Diet: Changes significantly during its life. When less than 8 to 10 inches in length eat worms, young
crustaceans, aquatic insects, grasses and algae. Once green turtles reach 8 to 10 inches in length,
they mostly eat sea grass and algae, the only sea turtle that is strictly herbivorous as an adult. Their
jaws are finely serrated which aids them in tearing vegetation.
Habitat: Mainly stay near the coastline and around islands and live in bays and protected shores,
especially in areas with seagrass beds. Rarely are they observed in the open ocean.
Nesting: Green turtles nest at intervals of about every 2 years, with wide year-to-year fluctuations in
numbers of nesting females. Nests between 3 to 5 times per season. Lays an average of 115 eggs in
each nest, with the eggs incubating for about 60 days.
Range: Found in all temperate and tropical waters throughout the world.
Status: U.S. - Listed as Endangered (in danger of extinction within the foreseeable future) under the
U.S. Federal Endangered Species Act. International - Listed as Endangered (facing a very high risk of
extinction in the wild in the near future) by the International Union for Conservation of Nature and
Natural Resources.
Threats to Survival: The greatest threat is from the commercial harvest for eggs and food. Other
green turtle parts are used for leather and small turtles are sometimes stuffed for curios. Incidental
catch in commercial shrimp trawling is an increasing source of mortality.
Population Estimate*: 88,520 nesting females.
Common Name: Leatherback - named for its unique shell which is composed of a layer of
thin, tough, rubbery skin, strengthened by thousands of tiny bone plates that makes it look "leathery."
Scientific Name: Dermochelys coriacea
Description: Head has a deeply notched upper jaw with 2 cusps. The leatherback is the only sea
turtle that lacks a hard shell. Its carapace is large, elongated and flexible with 7 distinct ridges running
the length of the animal. Composed of a layer of thin, tough, rubbery skin, strengthened by thousands
of tiny bone plates, the carapace does not have scales, except in hatchlings. All flippers are without
claws. The carapace is dark grey or black with white or pale spots, while the plastron is whitish to
black and marked by 5 ridges. Hatchlings have white blotches on carapace.
The leatherback is the champion of sea turtles: It grows the largest, dives the deepest, and travels the
farthest of all sea turtles. They were listed as endangered in the United States in 1970. Populations
have declined in Mexico, Costa Rica, Malaysia, India, Sri Lanka, Thailand, Trinidad, Tobago, and Papua
New Guniea. Leatherbacks are seriously declining at all major nesting beaches throughout the Pacific.
The decline is dramatic along the Pacific coasts of Mexico and Costa Rica and coastal Malaysia. Nesting
along the Pacific coast of Mexico declined at an annual rate of 22% over the last 12 years, and the
Malaysian population represents 1% of the levels recorded in the 1950s. In contrast, there has been a
recent increase in leatherback nesting on the central and south eastern coast of Florida.
Size: 4 to 6 feet (130 - 183 cm). The largest leatherback ever recorded was almost 10 feet (305 cm)
from the tip of its beak to the tip of its tail and weighed in at 2,019 pounds (916 kg).
Weight: 660 to 1,100 pounds (300 - 500 kg).
Diet: Leatherbacks have delicate, scissor-like jaws. Their jaws would be damaged by anything other
than a diet of soft-bodied animals, so they feed almost exclusively on jellyfish. It is remarkable that
this large, active animal can survive on a diet of jellyfish, which are composed mostly of water and
appear to be a poor source of nutrients.
Habitat: Primarily found in the open ocean, as far north as Alaska and as far south as the southern tip
of Africa, though recent satellite tracking research indicates that leatherbacks feed in areas just
offshore. Known to be active in water below 40 degrees Fahrenheit, the only reptile known to remain
active at such a low temperature.
Nesting: Nest at intervals of 2 to 3 years, though recent research has indicated they can nest every
year. Nests between 4 to 7 times per season, with an average of 10 days between nestings. Lays an
average of 80 fertilized eggs, the size of billiard balls, and 30 smaller, unfertilized eggs, in each nest.
Eggs incubate for about 65 days. Unlike other species of sea turtles, leatherback females may change
nesting beaches, though they tend to stay in the same region.
Range: Most widely distributed of all sea turtles. Found world wide with the largest north and south
range of all the sea turtle species. With its streamlined body shape and the powerful front flippers, a
leatherback can swim thousands of miles over open ocean and against fast currents.
Status: U.S. - Listed as Endangered (in danger of extinction within the foreseeable future) under the
U.S. Federal Endangered Species Act. International - Listed as Critically Endangered (facing an
extremely high risk of extinction in the wild in the immediate future) by the International Union for
Conservation of Nature and Natural Resources.
Threats to Survival: Greatest threat to leatherback sea turtles is from incidental take in commercial
fisheries and marine pollution (such as balloons and plastic bags floating in the water, which are
mistaken for jellyfish).
Population Estimate*: 35,860 nesting females.
Common Name: Hawksbill - named for its narrow head and hawk-like beak.
Scientific Name: Eretmochelys imbricate
Description: The hawksbill is one of the smaller sea turtles. Head is narrow and has 2 pairs of
prefrontal scales (scales in front of its eyes). Jaw is not serrated. Carapace is bony without ridges and
has large, over-lapping scutes (scales) present and has 4 lateral scutes. Carapace is elliptical in shape.
Flippers have 2 claws. The carapace is orange, brown or yellow and hatchlings are mostly brown with
pale blotches on scutes.
The hawksbill turtle's status in the United States has not changed since it was listed as endangered in
1970. It is a solitary nester, and thus, population trends or estimates are difficult to determine. The
decline of nesting populations is accepted by most researchers. In 1983, the only known apparently
stable populations were in Yemen, northeastern Australia, the Red Sea, and Oman. Although they are
found in U.S. waters, they rarely nest in North America. While hawksbills nest on beaches throughout
the Caribbean, they are no longer found anywhere in large numbers.
Size: Adults are 2.5 to 3 feet in carapace length (71 - 89 cm).
Weight: Adults can weigh between 101 and 154 lbs (46 - 70 kg).
Diet: The hawksbill's narrow head and jaws shaped like a beak allow it to get food from crevices in
coral reefs. They eat sponges, anemones, squid and shrimp.
Habitat: Typically found around coastal reefs, rocky areas, estuaries and lagoons.
Nesting: Nest at intervals of 2 to 4 years. Nests between 3 to 6 times per season. Lays an average
160 eggs in each nest. Eggs incubate for about 60 days.
Range: Most tropical of all sea turtles. Tropical and subtropical waters of the Atlantic, Pacific and
Indian Oceans.
Status: U.S. - Listed as Endangered (in danger of extinction within the foreseeable future) under the
U.S. Federal Endangered Species Act. International - Listed as Critically Endangered (facing an
extremely high risk of extinction in the wild in the immediate future) by the International Union for
Conservation of Nature and Natural Resources.
Threats to Survival: The greatest threat to hawksbill sea turtle is the harvesting for their prized
shell, often referred to as "tortoise shell." In some countries the shell is still used to make hair
ornaments, jewelry, and other decorative items.
Population Estimate*: 22,900 nesting females.
Common Name: Kemp's Ridley - named Kemp's after Richard Kemp, who helped discover
and study the turtle. No one is sure why it is called ridley, possibly due to having similar nesting
behavior as the olive ridley.
Scientific Name: Lepidochelys kempii
Description: Head is moderate and triangular in size. Carapace is bony without ridges and has large,
non-overlapping scutes (scales) present. Carapace has 5 lateral scutes and is very rounded. Front
flippers have 1 claw, while the rear flipper has 1 or 2 claws. Adults have a dark grey green carapace
with a white or yellowish plastron, while the hatchlings are jet black.
Kemp's ridleys are the most endangered of all sea turtles, listed in the United States as endangered
throughout its range in 1970. The only major breeding site of the Kemp's ridley is on a small strip of
beach at Rancho Nuevo, Mexico. Kemp's ridleys nest in mass synchronized nestings called arribadas
(Spanish for "arrival"). The arribada of Kemp's ridleys occurs at regular intervals between April and
June. In 1942, a Mexican architect filmed an estimated 42,000 ridleys nesting at Rancho Nuevo in one
day. During 1995, only 1,429 ridley nests were laid at Rancho Nuevo. Recent good news is that the
nesting at Rancho Nuevo seems to be increasing with over 7,100 nests recorded in 2004! The increase
can be attributed to two primary factors: full protection of nesting females and their nests in Mexico,
and the requirement to use turtle excluder devices (TEDs) in shrimp trawls both in the U.S. and
Mexican waters.
Size: Adults measure around 2 feet (58 - 66 cm) in average carapace length.
Weight: Adults weigh between 70 and 108 pounds (32 - 49 kg).
Diet: Have powerful jaws that help them to crush and grind crabs, clams, mussels, and shrimp. They
also like to eat fish, sea urchins, squid and jellyfish.
Habitat: Prefer shallow areas with sandy and muddy bottoms.
Nesting: Kemp's ridleys nest more often than other species, every 1 to 3 years on average. They also
nest in mass synchronized nestings called arribadas (Spanish for "arrival"). Only the olive ridley also
nests this way. Kemp's ridley nest 2 - 3 times each season. They lay an average of 110 eggs in each
nest and the eggs incubate for about 55 days.
Range: Adults are mostly limited to the Gulf of Mexico. Juveniles range between tropical and
temperate coastal areas of the northwest Atlantic Ocean and can be found up and down the east coast
of the United States.
Status: U.S. - Listed as Endangered (in danger of extinction within the foreseeable future) under the
U.S. Federal Endangered Species Act. International - Listed as Critically Endangered (facing an
extremely high risk of extinction in the wild in the immediate future) by the International Union for
Conservation of Nature and Natural Resources.
Threats to Survival: The greatest threat to the Kemp's ridley is from human use activities including
collection of eggs and killing adults and juveniles for meat and other products. The significant decline
in the number of Kemp's ridley nests was a result of high levels of incidental take by shrimp trawlers.
Population Estimate*: More than 2,500 nesting females.
Common Name: Olive ridley - named for its olive green colored shell
Scientific Name: Lepidochelys olivaceaf
Description: Head is quite small. Carapace is bony without ridges and has large scutes (scales)
present. Carapace has 6 or more lateral scutes and is nearly circular and smooth. Its body is deeper
than the very similar Kemp's Ridley sea turtle. Both the front and rear flippers have 1 or 2 visible
claws. There is sometimes an extra claw on the front flippers. Juveniles are charcoal grey in color,
while adults are a dark grey green. Hatchlings are black when wet with greenish sides.
The western North Atlantic (Surinam and adjacent areas) nesting population has declined more than
80 percent since 1967. Declines are also documented for Playa Nancite, Costa Rica, however other
nesting populations along the Pacific coast of Mexico and Costa Rica appear stable or increasing. In the
Indian Ocean, Gahirmatha located in the Bhitarkanika Wildlife Sanctuary, India, supports perhaps the
largest nesting population with an average of 398,000 females nesting in a given year. This population
continues to be threatened by nearshore trawl fisheries. It is very oceanic in the Eastern Pacific and
probably elsewhere too. Large arribadas of olive ridleys still occur in Pacific Costa Rica, primarily at
Nancite and Ostional and Pacific Mexico at La Escobilla, Oaxaca.
Size: Adults measure 2 to 2.5 feet (62-70 cm) in carapace length.
Weight: Adults weigh between 77 and 100 pounds (35-45 kg).
Diet: Have powerful jaws that allow for an omnivore diet of crustaceans (such as shrimp & crabs),
mollusks, tunicates, fish, crabs, and shrimp.
Habitat: Generally found in coastal bays and estuaries, but can be very oceanic over some parts of its
range. They typically forage off shore in surface waters or dive to depths of 500 feet (150 m) to feed
on bottom dwelling crustaceans.
Nesting: Nest every year in arribadas. Nests 2 times each season. An average clutch size is over 110
eggs which require a 52 to 58 day incubation period.
Range: The olive ridley inhabits tropical and subtropical waters of the Pacific, Indian and Atlantic
Oceans.
Status: U.S. - Listed as Threatened (likely to become endangered, in danger of extinction, within the
foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as
Endangered (facing a very high risk of extinction in the wild in the near future) by the International
Union for Conservation of Nature and Natural Resources.
Threats to Survival: Direct harvest of adults and eggs, incidental capture in commercial fisheries and
loss of nesting habitat are the main threats to this species.
Population Estimate*: 800,000 nesting females.
Common Name: Australian flatback - named because its shell is very flat.
Scientific Name: Natator depressus
Description: Head has a single pair of prefrontal scales (scales in front of its eyes). Carapace is bony
without ridges and has large, non-overlapping, scutes (scales) present with only 4 lateral scutes.
Carapace is oval or round and body is very flat. Flippers have 1 claw. Edge of carapace is folded and
covered by thin, non-overlapping waxy scutes. Carapace is olive-grey with pale brown/yellow tones on
margins and the flippers creamy white. The scutes of the hatchlings form a unique dark-grey reticulate
pattern, and the center of each scute is olive colored.
Australian flatbacks are medium size turtles that inhabit coastal coral reef and grassy shallows and is
only found in the northern coastal area of Australia and the Gulf of Papua, New Guinea. The shell is
very smooth and waxy, and can be easily damaged.
Size: Adults measure up to 3.25 feet in carapace length (99 cm).
Weight: Adults weigh an average of 198 pounds (90 kg).
Diet: Apparently eats sea cucumbers, jellyfish, mollusks, prawns, bryozoans, other invertebrates and
seaweed.
Habitat: Prefer turbid inshore waters, bays, coastal coral reef and grassy shallows.
Nesting: Nests 4 times per season. Lays an average of 50 eggs at time, but these are comparatively
quite large. The eggs incubate for about 55 days. When the hatchlings emerge, they are larger than
most species.
Range: Very limited. It is found only in the waters around Australia and Papua New Guinea in the
Pacific.
Status: Australia - Listed as Vulnerable under the Australian Environment Protection & Biodiversity
Conservation Act. International - Listed as Data Deficient by the International Union for Conservation
of Nature and Natural Resources. Was previously listed as vulnerable. Change in classification does not
imply species recovery, it just indicates a lack of recent research into their abundance and distribution.
Threats to Survival: Sea turtles are threatened with capture, harvesting of eggs, destruction of
nesting beaches, ocean pollution, oil spills and entanglement in fishing and shrimp nets.
Population Estimate*: 20,285 nesting females.