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Learning About

Sea Turtles

Photo by Ben Hicks

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 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.

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 March through October. Most females nest at least twice during each mating season; some may nest up to ten times in a season. Females typically don’t nest in consecutive years, often 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 30 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.

Migration and Navigation Abilities

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.

Status of the Species

In North America, leatherback, hawksbill and Kemp’s Ridley sea turtles are classified as Endangered under the Endangered Species Act, while the loggerhead, olive ridley, and green sea turtles are listed as Threatened. Internationally, hawksbill and Kemp’s ridley sea turtles are 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 (IUCN), while greens are listed as Endangered (facing a very high risk of extinction in the wild in the near future), and leatherbacks, loggerheads, and olive ridleys are listed as Vulnerable (facing a high risk of extinction in the wild in the immediate future).

Sea Turtles

Where We Are Found

Map of sea turtles
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About Sea Turtles

Species

Loggerhead

Loggerhead turtles, known for their large heads and strong jaws for crushing shellfish, are common in the U.S., especially along Florida’s East Coast, where they nest in large numbers.
Species

Green

Green sea turtles, the second largest species, are herbivores with green fat from a diet of seagrass and algae. Their biggest threat is egg and meat harvests.
Species

Leatherback

Leatherback turtles, the largest sea turtles, have a unique leathery shell made of tough skin. They inhabit all oceans except the Arctic and Antarctic.
Species

Hawksbill

Hawksbill turtles thrive in tropical coral reefs and are known for their stunning “tortoiseshell” pattern, making them targets for illegal harvest.
Species

Kemp’s Ridley

Kemp’s Ridley turtles are the smallest and most endangered sea turtles, primarily found along the Gulf, nesting in synchronized “arribadas.”
Species

Olive Ridley

Olive Ridley turtles, known for their olive green shells, are the most abundant sea turtles, found in tropical and subtropical waters globally.
Species

Flatback

Flatback sea turtles, with their distinctive flat shells, are found only in Australia and Papua New Guinea, nesting in remote areas.
Threats

Boat Strikes

Boat strikes are widely acknowledged as a significant threat to sea turtles and other marine animals.
Threats

Trawl Fisheries

Thousands of sea turtles are killed each year by commercial fishing, often drowning in nets or caught on hooks, highlighting the urgent need for global bycatch reduction efforts.
Threats

Climate Change

Climate change threatens sea turtles by eroding nesting beaches and skewing hatchling sex ratios. Warmer oceans harm coral reefs, vital for their survival.
Threats

Oil Spills

Oil spills threaten marine turtles by contaminating nesting beaches, damaging health, and reducing food sources, impacting all life stages.
Threats

Marine Pollution

Pollution harms sea turtles and their food. Toxins accumulate in the food chain, with runoff causing diseases like fibropapillomas.
Threats

Nest Predation

Sea turtles have natural predators like raccoons. The number of predators in an area can increase and dogs can dig up nests due to human development near nesting sites.
Threats

Beach Activities

Human activity on nesting beaches disrupts sea turtles, reducing nesting success and increasing false crawls, while beach driving harms hatchlings.
Threats

Beach Erosion

Current regulatory policies must change if there is any hope of saving natural beaches. These changes cannot take place without the public’s help.
Threats

Coastal Armoring

Urbanization has heavily impacted sea turtle nesting beaches. Seawalls block access to optimal nesting sites, increasing false crawls.
Threats

Artificial Lighting

Nesting turtles now face competition from tourists and coastal development, with lights disorienting hatchlings and harming survival.
Habitats

Beach and Dunes

A beach and dune ecosystem is a dynamic coastal habitat characterized by constantly shifting sands shaped by marine and terrestrial processes.
Habitats

Barrier Islands

Barrier islands form from sandbars, supporting rare species and protecting the mainland from storms. Constantly reshaped by wind and waves, they risk destruction in major storms.
Habitats

Coral Reefs

Coral reefs, rich in biodiversity, support vital fisheries and protect coasts from storms. However, they face threats from boating, diving, and pollution.
Habitats

Seagrass Beds

Seagrasses, distinct from algae, thrive in shallow coastal waters and support marine life like sea turtles. They face decline from pollution and boat damage.
Habitats

Nearshore Hardbottom

Nearshore hardbottom reefs, found in shallow waters, support 530+ species and protect beaches. Beach renourishment buries these habitats, affecting marine life and sea turtles.
Habitats

Pelagic

The pelagic oceanic zone is open water beyond the continental shelf, home to nekton and plankton, vital for marine life like tuna and sharks.
Habitats

Lagoons and Estuaries

Lagoons and estuaries mix salt and freshwater, vital for ecosystems. Lagoons provide feeding grounds for juvenile sea turtles but face pollution threats.
Habitats

Mangroves

Mangroves filter pollution, stabilize shorelines, and provide diverse habitats for many species. They support commercial fisheries but are vulnerable to development and pollution.
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FAQs

Still Have Questions?

We have more answers.

Learn more about sea turtles, their lifecycle and how humans are impacting their survival.

How are sea turtles able to return to the same beach to nest?
There are several theories as to how they locate this area, but none have yet been proven. The most common hypotheses are:

• 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 indicate that sea turtles have the ability to detect magnetic fields that can be used to identify locations and used as a compass.

• It is widely believed that hatchlings imprint the unique qualities of their natal beach while still in the nest and/or during their first trip from the nest to the sea. Beach characteristics used may include smell, low-frequency sound, magnetic fields, the characteristics of seasonal offshore currents and celestial cues.
How does a sea turtle nest?
The nesting process consists of several stages. The female turtle emerges from the sea at night and ascends the beach, searching for a suitable nesting site (somewhere dark and quiet). Once at the chosen nesting site, she begins to dig a body pit by using all four flippers. She removes the dry surface sand beneath her, which will later be used to cover the egg chamber.

Once she has created a body pit, she begins to dig an egg chamber using her rear flippers, alternating between the right and left flipper to scoop out the damp sand. When she can reach no deeper, she pauses and begins contractions, her rear flippers rising off the sand. Soon she begins laying eggs. Following each contraction, the female turtle will drop between one and four eggs in quick succession. The eggs will almost fill the chamber.

Once her clutch is complete, she closes the nest using her rear flippers in a similar way to digging her egg chamber, just in reverse. She places sand on top of the chamber, until the eggs are completely covered. She gently pats the damp sand on top of her eggs, using the underside of her shell (plastron). The camouflaging process now begins. Slowly moving forward, she throws dry, surface sand behind her. This is an effort to conceal the location of her eggs from predators. She may move forward while she is doing this. When she is done, she heads down the beach and returns to sea.
How many eggs do sea turtles lay?
The number of eggs in a nest, called a clutch, varies by species. In addition, sea turtles may lay more than one clutch during a nesting season. On average, sea turtles lay about 80 to 120 eggs in a nest, and average between 2 to 8 nests a season. The smallest clutches are laid by flatback turtles, approximately 50 eggs per clutch. The largest clutches are laid by hawksbills, which may lay over 200 eggs in a nest.
What do sea turtle eggs look like?
They are the size and shape of ping-pong balls with a soft shell. Some sea turtles lay small unfertilized eggs, which only contain albumin (egg white). The leatherback turtle lays some of these unfertilized eggs in every clutch, but the other species of sea turtle rarely lay unfertilized eggs.
What determines the sex of a sea turtle?
The temperature of the nest determines a hatchling’s gender. This is called Temperature-Dependent Sex Determination (TSD). Warmer temperatures produce mostly females, and cooler temperatures produce a majority of males. There is a pivotal temperature that produces an equal ratio of males and females. The temperature determining sex ratio differs between species and nest locations.
Do mother turtles attend to their nests?
No. Once a nest has been completed, the female never returns to it. The eggs incubate in the warm sand and hatchlings are left to fend for themselves and find their way to the ocean upon emerging from the nest.
Why do hatchlings emerge together?
Because hatchlings are small and the egg chambers are deep, it is almost impossible for a single hatchling to escape from the chamber alone. As hatchlings break free from their shell inside the egg chamber, they stimulate other hatchlings to emerge from their eggs too. Once most hatchlings have emerged from their shells, they climb on top of the discarded eggshells to propel themselves to the top of the chamber. The hatchlings near the top of the egg chamber scratch down sand from above and around them. They emerge either en masse or in small groups. Emerging together increases the chance of survival as many hatchlings can overwhelm would-be predators. A single hatchling would be an easy target.
Why do some researchers say there are seven species of sea turtles and some say there are eight species?
The difference in number is based on whether or not the black sea turtle is a separate species from the green sea turtle. The debate centers on the genetic difference between the green sea turtle and the black sea turtle. Most sea turtle researchers believe that the black sea turtle should be called the Pacific green turtle because it is a sub-species of the green sea turtle since it has almost identical genetic traits. Some sea turtle researchers believe that the physical characteristics and other behavioral difference indicate that it should be classified as its own species.
How do hatchlings locate the ocean?
Once hatchlings emerge from a nest they orient themselves away from the darkest horizon (the dunes on a naturally dark beach), towards the brightest horizon (the ocean on a naturally dark beach), and then dash in that direction. On beaches where there are lights from house, hotels, condominiums, or street lights, hatchlings can become disorientated and head away from the ocean.
What do sea turtles eat and do they have teeth?
Each species feeds on a diet specific to that species. For example, loggerheads feed mainly on hard-shelled organisms such as lobsters, scallops and crabs. Green turtles prefer sea grasses, while leatherbacks feed primarily on jellyfish. Hawksbills have a hawk-like beak that is used to cut through tough coral, anemones and sea sponges. Although green sea turtles’ jaws are serrated, all sea turtles’ jaws lack teeth. The leatherback’s jaw has 2 prominent ‘cusps’ on the upper jaw and one on the lower jaw, distinguishing it from the other turtles.
How deep can sea turtles dive?
Leatherbacks can dive to a depth of more than 1,000 meters (3,000 feet) possibly in search of their prey, jellyfish. The hard-shelled species dive at shallower depths. The leatherback is adapted to deep dives because of its unique body. Unlike other sea turtles, the leatherback lacks a rigid carapace, allowing it to compress during deep dives.
How long can a sea turtle hold its breath? And why do they drown?
As sea turtles are air breathing reptiles, they need to surface to breathe. Sea turtles can hold their breath for several hours, depending upon the level of activity. A resting or sleeping turtle can remain underwater for 4-7 hours. However, a stressed turtle, entangled in fishing gear for instance, quickly uses up oxygen stored within its body and may drown within minutes.
How big was the largest sea turtle ever recorded?
The largest species of sea turtle was the Archelon, which measured 7 meters (about 21 feet) in length and lived during the time of the dinosaurs. Today, the largest living species is the leatherback turtle. Atlantic leatherbacks are slightly larger than the Pacific population. Leatherbacks measure, on average, 2 meters (6 feet) in carapace (shell) length. The largest leatherback ever recorded was a male found stranded on the Welsh coast in 1987. He measured almost 3 meters (9 feet) from tip to tail and weighed 970 kg (2,138 lbs).
How are sea turtles tracked in the ocean and how long can they be tracked for?
Researchers track sea turtles through using satellite telemetry. A small transmitter is attached to the turtle’s carapace. The transmitter emits signals of information to an orbiting satellite when the turtle surfaces to breathe or bask. The information in the signals is sent to receiving stations on Earth, and is then sent to the researcher’s computer as a dataset. This data provides information on the turtle’s location, number of dives during the last day, length of the most recent dive, water temperature, etc. Data, received over a period of time, allows for tracking a turtles movement patterns and swimming speed.

Satellite transmitters are most often attached to females that come ashore to nest. Tracking has provided important information on migration routes between breeding and foraging (feeding) habitats. The time length of tracking depends upon how long the device remains on the turtle and on battery life. Tracking usually continues for 6-10 months, although cases have been reported exceeding 2 years. After about two years, the transmitters fall safely off the turtles.
What are the methods used to tag sea turtles?
Flipper tags are made of metal or plastic and are clipped onto the turtles’ flipper(s). These tags are clearly visible, each containing a unique serial number and the address of the organization applying the tags. There also are tags called Passive Integrated Transponder tags or “PIT tags.” These are microchips that are injected into the turtles shoulder muscle, the area of the flipper closest to the shell. Each PIT tag also has a unique digital serial number and requires the use of PIT scanning equipment to display the tag number. While PIT tags are more secure than flipper tags, their higher cost and the need for specialized equipment limits many researchers from using them.
Why are sea turtles tagged?
Sea turtles are tagged for several reasons. Flipper and PIT tags are used to identify individual turtles to help researchers learn things like nesting site fidelity, the number of nests laid during a nesting season, the number of years between nesting seasons, and growth rates. In addition, these tags can be used to identify where a captured or stranded turtle was originally tagged, which can be used to establish possible migration pathways. While flipper and PIT tags can provide starting and ending points for migration, satellite tags are able to provide research and conservationists with the actual routes that sea turtles take between different habitats.
Do sea turtles ever lay eggs underwater?
For the eggs to survive and have a chance of hatching, sea turtles must lay their eggs on sandy beaches. As they are developing, the embryos breathe air through a membrane in the eggs, and so they cannot survive if they are continuously covered with water. If disturbed, sea turtles will sometimes not nest (called a “false crawl.)” They will return to sea and usually try to nest again elsewhere later that night or within a couple days. Once a clutch of eggs is ready to be deposited, the female must deposit them to allow development of another clutch of eggs. While it is very unusual, turtles disturbed during different nesting attempts may release their eggs in the sea if they can’t carry them any longer. Captive turtles have been known to drop eggs into the water.
Which is the most common sea turtle? Which is the most endangered sea turtle?
The most common species of sea turtle is the Olive Ridley, with an estimated 800,000 nesting females. The most endangered is the Kemp’s Ridley, with an estimated 2,500 nesting females (though nesting numbers have increased over the past 10 years).
Why are sea turtles endangered?
Sea turtles once navigated throughout the world’s oceans in huge numbers. But in the past 100 years, human demand for turtle meat, eggs, skin and colorful shells have reduced 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 some surviving species are being threatened to extinction. Sadly, only an estimated one in 1 to 1,000 will survive to adulthood. The natural obstacles faced by young and adult sea turtles are staggering, but it is the increasing problems caused by humans that are threatening their future survival.
Why should humans protect sea turtles?
There are two 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. Sea turtles and manatees act as grazing animals that cut the grass short and help maintain the health of the sea grass beds. Sea grass beds are important because they provide breeding and developmental grounds for many species of fish, shellfish and crustaceans. Over the past decades, there has been a decline in sea grass beds. This decline may be linked to fewer numbers of sea turtles grazing. Without sea grass habitats, many of marine species would be lost. All parts of an ecosystem are important. If you lose one, the rest will eventually follow.

2. Beaches and dune systems do not retain nutrients well because of the sand, so very little vegetation grows on the dunes and no vegetation grows on the beach itself. Sea turtles use beaches and the lower dunes to nest and lay their eggs. Sea turtles deposit an average of about 100 eggs in each nest and lay between 3 and 7 nests during the 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. The unhatched nests, eggs and trapped hatchlings are good sources of nutrients for the dune vegetation, even the left over egg shells from hatched eggs provide some nutrients. As a result, 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 coastal ecosystem becomes better. Stronger vegetation and root systems helps to hold the sand in the dunes and helps protect the beach from erosion. If sea turtles become extinct, dune vegetation would lose a major source of nutrients and would de-stabilize the ecosystem, resulting in increased coastal erosion and reduced habitat for wildlife. 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 coastal system and the marine system. If sea turtles became extinct, both the marine and coastal ecosystems would be negatively affected. And because humans utilize the marine ecosystem as a natural resource for food and use the coastal system for a variety of activities, a negative impact to these ecosystems would negatively affect humans.
How are sea turtles scientifically classified?
KINGDOM – Animalia

PHYLUM – Chordata

CLASS – Reptilia
Class Reptilia includes snakes, lizards, crocodiles, and turtles. Reptiles are ectothermic (cold-blooded) and are vertebrates (have a spine). All reptiles have scaly skin, breathe air with lungs, and have a three-chambered heart. Most reptiles lay eggs.

ORDER – Testudines
Order Testudines includes all turtles and tortoises. It is divided into three suborders. Pleurodira includes side-necked turtles, Cryptodira includes all other living species of turtles and tortoises, and Amphichelydia includes all extinct species.

SUBORDER – Cryptodira
Suborder Cryptodira includes freshwater turtles, snapping turtles, tortoises, soft-shelled turtles, and sea turtles.

FAMILY – Cheloniidae or Dermochelyidae
Sea turtles fall into one of two families. Family Cheloniidae includes sea turtles which have shells covered with scutes (horny plates). Family Dermochelyidae includes only one modern species of sea turtle, the leatherback turtle. Rather than a shell covered with scutes, leatherbacks have leathery skin.

GENUS and SPECIES
Most scientists currently recognize seven living species of sea turtles grouped into six genera.
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