A Look at the Marine World of Sea Turtles

Sea turtles

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Journey across the vast expanse of our planet’s oceans, from the vibrant coral reefs of the Pacific Ocean to the majestic expanses of the Atlantic, Indian, and Southern oceans, and you’ll encounter a mesmerizing sight; sea turtles gracefully navigating through some of the most awe-inspiring marine ecosystems.

For over 100 million years, these magnificent creatures have thrived in harmony with the seas, leaving an indelible mark on the very essence of our oceans. With seven distinct species gracing our planet, sea turtles have woven themselves intricately into the fabric of marine life, symbolizing resilience, endurance, and an innate connection to their watery realms.

Are you ready to embark on an extraordinary journey of discovery? Let’s delve into the captivating world of these ancient mariners, exploring their remarkable adaptations, extraordinary migrations, and wondrous tales of survival.

Sea Turtle Overview

The sea turtle is an air-breathing marine reptile that has been on earth for more than 100 million years.

The sea turtle is an air-breathing marine reptile that has been on earth for more than 100 million years. There are seven different species, and they can be found in oceans all over the world. The only places they are absent are the polar regions. That said, you’ll find more sea turtles in tropical waters compared to temperate areas, as the water here can sometimes be too cold for the sea turtle to swim quickly enough to catch its prey.

Different species prefer different habitats, so wherever you go in the world, you’ll see different sea turtles. For example, if you’re around the Australian coast, you might bump into the flatback sea turtle (Natator depressus).

The behavior of various sea turtle species is also different. Some will migrate over thousands of miles each year, whereas others will remain in one place, migrating around a very small area.

Sea turtles are egg-laying, cold-blooded creatures that belong to the family Cheloniidae & Dermochelyidae. However, sadly, every species of sea turtle is considered to be endangered, and only one in every one thousand hatchlings makes it to adulthood.

Unlike other turtle species, marine turtles are not able to retract their limbs inside their shells. Instead, they always remain outside. On the exterior of the shell, you may sometimes see barnacles growing, but this is nothing to worry about. In fact, turtles have a symbiotic relationship with these so-called parasites. This is a commensal relationship, which means that only the barnacle benefits as it is able to filter feed while attached to the turtle. However, the turtle comes to no harm from this, although if an individual has too many barnacles attached, this can weigh it down.

As I have mentioned, all species of sea turtles are endangered but it’s essential that we protect them as they’re an important part of the marine ecosystem. For example, the hawksbill sea turtle (Eretmochelys imbricata) eats the sponges that would otherwise take over coral reefs while the leatherback sea turtle (Dermochelys coriacea) is imperative for the control of jellyfish populations.

Green sea turtles (Chelonia mydas) feed on seagrass, and by constantly grazing, they are able to promote healthy growth. Moreover, if seagrass beds are left to get out of control, this promotes the growth of algae which can affect the quality of the water.

Since sea turtles come to shore to lay their eggs, they are also responsible for transporting nutrients from the ocean onto the land.

Life Cycle & Reproduction

Turtle life cycle

Sea turtles can live for decades, and it’s thought that they average around 50 to 60 years. These creatures don’t sexually mature for around 20 years, and once they start reproducing, may continue to do so for up to 10 years.

When it comes to mating, the female has a very short receptive period so the males need to spring into action. Eggs are laid on the shore but it is only the females that surface for this, and they choose a warm beach where they will dig a nest into which they will lay their eggs and then cover over as they head back to the water.


Sea turtle life cycle - eggs

Females will usually lay between three and six clutches of eggs in any given breeding season. In total, she could lay as many as 180 eggs in each of these clutches. However, she will only lay eggs every two to four years.

The eggs usually stay hidden in the sand for incubation for between 40 and 50 days, but this does depend on the species. However, what’s common among all species is that the gender of the sea turtle will depend on the temperature of the sand.


Sea turtle life cycle - hatchling

After 6 to 12 weeks, the eggs begin to crack, and out comes the newborn sea turtle, which is called a hatchling. They use a special tooth called a caruncle to chip their way out of the egg, and from here, they need to emerge from the nest and make their way to the water.

This is an exhausting process and only 1 in every 1000 hatchlings will make it to adulthood. Crawling across the sand during the day means exposing those little flippers to extreme heat, so the turtles will usually make the trip at night. What’s more, there are fewer predators around under the cover of darkness, which is another challenge these babies have to face.

Even once the hatchlings make it to the ocean, they still have their work cut out for them as it’s now swim or die.


Sea turtle life cycle - juvenile

What happens during the sea turtle’s juvenile years is largely unknown and this is why this period of its life is known as the lost years. While scientists would like to know more about what happens when they swim out to sea, attaching tracking devices would weigh them down too much. However, there are hopes that modern technological advances may give us a glimpse in the near future.

Sub Adult

Sea turtle life cycle - Sub Adult

As they come out of the juvenile stage and into the sub-adult stage, the sea turtles will make their way to the feeding grounds. What’s amazing is that any given individual may have to migrate up to 6200 miles (10,000 km) from their home beach to reach these breeding grounds.

That said, once they arrive, they have the leisure of spending the coming years here until they reach maturity, a process that could take as long as 20 years!


Sea turtle life cycle - adult

After decades, a sea turtle finally reaches adulthood; if it hasn’t succumbed to the many dangers of the ocean, like predators, plastic pollution, and a lack of food. At this stage of life, it’s time to reproduce, which means making the long trip back to their home beach.

Mating & Nesting

Sea turtle life cycle - mating & nesting

During mating season, female sea turtles will mate with several different males, and the males will try to hook up with as many females as possible to pass on their genes.

Once the female has bred, she will head back to her home beach, where she will make her way ashore and start digging nests. In these nests, she may lay up to 180 eggs per clutch, and she could dig as many as six nests per season.

When she’s finished laying, she will cover the eggs with sand to protect them and head back to the ocean, leaving her young to fend for themselves once they hatch.


Sea turtle anatomy

Carapace – The carapace is the upper part of the sea turtle’s shell which is made up of 50 different bones. On the underside of the carapace are the turtle’s ribs, which is the point where the soft tissues fuse to the shell.

Plastron – The lower part of the shell is called the plastron, and this is fused to the carapace along the edges. There are, however, openings for the head, tail, and limbs.

Scutes – Scutes are the hardened structures that cover the carapace, and they can be different shapes and sizes depending on their location. For example, down the middle of the carapace, we find the vertebral scutes, while towards the edge of the shell are the marginal scutes. Scutes are often used to tell one species of sea turtle from another.

Eyes – At the corner of the eyes, sea turtles have a special salt excretion gland that allows them to get rid of excess salt. When they do this, it almost looks as though they are crying, but without the ability to do this, their kidneys wouldn’t be able to cope with the salinity of the sea water they drink.

Nares – Nares is the term given to the paired openings on the nose of the sea turtle, more commonly referred to as nostrils.

Mouth & Beak – Sea turtles do not have teeth. Instead, they have a beak that is made from the same thing as your hair and fingernails; a protein called keratin. They use this beak to grab their food, allowing them to tear or crush it. In the case of the leatherback sea turtle that feeds primarily on jellyfish, there are spines inside the mouth that stop the jellies from sliding out.

Front Flippers – The bones of the sea turtle have separate digits, but these are fused together by soft tissues that make up the front flippers. They move these in a figure-of-eight pattern in order to move themselves through the water.

Rear Flippers – While the front flippers are used for propulsion, the rear flippers keep the turtle stable while it swims, as well as helping it to change direction. During nesting, the female will use her rear flippers to dig a nest.


Sea turtle diet

The diet of the sea turtle is dependent on its species, and this is largely to do with what food is available. Since sea turtles are found all over the world, the things available to them can greatly differ. For example, green sea turtles mainly feed on algae and seagrasses, but in the first few years of their life, they may favor things like zooplankton.

On the other hand, the leatherback sea turtle is famous for its diet of jellyfish, something that many other creatures couldn’t manage because of that sting! However, these turtles are also known to consume things like octopus and squid. The olive ridley sea turtle also eats jellyfish, but its diet consists of things like molluscs and algae as well; talk about balanced!

Some sea turtles, like the loggerhead, are completely carnivorous, while others, like the hawksbill, start off eating crabs and fish eggs but move to a diet of primarily sponges as adults. Again, this depends on the location, as those in the Indian Ocean may not sway from their juvenile diet much at all.

Sadly, all sea turtle species are at risk of eating plastic, as plastic pollution is a serious problem in our oceans. In fact, according to the WWF, it’s believed that as many as 52% of all sea turtles have ingested plastic at some point, as they mistake it for a jellyfish.


Predators of sea turtles

Looking at those hard shells, it would be difficult to believe that anything could eat a sea turtle, but these animals do have plenty of predators. While killer whales have been known to prey on sea turtles, their main predators are sharks.

Tiger sharks will often go for sea turtles, and in areas where there are crocodiles, these also pose a threat.

However, it’s the hatchlings that are most at risk of predation, especially as they make their way from the nest to the ocean. Animals like racoons and sea birds are a particular threat, as well as the sneaky ghost crab.

Even before the eggs have hatched, they’re at risk of being eaten since things like dogs, mongooses, and armadillos will all dig up the nest in search of a tasty snack.


The longest-ever sea turtle migration took 647 days and was completed by a female who swam more than 20 miles (32 km) a day, covering a whopping 12,744 miles (20,509 km) from Indonesia to Oregon.

The longest-ever sea turtle migration took 647 days and was completed by a female who swam more than 20 miles (32 km) a day, covering a whopping 12,744 miles (20,509 km) from Indonesia to Oregon. While this might seem like a massive distance, it isn’t uncommon for sea turtles to migrate over thousands of miles to reach feeding or breeding grounds.

Each breeding season, turtles will return to the place they were born to nest. There is no clear way of knowing how turtles manage to navigate back to their home beaches, although scientists do have some ideas. It could be to do with the magnetic field of the earth or the ocean currents as well as the chemistry of the water.

The leatherback sea turtle travels the most miles each year, and they’re one of the longest migratory species in the world. Each migration could see an individual traveling more than 10,000 miles (16,093 km) as they go in search of food. But the loggerhead turtle isn’t far behind as it makes the annual trip from Japan to Mexico which spans more than 8000 miles (12,874 km)!

Sea Turtles Species

Out of the 240 species of turtles found on earth, seven of them are marine turtles. Let’s take a closer look at each one.

1. Green Sea Turtle (Chelonia mydas)

The green sea turtle (Chelonia mydas) is an endangered species that is named because of its greenish fat and cartilage.

The green sea turtle is an endangered species that is named because of its greenish fat and cartilage. While the shell can be green, it is mainly brown or gray in color and there are distinct yellow and brown markings on the head, making this one of the most beautiful sea turtles.

Green sea turtles are the only herbivorous type of marine turtle, and they feed mainly on seagrass and algae. They’re most commonly found in tropical and subtropical waters and are particularly abundant on the coasts of countries like Turkey and Cyprus. Although their breeding grounds are found as far as 40º north and 40º south so they’re pretty widespread.

Despite this, the green sea turtle is under threat from all angles being at risk of hunting, entrapment in fishing gear, and because of a loss of nesting sites. Moreover, living for up to 100 years, these turtles don’t become sexually mature until between the ages of 20 and 50 years.

They have heart-shaped shells and can grow quite large, with adults weighing up to 400 lbs (181 kg) and measuring up to 47 inches (119 cm). You’ll usually find this species in shallow coastal waters, where it uses its serrated jaw to chew seagrass.

2. Loggerhead Sea Turtle (Caretta caretta)

It’s easy to spot a loggerhead turtle thanks to their thick, broad heads, which is where they take their names.

It’s easy to spot a loggerhead turtle thanks to their thick, broad heads, which is where they take their names. These vulnerable turtles have such large heads to house their strong jaws, which they use to help them crack open the crustaceans that serve as the main part of their diet. 

Loggerhead sea turtles are the most abundant species found in the United States, and they’re also incredibly common in the Mediterranean. However, they are found all over the world and are well known for their annual migration between Japan and Mexico.

Around the same size as the green sea turtle, this species gets to around 400 lbs (181 kg) as an adult and can measure up to 48 inches (122 cm). It has two claws on the ends of each of its flippers, and the shell is usually a murky brown color.

But the loggerhead turtle needs protecting as numbers are rapidly declining. In fact, in one study between 1998 and 2007, it was noted that the population declined by as much as 40%.

3. Leatherback Sea Turtle (Dermochelys coriacea)

The leatherback sea turtle holds the record for being the largest species of marine sea turtle.

The leatherback sea turtle holds the record for being the largest species of marine sea turtle and the biggest ever recorded grew up to 10 feet (3 meters) in length. Typically adults weigh around 500 to 1500 lbs (227 to 680 kg).

Another reason that the leatherback sea turtle stands out is its ability to dive much deeper than other species. In some cases, they have been known to go as far as 3000 feet (914 meters) below the surface in search of food, and the main part of the diet is jellyfish.

In order to prevent the jellyfish from slipping back out of their beaked mouths, leatherback sea turtles have backward spines that line the inner part of the mouth.

They’re also amazing travelers and on average, will migrate as far as 3000 miles in order to get back to their original nesting grounds. Leatherback sea turtles are able to handle much colder waters since they can regulate their own body temperature. While they’re common in warmer parts of the Indian, Pacific, and Atlantic Oceans, they’re found as far north as Alaska. Still, they are listed as vulnerable by the IUCN Red List. 

Instead of the bony scales that we see on most turtles, the leatherback has a leathery skin covering its shell, which is where it gets its name. The shell is usually black but may have pink, blue, or white markings.

4. Olive Ridley Sea Turtle (Lepidochelys olivacea)

The olive ridley sea turtle is the most abundant sea turtle in the world, but sadly it is still listed as threatened.

The olive ridley sea turtle is the most abundant sea turtle in the world, but sadly it is still listed as vulnerable. This is largely due to accidental capture in fishing nets but also because the species is hunted for its meat and skin. 

Olive ridley sea turtles are found in tropical waters and usually prefer to spend their time in the open ocean, whereas many other species tend to stay closer to the coast. They are omnivores that have a balanced diet of fish, algae, crustaceans, and many other things.

These sea turtles don’t live as long as some of their cousins, with adults usually lasting around 50 years. During this time, they will grow to around 100 lbs (45 kg) and get to about 2.5 feet (76 cm) in length. They have two claws on each of their flippers and have an olive green shell, which is where they take their name from. That said, those that are found in the Atlantic Ocean tend to have a slightly darker color than those in the Pacific.

5. Hawksbill Sea Turtle (Eretmochelys imbricata)

The hawksbill sea turtle takes its name from its raptor-like beak, which is perfectly designed for taking pieces of sponge; the primary part of this turtle’s diet.

The hawksbill sea turtle takes its name from its raptor-like beak, which is perfectly designed for taking pieces of sponge; the primary part of this turtle’s diet. Sea sponges are made up of lots of tiny needles, and it takes a special kind of mouth to be able to pick them apart. As well as sponges, the hawksbill turtle also likes to feed on sea urchins and sea grass.

This is a critically endangered species that is found in tropical waters, including bays and lagoons and is frequently spotted around Florida. However, the hawksbill has a stunning mosaic-like shell with serrated edges and overlapping scales, which makes it a target for hunting, especially in Europe and Asia, where the shells are used to make jewelry and accessories.

Hawksbill turtles are relatively small compared to their cousins and usually weigh between 100 and 200 lbs (45 and 91 kg) when fully grown. They can consume up to 1200 lbs (544 kg) of sponge in one year and grow to around 30 inches (76 cm) in length. 

6. Kemp’s Ridley Sea Turtle (Lepidochelys kempii)

The rarest type of sea turtle is the Kemp’s Ridley sea turtle which was named after Floridian fisherman and naturalist, Richard Kemp.

The rarest type of sea turtle is the Kemp’s Ridley sea turtle which was named after Floridian fisherman and naturalist, Richard Kemp. These are small turtles that typically grow to around 30 inches (76 cm) and weigh between 85 and 100 lbs (39 and 45 kg ) as adults.

The Kemp’s Ridley sea turtle is found in coastal shallow waters and has earned its critically endangered status because of its lack of nesting grounds. In fact, this species only has one nesting ground in Mexico, and there are thought to only be 1000 nesting females left in the wild.

These beautiful marine turtles feed on a diet that mainly consists of crabs and other crustaceans, and they have an olive to brown heart-shaped shell.

7. Flatback Sea Turtle (Natator depressus)

The flatback sea turtle is the least endangered of all the marine turtle species since it rarely gets caught in human nets and is not hunted for food.

The flatback sea turtle is the least endangered of all the marine turtle species since it rarely gets caught in human nets and is not hunted for food. That said, we can’t be 100% sure of the numbers as the species is listed as data deficient.

We do know, however, that this turtle has the most limited range of all marine species and is only found in the coastal waters of northern Australia. However, sometimes, they are known to swim as far as Papua New Guinea in search of food. These turtles have a varied diet of sponges, coral, shrimp, and other soft prey.

Flatback sea turtles take their name from their flat shells, which can grow up to 3.2 feet (98 cm) in length, and individuals can weigh up to 200 lbs (91 kg). Although the females are usually larger than the males.

These turtles don’t go too far out to sea, and they prefer areas with soft bottoms. They like to spend most of their time at the surface and even provide a landing space for migrating birds to take a rest. However, they have to be careful when swimming as their shells are much thinner than other sea turtles, and the keratin is incredibly fragile.

Threats Facing Sea Turtles

Threats facing sea turtles

Turtles are among the most threatened animals on the planet, and it’s believed that as many as 61% of all turtle species, including marine turtles, are under threat or already extinct. There are several reasons for this, including a loss of habitat, hunting, and climate change, to name a few.

Habitat Destruction

Habitat destruction is a problem that many animals face, and the sea turtle is no exemption. As you now know, these creatures depend on the beaches for nesting but with more and more human development in coastal areas, these natural areas are being encroached upon.

And it isn’t just the development of houses and other buildings, things like coastal armor are a real issue. These structures are built to protect the shoreline from erosion, and while they’re effective, they are also causing the loss of lots of natural ecosystems. What’s more, on the opposite side of these barriers, erosion could speed up, which again results in the loss of habitable nesting space.

Tourism causes a major issue for sea turtle habitat especially where things like water sports are concerned. Jetties and inlets are built allowing humans to sail and take part in recreational activities but these can reshape the beach with erosion, spoiling the habitat of these turtles. Moreover, with beach furniture like chairs and sun loungers scattered along the shore, this takes up a lot of space that would otherwise be used by the turtles. 

Plastic Pollution

There is an alarming amount of plastic in our oceans, and the problem only seems to be getting worse. While there are schemes in place to try to protect our waters, plastic remains a huge issue, especially for animals like sea turtles. 

Imagine being a sea turtle spotting a floating jellyfish in the water; you’d gobble it right up, wouldn’t you? But then imagine that that jellyfish wasn’t what it seemed; it was in fact a plastic bag. This is the reality for sea turtles all over the world and when they ingest plastic, it can block their digestive systems, choke them, poison them, and ultimately kill them.

Even as they emerge from their eggs, hatchlings are faced with the risk of getting tangled in plastic that lies on the beach. This same debris is catching turtles in the water and trapping them resulting in potentially fatal wounds. Discarded fishing nets are among the most problematic items.

Chemical Pollution

If it wasn’t enough that our seas are filled with plastic debris, consider the chemical contamination. Things like oil spills are common, and they are detrimental to the health of all marine life, including the sea turtle.

Quite obviously, if the sea turtles ingest the oil, this can be toxic and can cause all kinds of health problems and be fatal. What’s more, the oil may also get onto the things that sea turtles eat, so even if they don’t ingest it directly, it’ll still get into their systems via their diet.

Moreover, sea turtles follow a very strict cycle from birth to breeding. When the females come back to their nesting grounds covered in oil, there is a very good chance that the oil will be transferred to the eggs, which will be detrimental to their survival right from the off.

It’s not just oil that poses a problem but the thousands of other chemicals, such as those that come from plastic debris and things like pesticide runoff. In one study, more than 4000 chemical compounds were found in turtles around the Great Barrier Reef, and this caused these animals to be in poor health. It’s no wonder when you consider that other studies have shown the detrimental long-term effects chemicals can have on their immune systems

Light Pollution

With lots of coastal development by humans, the shorelines are illuminated at night. It’s under the cover of darkness that the young sea turtles will make their way from the beach back into the water. However, light pollution can disorientate them and cause them to head inland as opposed to towards the ocean.

Not only this, but it has been shown that the nesting attempts of females are much more likely to fail in areas where there is a lot of artificial light. 

Climate Change

Climate change poses a significant threat to the survival of the sea turtle since it can all but dictate the sex of hatchlings. When turtles bury their eggs in the sand, it is the temperature here that determines what sex the hatchling will be. In warmer conditions, the hatchling will be female and with the rising temperatures on Earth, there is a larger female-to-male ratio meaning this could affect future generations’ ability to breed.

What’s more, as temperatures rise, ice caps melt and this causes the sea level to rise. Since marine turtles rely on the conditions of the water to navigate, a rise in its level could throw them off course. Even if they can figure out which way is home, they may be met with much less of a beach than is suitable for nesting as the rising sea level encroaches on the coast.


Sea turtles are hunted for their meat, skin, and shells, but they can also be overfished accidentally. These beautiful creatures often get caught up in fishing nets as bycatch, and this is one of the biggest threats to their survival. 

When they become trapped in a large fishing net, they could be left here for a long time and this inhibits their ability to surface for air. Since sea turtles are air breathers, not being able to do this means certain death from drowning.

Poaching & Egg Collection

In many coastal communities around the world, humans rely on sea turtle eggs as a source of protein. They will gather their eggs but will also hunt adult turtles to harvest their meat. While this happens with many animals, endangered species should be protected. What’s more, the turtles are not gathered humanely and are often taken from the water and left helpless on their backs until they are needed.

In many countries poaching turtles has been outlawed, but there is still a lot of illegal activity, especially in East Asian countries like China and Indonesia. However, there are efforts in place to catch those involved in this. 

In some South and Central American nations, sea turtles are caught and eaten as part of Lent celebrations. However, in light of the fact that they are meat and not fish, petitions have been sent to the Pope to declare them as such and stop them from being eaten.

Some species of sea turtle, such as the hawksbill sea turtle, have beautiful shells that are highly prized so they are hunted for these.

Conservation Efforts to Protect Sea Turtles

Conservation efforts to protect sea turtles

While all sea turtle species are under threat, that isn’t to say that this has to be an ongoing problem. In fact, conservationists, governments, and communities are getting involved to protect these important members of the marine ecosystem and they’re doing it in a variety of different ways.

For example, the most basic yet important thing we can do is monitor sea turtles to better understand their behavior and keep track of them. However, it can be incredibly difficult to attach tracking devices to them, so scientists have come up with ways that they can use the DNA of sea turtles to track their health and behavior. They are doing this through DNA that is shed by the animals in the water, so nobody even has to bother the turtles in the process.

Many countries and coastal communities around the world rely on sea turtles and other marine life for food. According to experts, banning the consumption of these creatures should be done as a last resort as this simply forces people into illegal activity, which can be difficult to monitor. Instead, conservationists are looking to educate and support local communities in the Caribbean to safeguard their sea turtles populations. Moreover, evidence suggests that illegal poaching of sea turtles is on the decline, which shows that education and awareness could be making a significant difference. 

Further education and research can be obtained through sea turtle-watching tours. While tourism is often to blame for the decline in species, these tours give people a chance to get up close and personal with these creatures, expanding their knowledge and even offering care should they stumble upon an injured specimen.

Since light pollution is one of the biggest problems for nesting sea turtles and their hatchlings, efforts are being made to conserve natural nesting spots and keep them out of the light. Many areas, including Florida, have put measures in place to ensure that lighting is controlled around the coast.

But light doesn’t have to be a problem for turtles, at least not while they’re in the water. You see, by introducing the use of LED fishing nets, these lights could serve as a way of guiding sea turtles away from the impending danger of entanglement.

In some parts of the world, the desire to save the sea turtle is so strong that residents themselves are willing to fork out to protect them. Many Asian Pacific countries are keen to donate to efforts that could see households paying up to $80 annually in an effort to save the turtles, and they’re all very happy to do this.

Frequently Asked Questions

Frequently asked questions about sea turtles

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