Right, let’s start with the facts.
All tortoises are turtles, but not all turtles are tortoises.
But what does this even mean?
Oftentimes, many people use the two words interchangeably. However, this is incorrect.
Unlike tortoises, which spend the majority of their lives on land, turtles are found in freshwater or marine environments. Marine turtles spend nearly all their lives in the ocean, only coming to shore to lay their eggs. In Costa Rica, there are thought to be 14 species of turtle – 5 marine turtles and 9 freshwater turtles.
In this article, we’ll be exploring exactly what a turtle is and the different species of marine turtles that can be found in Costa Rica. I have worked with 4 of the 7 species of sea turtle found across our globe, aiding with vital scientific data collection. In other words, I know a thing or two about sea turtles.
What (Exactly) Is A Turtle?
A turtle is a type of reptile that has its body encapsulated within a bony shell.
Yes, many animals have shells. In fact, many invertebrates of Costa Rica have shells, including snails, crabs, and marine molluscs.
However, the architectural ingenuity of the turtle shell is what sets it apart.
The shell of a turtle consists of two sections: the top (carapace) and the bottom (plastron). The two sections are made of bone and cartilage.
Unlike other shelled animals, a turtle will not be able to survive without its shell.
Not only is it a vital component in the protection against predation, but the shell of a turtle also contains important anatomical structures, such as their rib cage, spinal cord, blood vessels, and nerve endings.
The shell also acts as an essential reservoir of fat, water, minerals, and waste products.
The top carapace and bottom plastron are fused together at the side of the body, creating what’s known as a skeletal box. This, in part, ensures that the shell of the turtle remains in place and cannot be shed.
Unlike tortoises, which are found solely on land, turtles live both on the land and in aquatic environments – both marine and freshwater.
The anatomical differences between turtles and tortoises will allow you to distinguish between the two groups. Whilst tortoises have stubby legs with distinct claws, turtles have flat, oar-like flippers. These anatomical differences correspond to the particular habitat the animal can be found in – be it the open ocean or on the desert floor.
5 Marine Turtles In Costa Rica
I have had the privilege of working with a range of sea turtle species across the globe.
Sea turtles have a large geographical range and, as such, can be found in a large variety of countries.
I have worked with green and loggerhead turtles in Cyprus. However, I have also worked with green turtles in Costa Rica.
In Costa Rica, I have also worked with olive ridley and leatherback turtles, assisting marine biologists with the collection of geometric data and tagging.
Below are the 5 species of marine turtles that can be found in Costa Rica:
1. Olive Ridley Turtle
Olive ridley turtles are the most numerous sea turtle species on the planet.
In fact, they are so populous, that at certain times of the year, hundreds of thousands can be seen nesting in just one place.
These mass aggregations of olive ridley sea turtles are known as arribadas, or, in English, mass arrivals.
There are 6 known arribada sites in the world, two of which are found in Costa Rica: Playa Ostional and Playa Nancite – both beaches of which are found in the province of Guanacaste, North Costa Rica.
Although arribadas can occur throughout the year, the largest aggregations occur in the rainy season, between the months of September – November. The event is thought to be triggered when the moon enters its final quarter.
Each female can lay anywhere between 70 – 110 eggs. During an arribada, millions of eggs can be laid.
Of course, not all these eggs survive. Many are crushed and destroyed by the continuous onslaught of determined nesting females. Others are predated on by a range of animals, including crabs, Casta Rican birds, and mammals.
Playa Ostional is the only beach in Costa Rica where it is legal for local people to sell turtle eggs for consumption.
But, enough about arribadas. Let’s look at the biology of the olive ridley.
Olive Ridley turtles get their name from their distinct olive hue to their carapace – a colour that develops with age.
As far as sea turtles go, olive ridleys are relatively small. Their distinctive hump-shaped shell measures no more than 70 cm – I spent many sleepless nights collecting shell measurements of olive ridleys.
Once hatched, olive ridleys will spend the vast majority of their life out in the open sea. Here, they forage for a range of food, including fish, jellyfish, and algae. However, not much is known about this stage of the turtle’s life history.
When the time is right, olive ridleys will migrate for thousands of miles to reach the beach where they once hatched to lay eggs of their own. Males, characterised by their longer tail, wait in the shallows and attempt to mate with females as they make the arduous journey.
So, if you need a reason to visit Costa Rica in the rainy, or green season, perhaps the opportunity to spy hundreds of thousands of nesting turtles may just be tantalising enough.
2. Green Turtle
Green turtles are so called not because of the colour of their shell, but the layer of green, fatty tissue under their skin.
In Costa Rica, however, a sub-species of the green turtle can be found: Tortuga negra – or black sea turtle. Unlike their close relatives, this sub-species of green turtle is named after its black shell.
Second only to the leatherback turtle, the green turtle is one of the largest sea turtles in the world. The largest one I measured was on a remote beach called Playa Cabuyal, in Northern Costa Rica. It measured 118 cm (shell length only).
You may think that taking measurements is rather intrusive and stressful for the turtle. But you’d be surprised. When females begin laying eggs, they enter a trance-like state. They become hyper-focused, intent on depositing their future offspring. Only drastic movements will cause a turtle to abandon the egg-laying, and this is when we can collect measurements and biometrics.
After approximately 60 days, baby turtles hatch en-masse, flooding the beach with thousands upon thousands of these tiny reptiles. This is an anti-predatory strategy – after all, safety in numbers.
Young green turtles are omnivorous, preying on small crustaceans, molluscs, and seagrass. However, once they reach adulthood, green turtles lead a vegetarian lifestyle. They feed heavily on seagrass and algae.
Green sea turtles are one of the longest lived vertebrate species in the world, reaching ages of over 70 years.
3. Leatherback Turtle
The leatherback turtle is a record breaker.
Not only is it the largest species of turtle in the world, with some measuring an astonishing 2 meters in length and over 900 kg in weight, but it is also the deepest diver of all marine turtles.
Leatherback turtles have been recorded diving to depths of over 1,000 meters, where they hunt deep-ocean jellyfish.
Unlike other species of sea turtles, which have a hard shell, the leatherback, living up to its name, has a soft, leathery shell. Whilst diving, their flexible shell stores excess nitrogen and can help the leatherback adapt to the high pressure of the deep ocean.
In addition, leatherbacks have a high oxygen affinity. Essentially, this means that they can store high quantities of oxygen in their blood and muscles, allowing them to stay submerged for several hours at any one time.
In Costa Rica, populations of leatherbacks are critically endangered. Once a regular sight in beaches such as Playa Grande, populations have crashed by over 70%.
I worked with an organisation called The Leatherback Trust, which monitored populations of leatherbacks, as well as other sea turtle species. During peak season, just 7 leatherbacks were recorded.
However, populations on the Caribbean side of Costa Rica remain stable. They can commonly be seen in Tortuguero National Park throughout February to August.
4. Hawksbill Turtle
Named after their pointed, hawk-like beak, hawksbill sea turtles are one of the rarest turtle species found in Costa Rica – despite their global distribution around tropical coral reefs.
Their pointed beak allows them to forage a rather unique prey species – sponges. They are one of the few species that can survive primarily on these ancient invertebrates. The narrowness of their jaw allows the hawksbill to access otherwise hard to reach areas.
A resident population of hawksbills can be found in Golfo Dulce; a rare tropical fjord in Southwest Costa Rica. However, due to the deep waters of the fjord, the small size of the turtle, and the conservation status, sightings are few and far between.
Today, the best spots to see wild hawksbills are along the Caribbean coastline, in places such as Cahuita, Gandoca, and Tortuguero National Parks.
Despite their rarity, they are one of the most spectacular species of sea turtles. Their mottled shells are adorned with shades of amber, orange, olive, yellow, brown, and red. Alongside the colourful patterns, hawksbill turtles have serrated edges to the posterior region of their shell.
Because of the uniqueness of their shells, Hawksbills are highly valuable and targeted for their use in “tortoise-shell” jewellery and accessories.
A fully grown adult hawksbill can reach just 80 cm in length, making them one of the smallest extant species of sea turtle.
5. Loggerhead Turtle
Not to judge a book by its cover, but loggerhead turtles are rather peculiar looking.
As babies, they have a large head in comparison to their body, complete with large, bulging eyes. As it matures, their remains almost disproportionately large, giving rise to its namesake.
However, their large heads are an evolutionary adaptation, not some kind of genetic mutation. The large heads of a loggerhead turtle support powerful jaw muscles – the perfect weaponry to help crush their hard shelled prey of clams and sea urchins.
Whilst loggerheads are mostly sighted in the Mediterranean (where I have conducted my research), small populations can be found on the Caribbean coast of Costa Rica.
Between the months of May to October, loggerhead turtles come ashore around the beaches of Tortuguero. Like the hawksbill, loggerhead turtles are quite a rare sight in Costa Rica.
Baby Sea Turtles
Like some reptile species, most notably crocodilians, the sex of a sea turtle is determined after fertilisation.
When laying eggs, a female will create an egg chamber by using her hind flippers. These chambers can be up to a meter deep. The temperature within these chambers influences the sex of the developing offspring. In zoology, we refer to this as temperature-dependant sex determination.
If the egg chamber is 27.7 degrees Celsius or below, turtle hatchlings will become male. Above 31 degrees Celsius, the clutch will be female. Fluctuating temperatures yield a mixed clutch of both males and females.
However, with the current global temperature rise, as a result of anthropogenic climate change, we are noticing that more and more sea turtle nests are producing all-female clutches. With such a massive sex skew, the survival of sea turtles may be in jeopardy.
Deviating ever so slightly off course, a team of scientists in Costa Rica recently discovered a female American crocodile that had given birth to a clutch of eggs – without a male present. This “virgin birth“, known as parthenogenesis, could become an evolutionary strategy that will allow female sea turtles to survive and create new offspring in a male-less world.
Threats To Sea Turtles
Humans. Need I say more?
Many of the current threats sea turtles face are directly attributed to human activity. But, this shouldn’t come as a surprise anymore.
Turtles are at risk from an array of threats – most of which are intrinsically linked.
Take a beachside condo development, for example. Nesting beaches will be destroyed. That’s a given. But noise and light pollution will increase, as will plastic waste from a surge in people. Artificial lights disorientate hatchlings, causing them to travel inland and away from the ocean. Increased tourism will see the addition of water activities, such as boat or jet ski excursions, increasing the risk of collisions.
But, let’s explore in more detail the main threats sea turtles in Costa Rica are facing.
1. Climate Change
Let’s start with the biggest, and perhaps least known.
Climate change is a very real problem that is affecting nearly all life on our planet.
Yet, the science behind climate change is not concrete and the implications climate change will have on sea turtle populations are still being researched.
As we discussed above, climate change is affecting the sex of turtles – with higher densities of females now being recorded.
However, there are some other, indirect problems arising from climate change.
As sea temperatures rise, frequency and severity of tropical storms are likely to increase. It is thought that the power behind these storms can erode vital habitats essential for the survival of sea turtles, such as coral reefs or nesting beaches. Increased rainfall may flood nests, increasing bacterial and fungal infestations, and drastically reducing hatching success rate.
Climate change will affect global weather patterns, which may, in turn, affect the circulation of ocean currents which sea turtles use to navigate and migrate.
Yes, plastic has been a big problem for many years. And what has been done about it? Not much.
Despite claims from major corporations about how they’ve cleaned up their act, it is estimated that over 380 million tonnes of plastic is being produced each year! Much of this is single use plastic that will end up in our oceans.
According to experts, some 500 billion bags are used worldwide. Oh, but its fine, because now many large supermarket chains, especially in the U.K, charge 10p per bag. It is a greenwashing conspiracy that feeds capitalistic greed.
It’s a touchy subject for me, can you tell?
I have witnessed first hand the effects of plastic. Walking along deserted Costa Rican beaches, far from any town, plastic littered the shorelines. Plastic cutlery, footwear, straws, bottles, bags, clinical waste. You name it, I saw it.
In the ocean, plastic is broken down into near microscopic pieces by the UV rays of the sun, and the abrasive action of the waves.
Unfortunately, many marine species – both big and small – consume these microscopic plastic particles, until plastic has made its way up the food chain.
Large predatory fish, such as tuna and sharks, as well as sea mammals and turtles, are the ones that are affected most of all. Known as bioaccumulation, toxins from plastic build up in an organism faster than they can be broken down. The toxins bio-magnify the higher up the food chain they go and can cause serious health problems for a range of animals.
Turtles are significantly at risk from plastic pollution. Not only do they unknowingly ingest microplastics, they actively eat plastic bags – simply because plastic bags look remarkably similar to one of the main prey species of a turtle, jellyfish.
I have carried out necropsies on olive ridley, loggerhead and green sea turtles. In nearly all cases, plastic had been found either lodged within their trachea, causing suffocation, or within the stomach, causing starvation.
Plastic pollution is a global problem. We are simply addicted to it, at the detriment of our planet.
3. Discarded Fishing Gear
Discarded fishing gear, otherwise known as ghost nets, are a serious threat to marine life. Ghost nets include any form of lost or discarded fishing gear, much of which remains unseen.
Ghost nets are a form of plastic pollution, contributing up to 800,000 tonnes of marine waste. It is possibly the deadliest form of marine plastic.
As it floats in the water column, it can snag and ensnare a range of wildlife from marine mammals, fish, seabirds, and turtles. The entangled animals, unable to feed or escape, face a painful death through either starvation, suffocation, or exhaustion.
In the US alone, it is estimated that 250,000 sea turtles become entangled or killed by ghost nets every year.
Discarded fishing gear also damages important marine ecosystems, such as coral reefs, in which sea turtles (as well as a plethora of other marine life) rely on for rest and cleaning.
4. Habitat Loss
When we talk about habitat loss, our minds may wander to rainforest deforestation.
But habitat loss can occur in every ecosystem of our planet – including the ones sea turtles so heavily rely on.
As Costa Rica becomes an ever more popular tourist destination, more and more infrastructure is being constructed to accommodate the increase in tourism.
And what areas are commonly affected? Beaches!
But coastal development is a broad category, encompassing a range of human activities – including the beachfront development of homes, hotels, restaurants and roads. Oftentimes, sea defences are also implemented to protect these new developments, such as sea walls.
Such landscape alterations negatively affect historic nesting grounds, either by destroying the nesting beach completely, or creating barriers that render the beach inaccessible. If a female turtle does manage to nest, beach litter and light pollution can harm hatchlings.
However, coastal development isn’t the only type of habitat loss affecting sea turtles.
Certain fishing practices, such as trawling, destroy seagrass meadows – the critically important foraging grounds of green sea turtles. It is these grass meadows that give the green turtle their characteristically green fat.
Other species of sea turtle, such as the loggerhead, use the seagrass meadows to forage for invertebrate prey.
Bycatch is a global epidemic affecting all megafauna of our oceans.
Put simply, bycatch is the accidental capture of a non-target species. In this case, turtles!
Where there is fishing, there is bycatch.
Across the globe, thousands of miles of fishing lines are deployed each day. Effective though they may be at catching target species, such as fish, they are near invisible in the water column and can snag any animal swimming in their path.
Every day, marine mammals, birds, and reptiles die needlessly, often as a result of drowning via entanglement. For those that are caught and hauled up onto fishing vessels, they are unceremoniously thrown back overboard, weak and injured, and often to their demise.
In the USA alone, it is thought that 12,ooo sea turtles die as a result of accidental bycatch each year. However, the actual figure may be much, much more.
6. Direct Harvesting
Despite being a protected species in much of the world, sea turtles are still commercially hunted for their eggs, meat, and shell.
In Costa Rica, egg poachers are a prevalent problem – an issue I have come face to face with. In fact, a previous colleague, Jario Mora Sandoval, was brutally murdered by poachers on a Costa Rican beach. He was just 26 years old.
Poaching is a ludicrous industry. With each egg selling for $1, and with up to 100 eggs in a single nest, turtle egg poaching is easy money to be made.
However, in Costa Rica, the collection and sale of turtle eggs is illegal and strictly monitored. Only one area, Playa Ostional, is licensed to trade in turtle eggs – and regulations are fierce.
But it’s not just eggs targeted.
Hawksbill turtles were readily hunted for their ornate shells, which were used to create jewellery and tourist trinkets – leading to a near collapse in the Costa Rican population. Fortunately, hawksbill turtles are now listed as a protected species and, under CITIES, it is illegal to trade any turtle products on the international market.
Sea turtles have been roaming the world’s oceans for millions of years. They are one of the oldest living vertebrate species living today.
In Costa Rica, 5 species of sea turtles can be found – all of which are threatened with extinction.
The most common sea turtle, the olive ridley, can be seen on the Pacific shores of Costa Rica in their hundreds of thousands at certain times of the year.
Other species, such as the hawksbill and loggerhead, can be seen infrequently in small hotspots across the Caribbean coastline and a small fjord in the Puntarenas province.
Despite being a much-loved tourist attraction, all species of sea turtles are threatened with extinction. Climate change, habitat loss, and plastic pollution are serious threats negatively affecting sea turtle populations.
However, many conservation groups are conducting important research on sea turtle species. The results will help scientists conserve these ancient reptilian species for generations to come.