Where the warm current from the sub-tropical Indian ocean eaters meets the cold Atlantic waters, biodiversity flourishes. South Africa’s marine biodiversity is quite spectacular, making the waters very unique. The rich waters attract many marine species, especially turtles. Out of the seven species of sea turtle found worldwide, all but two (the flatback turtle and Kemp’s ridley turtle) visit South Africa. Devastatingly, all five species of sea turtles that occur in South Africa are on the IUCN Red List of Threatened Species.
The reason for the decline in sea turtle populations comes down to the threats they face at every stage in their lives. Tens of thousands of sea turtles are lost each year to overharvesting and illegal trade for their eggs, meat, shell, leather and curios. It is estimated that up to 5,000 turtles are caught each year as bycatch by Indonesian longline vessels alone, that number is incredibly shocking without taking in consideration the rest of the world. Uncontrolled coastal development is destroying and disturbing nesting beaches. Light pollution from coastal properties cause confusion to freshly hatch sea turtles and often become disorientated and head for the artificial light instead of out to sea. This puts their already vulnerable life stage at greater risk of predation. Climate change also threatens sea turtle species as global warming could skew sex ratios, resulting in more females.
Sea turtles belong to the family known as Chelonionidea and part of the order Testudines, which includes tortoises, terrapins and freshwater turtles. Fossil records reveal how sea turtles existed long before most other reptiles that inhabited the earth, including snakes and even crocodiles.
Loggerhead (Caretta caretta) nest in KwaZulu-Natal and is carnivorous, feeding on starfish, urchins and molluscs. It is the largest hard-shelled species of sea turtle, weighing up to an impressive 450kg! Despite its large size, this turtle gets its name from its large shaped head. Loggerhead turtles found in the Atlantic and Mediterranean Sea are descendants of the South African Loggerhead turtle.
IUCN RED LIST – ‘Vulnerable’ to extinction and population is decreasing.
Leatherback (Dermochelys coriacea) nests in KwaZulu-Natal and its preferred prey is jellyfish. This turtle can weigh up to a whopping 650kg! Though it is the fastest moving reptile (35km per hour) and can dive up to depths of 1.5km, making it the deepest diving turtle species. Records of this species of sea turtle show that they can live past 100 years old in the wild. The Leatherback turtle is the only turtle to not have a hard carapace, unlike the Loggerhead with a hard carapace. An interesting fact about Leatherback turtle is sunlight shines through their skull onto their brains, which helps the turtle to navigate and know when its time to migrate.
IUCN RED LIST – ‘vulnerable’ to extinction and population is decreasing.
Green turtle (Chelonia mydas) resides in South African waters but is found globally. It is the most widely distributed sea turtle and nests in 80 countries. This is an herbivorous species of turtle and graze on plants and algae. It is much smaller than the other two turtles mentioned above and can weigh up to 395kg. The Green sea turtle uses the earth’s magnetic field to navigate through the waters.
IUCN RED LIST – ‘Endangered’ and population is decreasing.
Hawksbill (Eretmochelys imbricate) usually enters South African waters as strays. These small sea turtles, weighing up to 80kg and use their unique shaped beak to hunts crabs and prawns. The curved beak is where they got their name from. This clever little turtle is immune to the poisons of sea sponges and jellyfish, and stores toxins in its flesh, making it poisonous to their predators.
IUCN RED LIST – ‘Critically Endangered’ and population is decreasing.
Olive ridley Turtle
Olive Ridley (Lepidochelys olivacea) enters South African waters as strays, like the Hawkbill. This tiny turtle can weigh up to on average 35kg and feeds mostly on sea sponges. The Olive Ridley sea turtle displays a behaviour called arribadas, this is where hundreds of thousands of turtles all nest on a beach at the same time.
IUCN RED LIST – ‘Vulnerable’ to extinction and population is decreasing.
Want to find out more… of course you do… scroll down for more interesting facts!
Sea turtle shells are actually made out of bone
Even though we refer to them being ‘shells’ they are actually made up of bone. This hard-outer layer of bone, known as ‘carapace’ is modified bone from the turtle’s spine and ribs. These bones are covered in a layer of skin, which grows into a layer of armoured plates called ‘scutes’. These form the unique pattern on each turtle, except for the leatherback which do not grow scutes. Scutes are made up of keratin, just like the protein that makes up our nails and hair in humans or the horns in rhinos. On the underside of the turtle, the ‘plastron’ known as the belly shell is made up of flat bone plates. The plastron is covered in a membrane called periosteum, which is living bone tissues that humans also have but internally.
Tickle a turtle
Who knows if sea turtles are ticklish? We do not suggest that you do however, a series of nerves run throughout the shell which allows turtles to feel anything that touches them.
Sea turtles need to drink water like us, and dehydration kills many of the Capes stranded hatchlings. Turtles are adapted to drink water from the ocean. As they feed on their food source, they gulp down water with it each swallow and excrete the salt through special glands near their eyes. This gives the appearance of crying, and it is not actually their tears.
Just keep swimming
Sea turtles swim over incredibly long distances during migration. Loggerhead turtles can migrate over 10,000 km a year and Leatherbacks reach over 16,000 km. Within a single lifetime, one turtle could easily migrate up to millions of kilometres.
Taking a few ‘Z’s’ under the sea
Sea turtles need to breathe air and return to the surface regularly to breathe. With a single breathe they can hold it for very long periods of time under water when foraging or hunting. In fact, they can hold their breath up to 7 hours at a time which gives them enough time to have a rest and sleep in sheltered areas on the seabed.
Nesting on land
Like other reptiles, their offspring must surface to take a breath of air and their first breath is taken as soon as they hatch. This is why sea turtles lay their eggs on sandy beaches, so their offspring does not suffocate as oxygen cannot permeate through the shell to the foetus if it is under water. South African loggerheads and leatherbacks nest of KwaZulu-Natal sandy beaches. Their nesting season begins when the shift in the Agulhas Current brings in warmer waters to the South African coast, between October and February.
Sea turtles are able to migrate back to the exact beach they hatched from by using the earth magnetic field to navigate their way back. They have tiny crystals called magnetite, which are magnetic and act like a compass. Loggerheads can sense rocks underneath the sands of its nest, making a ‘magnetic fingerprint’ that they remember forever.
The ‘Lost years’
This refers to the early stages of the turtle’s life, the ‘lost years’. After they crawl from their nests and make their way to the ocean the fight for survival begins. Very little is known about the journey up into their sub-adult years and the true dangers these little turtles face. Loggerhead turtles have a ‘lost’ period as long as 7 to 12 years long, and from them they reappear as large sub-adults.
The vulnerable little turtles will swim up to 20 hours in the open waters of the ocean to avoid predators, avoiding the shoreline as far as possible. They rest on floating seaweed beds and the natural currents to conserve their energy.
Let’s save the turtles!
If globally we all came together to join in the fight to protect sea turtles, making sustainable choices and ethical choices we could help save our sea turtles from extinction. It is important for people to buy sustainable seafood products, ensure that they are certified as being sustainable and increase the demand for sustainable fish in our shops and eliminate the demand for cheap, unsustainable fish.
When travelling, be cautious of the products you are buying, avoid buying products made of turtles and avoid eating their meat. Do not be afraid to question the origin of the product. Other ways to help sea turtles include supporting sea turtle ecotourism. Ecotourism benefits wildlife conservation in many ways and helps to support local communities. Eco tourism can in fact help fun for conservation projects and highlights the importance and benefits to saving the species, and protecting it in its natural habitat, therefore not killing them or exploiting them for money.
Across the world, we are trying our best to reduce our plastic waste. It is estimated 1,000 turtles die each year due to plastic waste polluting our oceans. Therefore, make the switch from single-use plastic to other sustainable and environmentally friendly products. Recycle, reduce and reuse and together we can reduce our negative impact on our marine life and the planet.
Come back next Friday for more interesting facts, #factfriday !