Oct 2017

Sea Turtles – All You Need to Know

By Roya Eshragh

Relatively speaking, there aren’t that many species of marine reptile you are likely to run into on a dive. However, their charisma, curiosity, majesty and of course love they elicit is enough to fill every single ocean on earth.  Similar to their terrestrial cousins, they are evolutionary dinosaurs, changing very little in the aeons of their existence. For centuries, this ancient form served them perfectly, but even with the love of modern ocean-goers, they are now finding survival in this human age increasingly more perilous.

Let’s get to know what these majestic creatures are all about.

How many types of Sea Turtle are there?

There are seven types of known sea turtles in Earth’s oceans. Six out of those seven species are endangered, due to the brutal activities of mankind. We must learn to live with these magnificent sea creatures or face losing them altogether.

What are the different types of Sea Turtle?

  • Hawksbill
  • Loggerhead
  • Green Turtle
  • Leatherback
  • Kemp’s Ridley
  • Flatback
  • Olive Ridley

Where can you find Sea Turtles?

You can find sea turtles all over the world in each and every ocean. Below is our list of top 15 most places and diving locations to find sea turtles are as follows:

Sea Turtles – the Top diving locations to see and swim with them

  1. Ari Atoll, Maldives
  2. Galapagos Islands, Ecuador
  3. Apo Island, Philippines
  4. La Flor Wildlife Refuge, Nicaragua
  5. Fiji Islands
  6. Mnemba Island, Tanzania
  7. Sipadan, Borneo, Malaysia
  8. Muscat, Oman
  9. Tortuguero National Park, Costa Rica
  10. Maui Island, Hawaii
  11. Siladen, Indonesia
  12. Gili Trawangan Island, Bali
  13. Alphonse, Seychelles
  14. Playa del Carmen, Mexico
  15. The Great Barrier Reef, Australia

How long do Sea Turtles live?

The average age of a sea turtle is between thirty (30) and fifty (50) years. However, they have been known to live much longer, with some recorded sea turtles living as long as 150 years!

Sea Turtle reproduction

These migratory species are found across the oceans but are typically born on tropical and subtropical shores. In fact, unlike freshwater turtles who are prone to sunbathing on stable ground or emerging logs, sea turtles never step flipper on land except for when they are hatching, or when they return to lay eggs.

Famously, sea turtles return to their natal beach to lay the next generation. The female crawls up onto the shore and uses her large flippers to dig a hole big enough for anywhere between 50 and 350 eggs. She then will kick sand back over the eggs, completely disguising the nest. This whole process can take upwards of 60 minutes. She can do this up to 8 times per season.

Sea Turtle eggs

Where the eggs are placed has an indirect impact on the sex of the offspring. Sex in turtles, alligators, and crocodiles is determined after fertilization by the temperature at which the eggs are incubated. Only a few degrees can make all the difference. Any egg incubated below 81.86°F (27.7°C) will become male.

Eggs incubated above 87.8°F (31°C) will become female. Eggs incubated between the two temperatures will become a mixture of male and female. Because global temperatures are on the rise, and even the deepest sand temperatures are following that trend, this could have vast impacts on sex ratios.

After about 50-60 days, the eggs will hatch and the babies will make a run to the relative safety of the sea. This is historically the most dangerous time in the entirety of a sea turtle’s life. On average, one egg from each clutch will make it to adulthood. Birds, snakes, dogs, racoons, crabs, and fishes will prey on the small and vulnerable young.

Some species, such as the Kemp’s Ridley and Olive Ridleys will try to combat these odds by overwhelming the predators with numbers. Hundreds to thousands of sea turtles will nest at once so all the young hatch simultaneously. With thousands of baby sea turtles making sprinting to the sea, predators can’t possibly capture all of them and some have a greater chance of making it to safety.

Eggs that never hatch will decompose and provide important nutrients to the beach communities and dune vegetation. The plants that they nourish create important erosion control for fragile beach ecosystems. Once the hatched turtles have made it to the open sea, the young of almost every species are vegetarian. They feed on seagrass and algae and help keep seagrass beds biodiverse and healthy.

Sea Turtle anatomy

Instead of a shell, they have a carapace on their backs and a plastron on their bellies. Because they essentially spend the entirety of their life swimming in the water, they are more fusiform than terrestrial turtles. But, to become so fusiform, sea turtles had to lose the ability to retract their legs and neck.

The resulting effect is that sea turtles can migrate thousands of miles every year but they cannot protect their appendages, in the same way, a terrestrial turtle can. As the turtle ventures around the ocean, it does pick up some unexpected company. Up to 29 species of sea turtle-specific barnacles live off the literal backs of these nomadic reptiles.

Just like the barnacles embedded in whale’s skin, the small arthropods attach themselves to the carapace or plastron, and sometimes even the flippers of sea turtles, capitalizing on the microplankton feast in all the waters the sea turtle host visits. There isn’t any evidence these barnacles hurt their hosts, mostly the turtles don’t seem to notice the barnacle’s presence.

What turtles most certainly notice is the higher presence of salt in marine environments than those of their freshwater ancestors. To compensate for the higher salt concentration outside of the body, many vertebrates like fish and mammals produce high salt concentration urine to rid the body of excess salts.

However, reptilian kidneys are not capable of doing so; instead, they have a lachrymal gland near their eyes that produce incredibly salty tears. So if you’ve ever seen a sea turtle or other marine reptile appear to sneeze or shake their head violently, they are probably releasing these salty drops and expelling them far from their face.

How far do Sea Turtles migrate?

Some sea turtles do not travel far at all, whilst like the Leatherback is one of the most migratory species on the planet. The Leatherback has been known to travel over 10,000 miles (16093.44 km) each year to search for highly yielding grazing areas in their search of food.  They have been known to travel from the beautiful warm ocean down on Caribbean beaches all the way up past the USA East coast and to the colder Canadian waters. That is one long way to go just to find a meal!

How long do Sea Turtles breed?

Sea turtles can take up to 50 years to reach sexual maturity. They mate in the sea while staying afloat to breathe. The females can then swim thousands of miles to return to the beach of their birth and start the cycle all over again. Once mature, they mate and lay eggs every 2-4 years.

This will continue until they breathe their last, somewhere around 80 years. So the low survival rate per clutch, combined with the relatively small breeding potential throughout a turtle’s life make them a vulnerable group to changes in the ecosystem or unnatural predation. They cannot replenish their number quickly should a large disturbance take place.

What are the major threats to Sea Turtles?

The main threats to sea turtles are as follows:

  • Old fishing lines
  • Caught in plastic rings/ can holders
  • Plastic bags (mistaken for food)
  • Fishermen / Hunters for eggs and meat
  • Oil spills
  • Human development on beaches

Unfortunately, that is just what is happening to their number, from almost every angle. Not only are sea turtles poached for their meat, leathery skin, and shells, they are often unintentionally caught as bycatch. This means that they get stuck in nets, long lines, and trawls meant for other species. Because turtles are reptiles, they must come to the surface to breathe air. When they are caught in fishing gear, they cannot make it to the surface in time and drown.

Even if a turtle remains free its entire life, it is sure to be affected by human waste. Plastics are found in every ocean at this point, and many look and smell like food to an unsuspecting sea turtle. Once ingested, the plastic never breaks down. Instead, it perpetually takes up space in the turtle’s digestive system, blocking nutritious food from being digested and absorbed. So turtles will starve because their bellies are too full. Turtles can also get caught in plastic rings, causing deformations while the turtle grows.

Oil spills are especially disastrous for sea turtles of all ages. Oil tends to float, so when a turtle comes to the surface to breathe, it is coated in the oil. While they attempt to take in air through their nostrils, the oil is inhaled and ingested as well. The inside of their lungs and digestive tract is covered in oil, eventually causing it to become so sick it can no longer swim. Female sea turtles can pass oil compounds on in their eggs, and oil that reaches nesting beaches can penetrate into the eggs of the unborn turtles.

Speaking of eggs on nesting beaches, they have been facing novel threats in the past century from human development. As the coasts become developed for human use, sand is disturbed, inaccessible, or eliminated entirely. Females have nowhere safe to lay their eggs, and eggs that are lain are vulnerable to human activity overtop of them. Seagrass beds and mangroves, traditionally used as nurseries for the young turtles, are disappearing at alarming rates. It is no wonder that every species of sea turtle is listed on the IUCN endangered list.

Running into a sage, unbothered sea turtle on a dive is always a delight. However, it is only going to become rarer of a thrill the worse we treat the oceans. Or perhaps most importantly, the worse we allow the oceans to be treated.

written by Roya

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Roya Eshragh

Even as a little girl, I was obsessed with the oceans and wanted to become a marine biologist. So, I got into diving in 2011 as an aide for my Master’s research on cephalopod (squid, cuttlefish, octopus, etc) parasites. I completed my PADI Open Water course and continued with the CAUS Scientific Diver course in the cold cold waters around Vancouver BC. When time allowed, I would help with the Howe Sound Research Group of the Vancouver Aquarium monitoring the Sound. I’m sorry to say, but even after all that, I still haven’t quite come to love dry suit diving.

Once I moved to Madagascar as the Science Officer of a marine conservation NGO, I realized just how lovely diving in the tropics could be. There, I completed my DiveMaster and became addicted to daily diving. I had to find a way to continue! So I did my IDC in Bunaken, Indonesia, completing my MSDT course and learning the tricks of the trade on a few inaugural students.

Currently, I am a dive manager/reef ecologist in Sri Lanka and starting up a conservation and education program with my dive shop. Combining my love of the oceans with my love of science, I am thrilled to have found a way to bridge the two and teach others about this incredible ecosystem we still don’t know nearly enough about. There’s still lots more for me to learn, both about diving and about the marine world, and that is the beauty of it all!

Qualifications:
PADI Specialty Instructor
CAUS Scientific Diver 1
Master of Science - Zoology

Dream Dive Locations:
Komodo, Indonesia
Silfra, Iceland
Maldives
Wreck Diving, Lake Michigan

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