Sighting sea turtles on a dive is a unique and unforgettable experience.
But knowing some of its characteristics and behavioral peculiarities can make the encounter even more fascinating.
Origin of Sea Turtles
Sea turtles are living representatives of a group of reptiles that have existed on Planet Earth and have roamed our seas for the last 100 million years.
They evolved from freshwater turtles, although they differ from them by having flippers that attach their toes instead of legs to adapt to life primarily in the sea.
These powerful, paddle-like flippers and their more streamlined shells help them swim quickly and make extensive migrations.
Sea turtles also lost the ability to retract their limbs (head, flippers, and tail) into their carapaces.
Types of Sea Turtles
Seven different species of sea turtles grace our ocean waters, from the shallow seagrass beds of the Indian Ocean to the colorful reefs of the Coral Triangle and the sandy beaches of the Eastern Pacific.
- Loggerhead (Caretta caretta)
- Green turtle (Chelonia mydas)
- Leatherback (Dermochelys coriacea)
- Hawksbill (Eretmochelys imbricata)
- Kemp’s ridley (Lepidochelys kempii)
- Olive ridley (Lepidochelys olivacea)
- Flatback (Natator depressa)
Where do Sea Turtles live?
They have a very wide range of distribution, inhabiting oceans and tropical and subtropical seas throughout the world.
Depending on the species, turtles migrate thousands of miles throughout their lives across ocean basins and offshore between feeding grounds and nesting beaches.
One Leatherback turtle traveled more than 12,000 miles (19,300 km) round trip across the Pacific Ocean from Papua in Indonesia to the northwest coast of the United States.
How long do Sea Turtles live?
Sea turtles live a long time (some can live up to 50 years or more) and have life cycles similar to humans.
Most take decades to mature (between 20 and 30 years) and remain actively reproductive for another 10 years.
They come in many different sizes. The smallest (Kemp’s ridley) can grow up to 0.6 meters and weigh 60kgs while the largest, the leatherbacks, can reach 2 meters and weigh 900kgs.
Sea Turtles eggs: Reproduction
Sea turtles reproduce sexually and are oviparous, laying eggs from which hatchlings are born.
After mating with males in the ocean, females go to the beaches (usually at night), build their nests, and lay their eggs.
When they finish covering the nests with sand, the females return to the sea.
See Turtle: Nesting season
Sea turtles are solitary creatures that remain submerged in the sea most of the time and rarely interact with other living beings, outside of courtship and mating.
One of the exceptions to this behavior is a wonderful phenomenon called “arribada” when thousands of Olive Ridley sea turtles nest at the same time and on the same beach in Costa Rica.
Different species of sea turtles exhibit various levels of philopatry. In extreme cases, females return to the same beach where they hatched. This can take place every two to four years in maturity.
In a single nesting season, females, depending on the species, may lay between two and six clutches of eggs, each with 60 to 180 eggs.
The hatchlings take 45 to 75 days to hatch, but since it is the temperature that will determine the speed of embryo development, the timing of hatching can vary. Basically, the warmer the sand around the nest, the faster the embryo will develop.
Global Warming Impact
Temperature also determines the sex of the turtle: within the same nest, eggs in the periphery are more likely to be male, while those in the center are more likely to be female.
Nests exposed to very high temperatures will produce only female hatchlings. This is one of many reasons why global warming impacts the vulnerability of these species.
How many baby Sea Turtles survive?
Only one out of every 1,000 turtles that hatch from eggs reaches adulthood.
Predators such as crabs, foxes, and birds feed on the hatchlings, which they capture during their short but difficult journey from their nests on the beach to the sea.
Conservation Status and Threats
The IUCN Red List classifies three species of sea turtle as either “endangered” or “critically endangered”.
An additional three species are classified as “vulnerable”.
The flatback sea turtle is considered “data deficient”, meaning that its conservation status is unclear due to lack of data.
All species of sea turtle are listed in CITES Appendix I, restricting international trade of sea turtles and sea turtle products.
This alarming state of conservation is mainly due to human activities.
Bycatch in fishing gear, which often results in death, is the greatest threat to most sea turtles. Sea turtles must surface to breathe. Caught in a fisherman’s net, they are unable to surface and thus drown.
They are also killed for their eggs, meat, skin, and shells, and are victims of poaching and overexploitation.
In addition, climate change affects the nesting beaches of sea turtles as well as their eggs.
When turtles hatch from their eggs on the beach, they are already endangered with plastic.
Turtles have to find the ocean by themselves and on their journey from land to sea, they encounter a lot of plastic. Some even get trapped in plastic and die from lack of resources and from the sun being too hot.
Diving with Sea Turtles
Sharing the ocean with a turtle can be a breathtaking experience. The way they move underwater is unique.
However, turtles are shy animals. As mentioned before, they are solitary and they are not able to retract their heads inside their shell to hide.
For this reason, we need to be aware that when we are diving or snorkeling with turtles, it is crucial to keep our distance from them (as with every species!).
Blocking their swimming way up can delay their time to get to the surface to breathe or obliged them to move in another direction that could be harmful. Getting too close on the surface can force them to shorten their breathing time.
So remember to keep your distance, avoid trespassing in their ways, and do not flash your cameras in their face!
If you are a marine life lover, stay tuned for more posts to come about this and many more species!
And for those who would like to become experts take the challenge and enroll in our Sea Turtle Ecology Specialty.
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