Our Projects related to Sea Turtles:

 

Birdsleuth Carriacou

 

Discover Grenada Turtle Tours

Other sources of information on Sea Turtles:

 

Kido Foundation

 

Ocean Spirits Inc.

 

WIDECAST

Sea Turtles

 

Sea Turtles belong to the Class Reptilia, which means they are reptiles and related to animals like crocodiles, snakes, lizards and even dinosaurs. In fact, turtles are some of the oldest creatures on earth, and they have very long lifespans. Some species of sea turtles have been known to live for over a century!

 

Sea Turtles vs. Tortoises

  • Tortoises have high-domed shells that most species can retract their limbs into when threatened. Sea Turtles, on the other hand, have hydrodynamic shells for swimming efficiency, and cannot retract their head or limbs for protection.

  • Tortoises have legs and feet for walking, and are rather slow-moving; whereas Sea Turtles have flippers which can as paddles for swimming and reach great speeds in the water. Like their land counterparts, however, they are still rather slow on land.

 

Characteristics of Sea Turtles

  • Vertebrates, meaning they have a backbone. In all species but the Leatherback, the backbone and ribs are actually fused to their shell

  • Ectothermic, or cold-blooded

  • Air-breathing, so they must come up for air when swimming. However, their adjustable metabolism allows them to stay underwater for long periods of time. Green turtles can hold their breath for 5 hours

  • Very powerful swimmers, because of their strong forelimbs or "flippers". However, this adaptation to make them better swimmers also makes them very awkward on land

  • Possess salt glands which help excrete the salt taken in when they drink seawater. All animals need freshwater to survive, and turtles are no different; they take in mineral-laden seawater and then extract the freshwater, pumping the excess salt out of their salt glands. This often makes it look like they are crying when they are on land, because the glands are located near the eyes

  • Oviparous, meaning they lay eggs. In fact, they lay many, many eggs. For some species, a clutch (number of eggs laid per nesting attempt) can be as many as 200 eggs, and they can nest up to 9 times per season.

 

 

Below is an illustration of the anatomy of sea turtles, taken from Sea Turtles: An Ecological Guide, by David Gulko and Karen Eckert

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Species of Sea Turtles

 

Diets

Most species of sea turtle are specially adapted to feed on a type of aquatic plant or creature. Their diets influence the shape of their respective mouths and jaws, for example, the bird-like beak of the Hawksbill or the strong, blunt jaw of the Loggerhead; it also influences other parts of the alimentary canal, for example, Leatherbacks have spines in their mouth and all along their throat, and Greens have active flora (bacteria) in their gut.

  • Seaweeds and seagrasses - Green

  • Sponges- Hawksbill

  • Jellyfish - Leatherback

  • Crabs and other crustaceans - Loggerhead, Kemp's Ridley, Olive Ridley

  • Sea cucumbers and other soft-bodied invertebrates - Flatback

This list outlines the preferred cuisine of each species, but it is in no way exhaustive. Most species have been known to eat everything from algae and mangrove leaves to fish eggs.

 

Reproduction

Most Sea Turtle species are so long-lived that that it takes decades for them to reach reproductive maturity. When this finally happens, they mate, and then the females find their way ashore to lay their eggs. Females tend to return to the same beach where they hatched to lay, or if unavailable, a beach nearby.

Generally, she emerges at night and makes her way up the beach. Most species nest alone (solitary nesting), but certain species, namely the Kemp's and Olive Ridleys, may engage in aggregated or mass nestings, called arribadas. Once on the beach, the female selects an appropiate site, depending on factors like temperature, high water markings, moisture, sand grain size, dune patterns and vegetation. Once selected, the site is cleared and the female uses her large body to make a body pit to facilitate digging. The hind flippers are then used to excavate a nest hole. 

The female lays her clutch, refills the nest and then disguises it. She uses her front flippers to throw sand in all directions and make it harder to poachers or predators to find the nest. Her nesting complete, she returns to the ocean.

About six to ten weeks later (depending on the species), the eggs begin to hatch. The hatchlings use a specialized egg tooth (or caruncle) to break out of their eggs, then they begin the climb out of the nest. Working together, they make their way to just below the surface, where they wait until night (using the temperature of the sand as an indication). Finally, they emerge and begin the trek to the ocean. They use their spectral sensitivity to differentiate the subtle brightness of the open ocean from the relatively darker beach and orient themselves to the horizon.

Once in the sea, they can swim to safety and feed in order to grow. However, they face many threats - both human and natural - and only 1 in 1000 may survive to return to that beach to lay the next generation of eggs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Threats

  • Natural

    • Predators to eggs and hatchling like crabs, ants, lizards, seabirds, vultures, raccoons, sharks and predatory fish like catfish and jacks

    • Storms and high tides which can wash out nests or inundate them and prevent gaseous exchange

    • Erosion or loss of beach

    • Unusual temperatures - extreme hot or cold

    • Vegetative root growth into nests

    • Bacterial invasions

    • Fibropapillomas

  • Human

    • Artificial lighting on beaches disorients nesting females as well as hatchlings attempting to find their way to the ocean

    • Poaching of eggs for sale or adults for meat

    • Harvest of turtles for their shells and fatty tissue to make oil

    • Intentional or unintentional (bycatch) capture of turtles

    • Coastal alteration via sand mining, seawall construction, development and even attempts at rebuilding beaches using beach enrichment

    • Boating accidents

    • Marine debris from litter, especially plastic, can be mistaken for jellyfish and ingested, leading to the eventual starvation of the turtle

    • Improper disposal of fishing equipment - nets, hooks, lines, etc - which can entangle turtles of all ages and even lead to their drowning

    • Introduction of non-native species

    • Pollution in the form of oil spills, heavy metals, PCBs, nutrients and even heat

    • Careless tourist action

    • Global Warming, which not only affects the reefs upon which turtles depend for food but can also skew the sex ratio. The sex of hatchlings is determined by the temperature during incubation, which higher temperatures leading to females and lower leading to males. Global temperature increases have, and will continue to, affect the sex ratio of hatchlings, leading to more females than males, and threatening the continuity of the species.

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