Sea Turtles

What is defined as a turtle? » Top

Turtles are reptiles. There are three major taxonomic "orders":

  • Order Crocodylia (alligators and crocodiles, 23 species).
  • Order Testudines (turtles, 285 species).
  • Order Squamata (lizards and snakes, 7200 species).
  • As vertebrate animals all reptiles have backbone.
  • Turtle ribs are outside of the girdles of the limbs and do not hinder movement of the legs. The ten dorsal vertebrae are expanded and fused with the carapace.
  • There aren't any sternal ribs or sternum.
  • Reptiles are primarily ectothermic, menaning that are cold blooded (ectothermic).
  • Their body temperature is the same as their surroundings.
  • Reptiles breathe air.
  • They have internal fertilization, most reptiles are oviparous, laying eggs externally in which their offspring develop. (Gulko and Eckert, 2004.)

What is defined as a sea turtle? » Top

  • Turtles first appeared on land more than 200 millions years ago. The oldest sea turtle fossil is Santanachelys, dating back some 112 millions years ago to the middle cretaceous period.
  • Sea turtles are reptiles that lived in the oceans and seas all over the world and they return to the beach to lay there eggs.
  • Sea turtle limbs have evolved into flippers and their body shape is streamlined (aquadynamic).
  • Relatively large size.
  • Elongate flipper-like forefeet used for swimming long distances, and out-maneuvering predators.
  • Hindfeet used primarily as a rudder (and for digging nests) (Gulko and Eckert, 2004.)

How large can a sea turtle get? » Top

A turtle's growth rate is determined by the temperature of its body and amount and frequency of food availability.

Some sea turtles are herbivores while others are carnivores. The giant leatherback feeds primarily on jellyfish and the hawksbill prefers sponges.

How do sea turtles reproduce? » Top

Sea turtles typically mate at sea a few weeks prior to nesting and only the females come ashore to nest, male sea turtles virtually never come ashore. Sea turtle females excavate a body pit and then begin digging the next cavity, using alternating scoops of their hind flippers. Depending on the species and size of the female, they then deposit 50-180 leathery-shelled eggs.

These eggs will typically incubate from 48 to 62 days, depending on nesting beach temperatures. The eggs are close packed and in contact with one another. Metabolic heating within the nest helps to speed up the hatching process in the final stages of incubation.

What are the stages of the nesting process? » Top

There are eleven stages in the nesting process:

  • The turtle arrive to the beaches, inspects the site where she has landed and crosses the shoreline.
  • She chooses a route and then moves slowly up the beach.
  • She chooses a place to nest.
  • She cleans the nesting site and constructs false nests.
  • She digs the body pit.
  • She digs the nest hole.
  • She lays her eggs.
  • She covers the eggs, packs down the sand and refills the nest.
  • She refills the body pit, camoflauges the nest and constructs false nests.
  • She selects a route back to the sea.
  • She returns to the shoreline and enters the sea.

How do sea turtles know in which beach to lay their eggs on? » Top

For many years sea turtle biologists have stated that female sea turtles return to their natal beach to lay their own clutches of eggs.

This ability to return to their own hatch site is called imprinting. In recent years, genetic research has proven this hypothesis to be true. Individual turtle populations are genetically distinct.

How is the hatchling process? » Top

Sea turtle hatchlings usually emerge from their underground sandy nests under the cover of darkness.

Then, when a majority of hatchlings are on the surface, they make a synchronized frenzied rush to the awaiting surf through a gamut of predators include: ghost crabs, raccoons, coyotes and feral dogs.

Scientists have demonstrated that hatchling turtles crawl toward the horizon and that they are able to detect subtle differences in light intensity.

Artificial light sources like automobiles or street lights close to hatchling beaches tend to disorient the babies and many die as they crawl away from the ocean and onto roads and highways.

Once the baby turtles enter the water, they swim aggressively toward the origin of the waves, surfacing approximately every two minutes to breathe.

Where do juvenile sea turtles go? » Top

Regardless of the species of sea turtles, no one knows where the young spend the first year of their lives, or "the lost year."

Many biologists speculate that they float in and among rafts of sargassum weed, feeding on the rich variety of small creatures that seek refuge in it.

Only a small percentage of baby turtles will survive to become adult animals and make their homeward journey to perpetuate their kind.