Sea Turtles

Sea turtles are among the oldest creatures on earth and have remained essentially unchanged for 110 million years. However, they face an uncertain future due to threats of many kinds.

Biology of Sea Turtles

Scientific Classification

Class - Reptilia

1. Reptiles are a class of cold-blooded vertebrates - their body temperature varies with their environment. Reptiles include snakes, lizards, crocodiles, and turtles.
2. Reptiles have scaly skin, breathe air with lungs, and have a three-chambered heart.
3. Most reptiles lay eggs, although some produce eggs that hatch internally.

Order - Testudines

This order includes all turtles and tortoises. It is divided into three suborders: Pleurodira (side-necked turtles), Cryptodira (freshwater turtles, snapping turtles, tortoises, soft-shelled turtles, and sea turtles), and Amphichelydia (a suborder of turtles that is now extinct).


Most scientists recognize two families of sea turtles:

Family Cheloniidae includes all sea turtles with scutes (horny plates) covering their shells.

Family Dermochelyidae are scuteless turtles with only one modern species; the leatherback turtle. A leatherback turtle is covered with leathery skin. It is the only marine turtle whose backbone is not attached to the inside of its shell.

Genus, Species

Most scientists recognize seven species and one subspecies of sea turtles:

  1. Green
    Chelonia mydas
  2. Loggehead
    Caretta caretta
  3. Hawksbill
    Eretmochelys imbricata
  4. Olive-Ridley
    Lepidochelys olivacea
  5. Flatback
    Natator depressus
  6. Leatherback
    Dermochelys coriacea


Sea turtles are air-breathing reptiles remarkably suited to life in the sea. Their hydrodynamic shape, large size, and powerful front flippers allow them to dive to great depths and swim long distances. After their first frantic crawl from the nest to the ocean, male sea turtles never return to the shore again, and females come back only long enough to lay eggs.

Sea turtles have long and narrow wing-like flippers in place of forelimbs and have shorter flippers as hind limbs; unlike their terrestrial relatives, they cannot retract their heads into their shells.

In most sea turtles, the top shell, or "carapace", is composed of many bones covered with horny scales or "scutes." Turtles are toothless but have powerful jaws to crush, bite, and tear their food.

The smallest of the sea turtles are the ridleys, weighing in at 85 to 100 pounds as adults. Leatherbacks are the behemoths and can grow to 2,000 pounds. Most sea turtles grow slowly and have a life-span of many decades. Although sea turtles can remain submerged for hours at a time while resting or sleeping, they typically surface several times each hour to breathe.


Newly hatched sea turtles inhabit a much different environment than adult turtles. After emerging from the nest, hatchlings enter the water and must swim quickly to escape near shore predators. There is strong evidence that many sea turtle species employ an open ocean developmental stage because encounters with healthy, neonate sea turtles are extremely rare in near shore waters.

Juveniles of many species of sea turtles have been known to associate with floating sargassum seaweed, utilizing the sargassum as an area of refuge, rest, and/or food. This developmental drifting period is hypothesized to last about two years or until the turtle reaches a carapace length of about 8 inches (20 cm).
Subsequently, these sub-adult turtles return to neritic zones of the Gulf of Mexico or northwestern Atlantic Ocean to feed and develop until they reach adulthood.


Mating occurs roughly every 2 to 3 years in shallow waters. In summer, an ancient reproductive ritual begins when the female leaves the sea and crawls ashore to dig a nest in the sand. She uses her rear flippers to dig the nest hole and then she deposits 80 - 150 eggs that look a lot like ping-pong balls.

When egg-laying is complete, the turtle covers the eggs, camouflages the nest site, and returns to the ocean. Nesting turtles may come to shore several times in a nesting season to repeat the process.

As is true for some other reptiles, the temperature of the sea turtle nest determines the sex of the hatchlings. Warmer temperatures produce more females, whereas cooler temperatures result in more males. Consequently, conservationists and wildlife managers leave turtle eggs in their original location whenever possible so that sex ratios are determined naturally.

After incubating for about two months, the eggs begin to hatch. Hatchlings range from 1.5 - 3 inches in size, depending on the species, and emerge from the nest as a group. This mass exodus usually occurs at night, and the hatchlings use the bright, open view of the night sky over the water to find their way to the sea. Artificial lights on beachfront buildings and roadways can distract hatchlings on their way to the ocean. Because of this danger, many beachfront communities in Florida have adopted lighting ordinances requiring lights to be shut off or shielded during the nesting and hatching season.