This image courtesy of SEMARNAT
Swimming green sea turtle

This image courtesy of Turtle Trax
A nesting female green sea turtle lays her eggs

Conservation Organizations

Sea Turtle Survival League-Caribbean Conservation
The organization engages in education, research and advocacy designed to protect, promote and enhance the globally important sea turtle nesting beaches of the Carr Refuge program.

ASUPMATOMA
Non-profit organization that focuses on the environment and preservation of sea turtles.

EUROTURTLE
This site connects to MEDASSET organization that works exclusively on the conservation of sea turtles throughout the Mediterranean Sea.

Inter-American Convention for the Protection and Conservation of Sea Turtles
This is the only international treaty dedicated exclusively to sea turtles, setting standards for the conservation of these endangered animals and their habitats.

This image courtesy of MIR
Mating green sea turtles

This image courtesy of MIR
Mating green sea turtles

This image courtesy of Lost Horizons Resorts
Green sea turtle hatchlings

This image courtesy of Nisbet Business Services
A green sea turtle infected with the fibropapillomas virus

Chelonia mydas

Introduction

Green sea turtles inhabit temperate and tropical waters in Central America, the Bahamas and the United States (To see a map of green turtle ranges: www.cccturtle.org/green.htm . It is rare to find a green turtle in the open ocean and they generally live in waters near the coast, near islands, or in protected bays (Caribbean Conservation Corporation, 1996) . They average 3.3 feet in length and weigh approximately 375 pounds (SeaTurtle.org, Inc., 1999). Their protective shell is made of three parts; the carapace (upper portion), the plastron (lower portion), and the scutes (scales). Green sea turtles have an excellent sense of smell, but become very nearsighted when they leave the water (Caribbean Conservation Corporation, 1996) .

Green sea turtles are strictly herbivorous sea turtles and subsist mainly on marine algae and grasses. However, when they are juveniles, they have a diet of jellyfish, sponges, snails, worms, and small mollusks (The Animal Diversity Web, 1995-2001).

The nesting season for Green sea turtles is typically in May and June and the females return to nest at their natal beach, the place where they were hatched (Caribbean Conservation Corporation, 1996). Males court females by nuzzling their head or gently biting their flippers and neck. If the female does not reject the male, he grabs on to her back and folds his tail under her shell to copulate. A female will often mate with several males so when she lays her eggs, there will be several different types of sperm available for fertilization. This increases the genetic diversity of the offspring (Biological Resources Division, 1996). Females lay eggs about once every three years and make their nests far above the high tide line. The males never leave the sea. When the females come out of the water, they dig a hole with their strong flippers that is approximately eight inches in diameter and eighteen inches deep and fill the hole with about 100 eggs. Once the female lays her eggs, she returns to the sea and never has any contact with her offspring (Biological Resources Division, 1996). The incubation period for the eggs usually lasts 50-70 days. During the incubation period, the temperature of the sand surrounding the nest determines the sex of the hatchling. If the sand is warm (above 29 degrees Celsius) the hatchlings will be female and if the sand is cooler (below 29 degrees Celsius) the hatchlings will be male (California Turtle and Tortoise Club, 1992).
After the incubation period, green sea turtle hatchlings break out of their shell using a special sharp tooth called a caruncle (World Wildlife Fund, 2001). The eggs hatch at night or on overcast days when the sand temperatures are cool. After hatching, the small green sea turtles crawl directly towards the water where they will spend most of their adult life.

Conservation Status

The 2000 IUCN Red List of Threatened Species: Listed as Endangered. The Population experienced a reduction of at least 80% over the last 10 years or three generations based on direct observation. The reasons might be due to the on the effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites. But in Mediterranean sub-population, it is listed as Critically Endangered.

CITES: All the species of Cheloniidae are listed on Appendix 1.

Conservation Issues

Though sea turtles face a number of natural predators, such as raccoons, ants and crabs while in the nest, birds and crabs as free-swimming hatchlings, and occasionally even sharks once fully grown, green sea turtles are not becoming extinct due to these natural threats. Humans play the largest role in the extinction of these ancient, endangered animals (Caribbean Conservation Corporation, 1996; World Wildlife Fund, 2001). The greatest threats green sea turtles face are harvesting of their eggs by poachers and the selling of adult sea turtle meat and turtle parts as jewelry. In many tropical countries and southern portions of the United States where green turtles nest people still harvest the eggs of sea turtles for consumption(Caribbean Conservation Corporation, 1996; World Wildlife Fund, 2001). In these same areas, the meat of adult sea turtles is sold as a delicacy. Jewelry made out of turtle parts and entire stuffed turtles are often sold to tourists around the Caribbean. These practices continue on a regular basis despite strict laws prohibiting the buying and selling of sea turtles in the U.S. and countries which contain sea turtle habitat (Caribbean Conservation Corporation,1996; National Marine Fisheries Service, 2001).

Fishing also has a great impact on the decreased survival of sea turtles. The west Atlantic coast and the Gulf of Mexico are both important habitat for turtles. Yet they are also the major shrimping grounds in the United States. While US shrimpers are now required to include Turtle Excluder Devices (TEDs) in their nets, unfortunately not all fishermen comply and thousands of sea turtles become entangled and often drown in shrimp nets every year (Caribbean Conservation Corporation, 1996; National Marine Fisheries Service, 2001). However, it is not only shrimp fishermen who are guilty of endangering sea turtles. Japanese tuna longline fisheries, hook and line fishing (which catch and harm coastal species), and pound net fisheries off the coast of Virginia, are all sources of endangerment for green sea turtles. In recreational areas where water traffic is great, sea turtles can also be injured due to collisions with ship propellers (Caribbean Conservation Corporation, 1996; National Marine Fisheries Service, 2001).

Another major reason sea turtles continue to be endangered is due to human pollution. Non-degradable trash, including balloons, bottles, vinyl films, styrofoam, twine, and especially plastic bags are deadly to turtles. They often mistake floating plastic bags to be floating jellyfish, a staple of their diet (Caribbean Conservation Corporation, 1996). The effects of oil spills, chemical runoff, and fertilizers are also extremely negative as they disrupt the respiration, blood chemistry, skin, and salt gland functions of the sea turtles (Caribbean Conservation Corporation, 1996; National Marine Fisheries Service, 2001). There is evidence now suggesting that fibropapillomas, a disease killing many sea turtles, could be connected to pollution in the oceans (Caribbean Conservation Corporation, 1996; Turtle Trax, 2001). Pollution also kills off the aquatic plant life green sea turtles rely on for nourishment (Caribbean Conservation Corporation, 1996).

Along with all of these other sources of human-induced endangering of sea turtles, are the repercussions of human development. Artificial lighting from coastal developments not only disturb females from nesting, but also disorient new hatchlings, causing them to migrate inland and have a greater chance of dying due to predation or dehydration (Caribbean Conservation Corporation, 1996; National Marine Fisheries Service, 2001). Coastal armoring, including sea walls, sandbags, and rock revetments, along with beach nourishment, an alternative to coastal armoring also meant to prevent the beach from eroding, can both seriously negatively impact sea turtles by either blocking female turtles from their nesting habitat and altering nesting habitat. If beach nourishment occurs during nesting season, it is possible for nests to be either buried too far beneath the surface for individuals to survive, or the nests can be crushed by the heavy machinery used (Caribbean Conservation Corporation, 1996; National Marine Fisheries Service, 2001). If the sediments used in nourishment is extremely different from the original beach sand, nest-site selection, incubation temperature, and the moisture content of nests can also be adversely affected (Caribbean Conservation Corporation, 1996). Also, with an increase in human use of a nesting beach, the nighttime disturbance of nesting females, the use of off-road vehicles and repeated mechanical raking of nesting beaches which cause sand compaction, and the placement of physical obstacles on beaches can create serious problems for hatchlings and nesting females alike (Caribbean Conservation Corporation, 1996; National Marine Fisheries Service, 2001).

In order to protect green sea turtles, countries will have to cooperate on an international level. Feeding and nesting grounds must be protected, the laws that are already exist to protect sea turtles must be enforced, education about wildlife conservation must become more widespread, and international agreements regarding pollution levels, fishing and coastal development levels must be created and carried out.

Literature Cited

ASUPMATOMA. 2001. Home page. http://www.mexonline.com/tortuga.htm Accessed 2001 November 7.

Biological Resources Division. 1996. Home Page. http://www.co.broward.fl.us/bri00600.htm#seaturtle Accessed 2001 November 1.

Caribbean Conservation Corporation. 1996. Home Page. http://www.cccturtle.org/contents.htm Accessed 2001 November 1.

CITES. 2001. Home Page. http://www.cites.org/eng/append/I&II_0700.shtml Accessed 2001 November 7.

Euro Turtle. 2001. Home Page. http://www.euroturtle.org/ Accessed 2001 November 7.

Forbes, Gregory A. 1992. Home Page. http://www.tortoise.org/archives/green.html Accessed 2001 October 28.

Hilton-Taylor, C. (compiler) 2000. 2000 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland and Cambridge, UK. xviii + 61pp. Downloaded on 12 November 2001. http://www.redlist.org/search/details.php?species=4615 Accessed 2001 November 7.

Lost Horizons Resorts. 2001. Home Page. http://www.losthorizonsasia.com/Conservation.html Accessed November 7.

MIR. Date unknown. Home Page. http://www.mir.com.my/potpourri/places/mpwong/living_sea/inside.htm Accessed 2001 November 7.

Nisbet Business Services. 1997 August. Home Page. http://www.coffeetimes.com/aug97.htm Accessed 2001 November 7.

SeaTurtle.org, Inc. 1999. Home Page. http://www.seaturtle.org Accessed 2001 November 2.

Semarnat. 2001. Home page. http://www.semarnat.gob.mx/especies/tortuga/verde.shtml Accessed 2001 October 29.

Turtle Trax. 2001 January 11. FP papers presented at the 19th annual sea turtle symposium. http://www.turtles.org/99fp.htm Accessed 2001 November 10.

World Wildlife Fund. 2001. Home Page. http://www.panda.org/species/turtle.cfm Accessed 2001 October 26.

Authors: Melissa Breck, Jennifer Malley, and Sangmi Choung
Creation/revision date: November 12, 2001

Earlham · Biology Department · Biology 26 : Biological Diversity