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Sea Turtles of Mexico

Catherine Krantz

Sea Turtles are air breathing marine reptiles that have existed in our oceans for over 150 million years, since the age of the dinosaurs. It has only been in the last 100 years that their numbers have plunged. Of the estimated 100s of sea turtle species that once lived, only eight remain. Of the world's eight remaining sea turtle species, seven are found in the waters around Mexico. Because of this dramatic loss of species diversification, all species of sea turtles are protected. Most are threatened or endangered and one species, the Kemp's ridley, that nests almost exclusively in the Gulf of Mexico (Florida, Texas and Mexico's coasts) is at the very brink of extinction.

Here on the Pacific Coast we see the migration and nesting of three species, the Green, Olive ridley and Leatherback Sea Turtles. All three of these species nest right here in Zihuatanejo Bay and the surrounding beaches.

Nesting seasons vary with the species but are usually in the summer months with the most sightings in Zihua being between June and October and lasting in less frequency until December or January.

Sea Turtles, do not have teeth but modified beaks and there is a wide variance on what they eat, depending on the species. Green and Black turtles are the only species to be strictly herbivores, once they reach adulthood they live mainly on sea grass and algae. Olive ridley's are carnivores with powerful jaws that allow them to eat clams, mussels, shrimp, fish and jelly fish. Leatherbacks have delicate jaws that restrict their diet to soft bodied animals, they live almost exclusively on jelly fish. One of the main problems faced by jelly fish eating sea turtles is the over abundance of plastic bags floating in our oceans, especially in near coastal regions. They greatly resemble jelly fish and swallowing plastic bags is a large cause of death to mature sea turtles.

Sea Turtle anatomy is perfectly suited to life in the ocean. They hear well at low frequencies underwater through eardrums covered by skin. They have poor vision out of water but underwater their vision is greatly improved and their sense of smell is excellent. With their large flippers and streamlined bodies they are strong swimmers but are awkward out of water. The females are the only ones who nest, the males never return to land after their first scramble toward the sea at birth.

The female sea turtle migrates back to the very beach she was born on to lay her eggs, sometimes covering thousands of miles and returning to the exact same spot each time she nests, sometimes within a 100 yards of her previous nest. Incubation takes between 40 and 60 days with the baby, barely palm-sized, turtles heading straight for the water after hatching. Little is known about the day to day activities of such small turtles and not much more is known about the adults. With strong currents in the open ocean to contend with and only modest vision, how sea turtles regularly manage to cover thousands of miles each year to return to the beach they were born on, is still one of the great mysteries of science. Researchers have theorized that they are able to detect both the angle and intensity of the earth's magnetic field enabling them to determine a near latitude and longitude precision. Early experiments prove sea turtles can detect magnetic fields but whether they use this for navigation has yet to be proven. Tagging efforts and satellite tracking devices have answered some of these questions but much remains to be learned from one of the earth's oldest living creatures.

Local environmental group, Viva la Bahia, has been working with the sea turtles as well as other local issues of ecological concern for almost 5 years. This year is the first year the city of Zihuatanejo has set up an official municipal program for the protection of marine turtles. Working in collaboration with Ixtapa and Zihuatanejo beach hotels, the city program has set up beach patrols that are collecting eggs from nests on unprotected beaches and taking them to protected areas for nesting and release. The program has already been a great success, their first goal of collecting 30,000 turtle eggs was quickly surpassed. In the months of July, August and September 52,500 eggs were collected from the beaches surrounding Zihuatanejo and Ixtapa. On La Ropa Beach, Hotel Villa del Sol and Hotel Paraiso Real have long been supporters of sea turtle release and have kept protected nests on their property. For more information about sea turtles and the release efforts in this area you can talk to Juan Barnard of Hotel Paraiso Real, a Marine Biologist who has been working with sea turtles for some time or Wibke Langhorst of Hotel Villa del Sol, longtime environmentalist with Viva Bahia. A great source of information about all species of sea turtles and international conservation efforts is the web site of the Caribbean Sea Turtle Conservation organization: www.cccturtle.org

October 2000

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