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 The goal of the Bermuda Turtle Project is, "to promote the conservation of marine turtles through research and education". The project team has made notable progress to date and has exciting plans for expanding research and education objectives.
The Bermuda Turtle Project has assembled important data sets on growth rates, sex ratios, site fidelity, genetic diversity and movement patterns in immature green turtles.
Our findings show that Bermuda serves as a year-round habitat for immature green and hawksbills turtles, providing a 'developmental' feeding ground for Caribbean animals.
Our data show that green turtles arrive at Bermuda at a size of about 25 centimeters (10 inches) and leave by the time they have grown to approximately 75 centimeters (30 inches) - size distribution graph (88k). Stranding records show a similar distribution of sizes.
Green turtles are about the size of a silver dollar when they are born, and take about thirty to fifty years to reach carapace lengths over 1 meter (3.28 feet) and weights in excess of 150 kilograms (330 pounds). Thus, it is easy to see how a project such as ours, which has been gathering data since 1968, is so valuable. It takes years to collect enough data to understand life history patterns.
The gaps at either end of the size distribution of green turtles in Bermuda are consequences of the pelagic phase that follows hatching, known as the 'lost year,' and the departure of large, but still immature, sub-adults to the adult resident habitat.
 During the years 1990 through 1992, most turtles captured by the project were laparoscoped. In this procedure, a small incision is made through the body wall of the turtle and the gonads are viewed using a surgical scope to determine sex and maturity status. By examining one hundred and thirty eight immature turtles, we were able to calibrate a hormone assay that allows us to determine a turtle's sex from a blood sample.
Caldwell and Mowbray in 1954 wrote that greens in Bermuda were probably itinerant and were delivered to the island annually by the Gulf Stream. By modifying project sampling to include year round field trips, we have discovered that green turtles are year round residents. We actually found a population density in January matching, if not surpassing, that of the summer months. This is possible because Bermuda waters do not drop in temperature more than ten degrees Fahrenheit each winter. Bermuda waters stay as warm as those of the SE coast of Florida.
Information from local recaptures has shown that young green turtles in Bermuda establish specific feeding areas. Even if displaced, they usually return to these particular sites and may stay there for many years.
The greatest number of times that a single individual turtle has been captured is seven. This turtle was captured on the same grass flat each time and may still reside there. The longest period of time over which we know an individual has remained in Bermuda waters is fourteen years. This turtle was probably in Bermuda for six to seven years before initial capture and will probably be here for another six to seven years before departing, having a total probable residency time of twenty to twenty-five years. This turtle switched from a flat used mostly by smaller immatures to one with large immatures about five miles away.
Using a Geographic Information System (GIS) we can visualize patterns of habitat use that may be related to seasonality, turtle size, turtle sex, and other biological and physical characteristics of the habitat. Analysis of turtle distribution data with GIS will be of great benefit to management authorities in identifying critical habitat.
 Blood samples are taken from each turtle to determine sex and genetic identity. Blood samples taken for sex determination are centrifuged and the serum is frozen. Later, these samples are sent to Dr. Dave Owen's lab at the Grice Marine Laboratory, College of Charleston, SC, where the amount of testosterone in the blood is determined. These data can be used to determine the sex of immatures. A second blood sample is transferred into buffer which preserves DNA for genetic analysis.
During 1996, we compiled and analyzed genetic sequence data from Bermuda turtles. Our studies show that Bermuda turtles match gene sequences of known green turtle populations from Florida, Mexico, Costa Rica, Aves Island near Dominica, Suriname and a population that nests at several sites in the South Atlantic.
To date, 72 green turtles caught and tagged in Bermuda have been found overseas in Venezuela, Colombia, Nicaragua, Panama, Cuba, the Dominican Republic, Saint Lucia, the U.S. and Grenada - map of tag returns (36K). This information, along with genetic results, highlights the regional importance of Bermuda to the green turtle. It also confirms the need for international cooperation in their conservation. Unless they are protected on the nesting beaches and in their adult ranges, Bermuda may lose the green turtle, in spite of efforts to protect them in our waters. To date, the project has recorded only one international recapture of a hawksbill turtle. The animal was captured with a spear gun off the east coast of Grenada eleven years after being tagged in Bermuda.
In 1996, our first satellite transmitter was attached to a Bermuda turtle. The transmitter emits a signal when the turtle surfaces to breathe, and data (latitude, longitude, location accuracy, dive frequency and duration, and temperature) are uploaded to an ARGOS satellite, if it is overhead. Positions of the turtle are plotted using the Geographic Information System developed for the project. The first transmitter sent data for fifteen months. Most positions recorded were centered on the capture area, and it is believed that the turtle did not travel any significant distance.
In August 1998, three additional satellite transmitters were attached to turtles that were approaching the size at which they leave Bermuda. One of the turtles departed the Bermuda platform about two weeks later, and we were able to record her remarkable journey of approximately 1,500 kilometers (1,932 miles) which took her south to the Dominican Republic and then west to Cuba. This turtle, named "Bermudiana," was originally captured on August 5th with a net on the seagrass flats off the northwestern end of Bermuda. The animal measured 79 cm (31 inches) in shell length and weighed 68 kgs (150 lbs). Location and dive data were received for the turtle on a daily basis. The turtle was just north of the coast of the Dominican Republic as Hurricane Georges passed by, but there were no observable effects. Several days later, however, transmissions changed dramatically and eventually stopped. We believe that Bermudiana was captured off the eastern tip of Cuba, near the town of Baracoa - map of Bermudiana's movements (29K).
The team has also experimented with more traditional set nets. These nets are deployed in a linear fashion and tended from a boat. Set netting was conducted to test whether turtles larger than those caught in the entanglement net are present in Bermuda waters. Although some turtles were caught, all were of typical sizes.
The Bermuda Turtle Project serves as a useful vehicle for public outreach and education. In addition to the one hundred-plus volunteers who join the field efforts each year, teachers, school classes, and eco-tour groups are educated about the plight of the endangered green turtle through slide shows and lectures.
The Bermuda Turtle Project hosts an International Course on the Biology and Conservation of Sea Turtles each year. The two-week course consists of lectures, class discussions of assigned readings, a necropsy session, and extensive field work capturing immature green turtles. Over the eight years the course has been offered, it has served 79 students, primarily from countries and territories bordering the Caribbean Sea and western Atlantic Ocean. These include Anguilla, Belize, Bermuda, Bonaire, the British Virgin Islands, Canada, the Cayman Islands, Costa Rica, Cuba, Grenada, India, the Netherlands, Nicaragua, St. Lucia, the Turks and Caicos Islands, the U.K. and the U.S.
In 1997, four papers on the Bermuda Turtle Project were presented at the Annual Symposium on Sea Turtle Biology and Conservation. The findings of our research are presented and published locally and internationally in an effort to increase public awareness. We hope that the Caribbean nations that receive the turtles that have grown up in Bermuda will soon come to appreciate them as much as Bermudians do.
The Bermuda Turtle Project looks forward to sharing our new discoveries with you!
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