Explanation of Indicator
Sea turtles are air-breathing reptiles remarkably adapted to life in the sea. Their streamline shape, large size, and powerful foreflippers allow them to dive to great depths and travel long distances. Although completely adapted to the ocean, sea turtl
es are tied to the land because of their nesting activity. Much of the research on sea turtles has focused on nesting females and hatchlings because these are the easiest to find and study. Thousands of sea turtles have been tagged to collect informatio
n about their reproductive cycle. More recently, satellite tracking has
been utilized to gather information about other phases of the sea turtles’
lives.1
More than in any state in the nation, the sea turtle fauna of Florida is the most diverse and abundant. There are three species of sea turtles that regularly nest on Florida’s extensive coast: loggerhead, Caretta caretta; green turtle, Chelonia mydas; and leatherback, Dermochelys cariacea. Two other species, the hawksbill, Eretmochelys imbricata, and Kemp’s ridley, Lepidochelys kempii, inhabit Florida’s coastal waters, bays, and lagoons. The loggerhead population that nests in the southeastern United States (primarily in Florida) is the second largest in the world and accounts for 35 to 40 percent of loggerhead nesting worldwide.2 Florida’s east coast from New Smyrna Beach south to Boca Raton accounts for approximately 80 percent of the nesting activ ity on the east coast of the United States.3 Florida’s green turtle nesting population is one of the largest remaining in the Caribbean Sea and western Atlantic Ocean. The only site in the continental United States where the leatherback turtle regularly nests is Florida. All of the marine turtles that nest on Florida’s beaches are protected under the Florida Statutes (Chapter 370.12).4
Data on the number of nests and survey effort are presented. Survey effort is defined as the number of kilometers of beach that were monitored for nesting activity each year for a particular species.
Data Characteristics
SOURCE
This information can be found in the report, Sea Turtle Nesting Activity
in the State of Florida, 1979-1992. To obtain a copy of the report or
additional information, contact Anne Meylan, Florida Marine Research Institute, Florida Department of Environme
ntal Protection, 100 Eighth Avenue, S.E., St. Petersburg, Florida 33701-5095, or at (813) 896-8626, extension 220.
ACQUISITION
Data can be obtained in hard copy format at no cost.
COLLECTION
The data are primarily obtained from early-morning surveys of tracks on beaches that are used as nesting sites by sea turtles. In some cases, observers were present during the night and actually witnessed nesting activities. Species identification and t
he assessment of nesting success were usually based on a surveyor’s evaluation of features of the track and nest (e.g., track width, track configuration, size of the body pit).
Data Limitations
The statewide nesting database reflects heterogeneous data collection efforts and varying levels of surveyor experience. It also covers a fourteen year period, during which methodologies and survey efforts changed significantly (e.g., survey effort incre
ased several-fold during this time period). The surveys are targeted primarily toward the loggerhead turtles and therefore, because of differences in nesting seasons of different species, do not encompass the entire nesting seasons of the green turtle an
d leatherback. As a result, the total number of nests for these two species are underestimated. Furthermore, errors in species identification do occur, principally because of deterioration of the tracks and surveyor inexperience; however, there is no re
ason to believe that these errors would significantly alter the results of the surveys.
Because of these limitations, the data must be interpreted cautiously and appropriately. Although the information may be useful in evaluating the relative importance of a particular beach or county as a site for sea turtle reproduction, the data may not be completely appropriate for evaluating long-term trends in nesting population.
Data Analysis
Nesting activity (defined here as the numbers of nests counted) of all three species of sea turtles experienced an overall increase from 1979 to 1994. During this time period, the survey effort (i.e., the number of kilometers of beach that were monitored
for nesting activity each year for a particular species) also experienced an overall increase. Nesting activity for the loggerhead increased 609 percent from 1979 to 1994; the survey effort increased 429 percent for this time period. Nesting activity f
or the green turtle increased 6,024 percent while the survey effort increased only 417 percent. Nesting activity for the leatherback increased 1,339 percent from 1979 to 1994 and survey effort increased 108 percent.
In addition to increased survey effort, another factor that may contribute to the overall increase in nesting population is the ongoing protection efforts focused on these species.
Loggerhead Green Turtle Leatherback Year Number of Survey Number of Survey Number of Survey Nests Effort (km) Nests Effort (km) Nests Effort (km) 1979 10,121 222.4 62 132.2 18 132.2 1980 12,460 311.0 331 225.9 10 225.9 1981 13,827 361.0 89 202.6 42 202.6 1982 20,889 336.2 243 173.5 45 173.5 1983 23,039 441.8 281 194.2 39 194.2 1984 21,695 450.6 181 249.6 41 249.6 1985 27,017 562.5 737 274.3 89 274.3 1986 33,115 628.4 313 247.4 41 247.4 1987 32,942 749.1 800 349.6 117 349.6 1988 37,242 940.7 455 354.7 106 354.7 1989 49,422 972.0 579 392.4 98 392.4 1990 66,685 1004.6 2,266 398.8 120 398.8 1991 68,614 1060.0 554 396.9 188 396.9 1992 64,974 1090.8 2,509 407.1 177 407.1 1993 55,813 1102.8 435 387.0 142 348.9 1994 71,756 1175.6 3,797 683.4 259 275.3
