Concern over a decline in annual loggerhead nest counts prompted a detailed analysis of the species' nesting trends since 1989. This summary updates that statistical analysis, published in a 2009 journal article, with data through 2011.
A detailed analysis of Florida's long-term loggerhead nesting data (1989-2011) revealed that following a 24 percent increase between 1989 and 1998, nest counts declined 16 percent between 1998 and 2011 (Figure 1). However, the recent trend may be stabilizing. Loggerhead sea turtle nest counts in 2011 were close to the average for the preceding five-year period. The study was part of the FWC's Index Nesting Beach Survey.
Figure 1. This trend line describing annual loggerhead nest counts was estimated by
fitting a 5-knot restricted cubic spline (RCS) curve to the total counts via negative
binomial regression. The 5-knot RCS model had the greatest support and appeared to
be the best choice from the available set. From the model, there was a 23.9%
increase in nesting from 1989 to 1998 and a decline of 16.4% between 1998 and 2011.
An overall 3.6% increase in nesting from 1989 to 2011 did not differ significantly from zero.
Hundreds of participants surveyed index beaches and counted turtle nests to collect data for this analysis. The participants hold a Florida marine turtle permit and are trained in sea turtle nest identification. Scientists at the FWC's Fish and Wildlife Research Institute coordinate the nest counts according to a rigorous protocol to ensure that they reveal unbiased trends.
In contrast to the loggerhead nesting trend, nest counts for green turtles and leatherback turtles in Florida have increased. In 2011, the number of leatherback nests on index beaches was the second-highest since the trend-monitoring program began in 1989, and green turtle nests on the same beaches set a record high. These two species nest on many of the same beaches in Florida as the loggerhead, but in smaller numbers.
Approximately 80 percent of the world's loggerhead population nests either on Florida beaches or in Oman, a country on the Arabian Peninsula. Florida accounts for more than 90 percent of U.S. loggerhead nesting.
View the article Index Nesting Beach Survey Totals (1989-2011) for more information on how FWRI collects nesting-trend data and for nesting trends of green and leatherback turtles.
Download the 2009 journal article Decreasing Annual Nest Counts in a Globally Important Loggerhead Sea Turtle Population.
Loggerheads Face Wide-Ranging Threats to Their Survival
In Florida, coastal development and high vessel traffic present challenges for sea turtle protection. Artificial lighting on nesting beaches causes hatchlings from nests to crawl inland rather than toward the water. On developed beaches, coastal armoring meant to protect buildings from erosion has eliminated nesting habitat where natural dunes once stood. Throughout the state's waters, collisions with boats are the most common identifiable cause of trauma in sea turtles that wash up dead on Florida beaches.
FWC's conservation work includes assisting the rescue and rehabilitation of sick and injured sea turtles and expanded efforts to guide coastal construction practices and commercial fishing activities. The agency also works to correct errant lighting that could lead sea turtle hatchlings to their death on developed beaches.
Additional threats to Florida's loggerheads occur far from the state's waters and beaches, throughout the Atlantic Ocean basin. During the approximately 30 years that it takes a loggerhead sea turtle to mature, it will travel widely through international waters and many national jurisdictions. Many drown in shrimp trawls; others get hooked or entangled by open-ocean longlines set to catch reef fish, sharks, tuna, and swordfish. Occasionally, mass strandings of dead or sick loggerheads occur without clear evidence of what disease, toxin, or event was responsible.
To help protect sea turtles outside Florida waters, the FWC provides nesting data to the federal agencies with management oversight beyond Florida's jurisdiction: the National Oceanic and Atmospheric Administration (NOAA) Fisheries Service and the U.S. Fish and Wildlife Service. These agencies provide funds for FWC's sea turtle research and monitoring.
Learn more about sea turtles and threats to their survival by visiting the Sea Turtles section of this Web site.
Persons with Disabilities