Index Nesting Beach Survey Totals (1989-2021)
The Florida Index Nesting Beach Survey (INBS) records sea turtle nest counts on a standardized set of index beaches. Researchers use the annual survey to determine nesting trends.
Since 1989, the Fish and Wildlife Research Institute (FWRI) has coordinated the Index Nesting Beach Survey (INBS), a detailed sea turtle nesting-trend monitoring program conducted in conjunction with the Statewide Nesting Beach Survey. The index survey uses a standardized data-collection protocol to measure seasonal nesting and allow accurate comparisons between beaches and between years. Consistent effort by location, fixed dates, and specialized annual training of beach surveyors make the index program suited to these trend assessments. Approximately 30 percent of Florida's beach length is surveyed following the index-survey protocol.
FWRI coordinates data collection through a network of surveyors, including federal, state and local park personnel; other government agency personnel; members of conservation organizations; university researchers; and private citizens. FWRI staff provides annual training to beach surveyors and compiles data from the annual surveys.
At a core set of index beaches monitored since 1989, trained surveyors monitor 330 kilometers of nesting beaches (205 miles) divided into zones that average 0.8 kilometers (approximately a half mile) in length. These core index beaches represent the Atlantic and Gulf coasts of peninsular Florida. Beach surveyors monitor core index zones daily during a 109-day sea turtle index-nesting season (May 15 through August 31). Surveyors record nests and nesting attempts by species, nest location and date. Index nest counts represent approximately 51 percent of known loggerhead nesting in Florida, 70 percent of known green turtle nesting and 31 percent of known leatherback nesting.
A loggerhead sea turtle nesting throws sand over a nest, concealing her eggs, on an index beach in Brevard County.
Photo credit FWC/FWRI taken with infrared camera to reduce disturbance to wildlife.
Observed loggerhead nest counts on Florida’s 27 core index beaches have varied greatly since the beginning of the program in 1989, reaching a minimum of 28,876 in 2007 and a maximum of 65,807 nests in 2016. In 2020 loggerhead turtles had another successful nesting season with more than 49,1000 nests documented on Florida’s 27 core index beaches bringing loggerhead nest counts to levels more commonly observed in the 1990s. These numbers DO NOT represent Florida’s total annual nest counts because they are collected only on a subset of Florida’s beaches (27 out of 224 beaches) and only during a 109-day time window (May 15 through August 31). The standardized data collection approach used by the INBS program is designed to examine nesting trends. Loggerhead nest counts on Florida’s 27 core index beaches has been increasing in recent years. However, long-term loggerhead nesting data (1989-2021) reveal a complex pattern with three distinct phases: increasing (1989-1998), decreasing (1998-2007) and increasing (2007-2021). Researchers do not yet understand fully what drives fluctuations in annual nest count. The observed pattern may even be part of a long-term cycle, but many more years of standardized nest counts are needed to assess this hypothesis.
Below: Annual loggerhead nest counts on core index beaches. Survey effort remained nearly identical. These data represent peninsular Florida and exclude an additional set of beaches in the Florida Panhandle and southwest coast that were added to the program in 1997 and in more recent years.
In 2021 loggerhead nest count on Florida Panhandle index beaches, which are not part of the set of core beaches, was below the count observed in 2020 but still comparable to nest count levels observed in the 1990s. This count does not include three additional beaches that joined the INBS program in the Panhandle in 2016: St. George Island State Park, St. Joseph Peninsula and Gulf Island National Seashore. Florida Panhandle beaches host the bulk of clutches laid by the small and genetically distinct Northern Gulf of Mexico Recovery Unit.
Fluctuations in nest count may be the result of a small change in number of females or changes in reproductive parameters. More years of standardized nest counts are needed to understand whether the fluctuation is natural or warrant concern.
Concern over declines in annual loggerhead nest counts (observed between 1999 and 2007) prompted researchers to conduct a detailed analysis of the species’ nesting trends since 1989. Download a 2009 journal article about the research:
Decreasing Annual Nest Counts in a Globally Important Loggerhead Sea Turtle Population.
An updated detailed analysis of loggerhead nesting trends for Florida’s 27 core index beaches (1989-2018) and Florida Panhandle (1997-2018) index beaches can be found in the following Open Access article by Ceriani et al. (2019):
Conservation implications of sea turtle nesting trends: elusive recovery of a globally important loggerhead population
Green Turtle Nests
Green turtle nest counts have increased eightyfold since standardized nest counts began in 1989 – a trend that differs dramatically from that of the loggerheads that nest on the same beaches. In 2021, green turtle nest counts on the 27 core index beaches reached more than 24,000 nests recorded. These numbers DO NOT represent Florida’s total annual nest counts because they are collected only on a subset of Florida’s beaches (27 out of 224 beaches) and only during a 109-day time window (15 May through 31 August). Nesting green turtles tend to follow a two-year reproductive cycle and, typically, there are wide year-to-year fluctuations in the number of nests recorded. Green turtles set record highs in 2011, 2013, 2015, 2017 and 2019. The nest count in 2021 did not set another record high but was only marginally higher than 2020, an unusually high “low year”. Changes in the typical two-year cycle have been documented in the past as well (e.g., 2010-2011) and are not reason of concern.
Below: Annual green turtle nest counts on core index beaches. Since 1989, nest counts have ranged from less than 300 to almost 41,000 in 2019. Numbers show a mostly biennial pattern of fluctuation, with records set on 2011, 2013, 2015, 2017 and 2019.
Surveyors counted 435 leatherback nests on the 27 core index beaches in 2021. Leatherback nest count was slightly lower compared to the numbers of nests documented during the 2009-2015 period. These counts do not include leatherback nesting at the beginning of the season (before May 15), nor do they represent all the beaches in Florida where leatherbacks nest; however, the index provided by these counts remains a representative reflection of trends. Like nest counts for green turtles, leatherback nest counts have been increasing exponentially over the period of monitoring. However, while green turtle nest numbers on Florida’s index beaches continue to rise, leatherback nest numbers reached a peak in 2014 followed by a steep decline (2015-2017) and a promising increase (2018-2021). Florida hosts only a few hundred nests annually and leatherbacks can lay as many as 11 clutches during a nesting season. Thus, fluctuations in nest count may be the result of a small change in number of females. More years of standardized nest counts are needed to understand whether the fluctuation is natural or warrant concern.
Below: Annual leatherback nest counts on core index beaches. From 1989 through 2021, leatherback nests at core index beaches varied from a minimum of 30 nests in 1990 to a maximum of 657 in 2014.