Related Experiment Video
Updated: Jun 24, 2026
13:18
Data Collection on Marine Litter Ingestion in Sea Turtles and Thresholds for Good Environmental Status
Published on: May 18, 2019
Decreasing annual nest counts in a globally important loggerhead sea turtle population
Blair Witherington1, Paul Kubilis, Beth Brost
1Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, 9700 South A1A, Melbourne Beach, Florida 32951, USA. witherington@cfl.rr.com
Summary
Loggerhead sea turtle nesting in Florida showed an initial increase followed by a significant decline between 1989 and 2006, suggesting a decrease in the adult female loggerhead population. This trend highlights conservation concerns for this species.
Area of Science:
- Marine Biology
- Conservation Science
- Ecology
Background:
- Loggerhead sea turtles (Caretta caretta) exhibit complex life stages and migratory behaviors.
- Nesting patterns are crucial indicators of population health and distribution.
- Florida beaches are significant nesting grounds for loggerhead sea turtles.
Purpose of the Study:
- To analyze spatial and temporal trends in loggerhead sea turtle nesting on Florida beaches.
- To assess changes in nest counts and densities over an 18-year period (1989-2006).
- To identify patterns and potential drivers of loggerhead nesting trends.
Main Methods:
- Utilized an 18-year time series of Index Nesting Beach Survey (Index) nest-count data.
- Employed negative binomial regression models with restricted cubic splines for trend analysis.
- Analyzed both regional nest-count totals and zone-level nest densities, incorporating spatial and temporal correlations.
Main Results:
- Loggerhead nest counts in Florida initially increased then declined, showing a net decrease over 18 years.
- Annual mean nest density significantly declined by 28% between 1989-2006, with a steeper decline of 43% from 1998-2006.
- Strong positive autocorrelation in nest distribution indicated consistent spatial patterns year-to-year.
Conclusions:
- The observed decline in loggerhead nest counts is attributed to a decrease in the adult female loggerhead population.
- Understanding these trends is vital for effective loggerhead sea turtle conservation strategies.
- Further research into the causes of population decline is warranted.
Related Concept Videos
02:07Conservation of Declining Populations
Conservation of declining population focuses on ways of detecting, diagnosing, and halting a population decline. The approach uses methods to prevent populations from going extinct.
02:04Conservation of Small Populations
Small population sizes put a species at extreme risk of extinction due to a lack of variation, and a consequent decrease in adaptability. This weakens the chances of survival under pressures such as climate change, competition from other species, or new diseases. Large populations are more likely to survive pressures such as these, as such populations are more likely to harbor individuals that have genetic variants that are adaptive under new stresses. Small populations are much less likely to...
00:57Population Growth
Population size is dynamic, increasing with birth rates and immigration, and decreasing with death rates and emigration. In ideal conditions with unlimited resources, populations can increase exponentially, which plots as a J-shaped growth rate curve of population size against time. This type of curve is characteristic of newly-introduced invasive species, or populations that have suffered catastrophic declines and are rebounding.However, realistic environmental conditions limit the number of...
01:50Threats to Biodiversity
There have been five major extinction events throughout geological history, resulting in the elimination of biodiversity, followed by a rebound of species that adapted to the new conditions. In the current geological epoch, the Holocene, there is a sixth extinction event in progress. This mass extinction has been attributed to human activities and is thus provisionally called the Anthropocene. In 2019 the human population reached 7.7 billion people and is projected to comprise 10 billion by...
02:31Habitat Fragmentation
Habitat fragmentation describes the division of a more extensive, continuous habitat into smaller, discontinuous areas. Human activities such as land conversion, as well as slower geological processes leading to changes in the physical environment, are the two leading causes of habitat fragmentation. The fragmentation process typically follows the same steps: perforation, dissection, fragmentation, shrinkage, and attrition.
01:39Keystone Species
Measures of species biodiversity, such as richness (i.e., the number of species present) and evenness (i.e., their relative abundance), describe an ecological community’s structure. Many factors affect community structure, including abiotic factors (e.g., sunlight and nutrients), disturbances (e.g., fire or flood), species interactions (e.g., predation or competition), and chance events (e.g., foreign species invasion). Certain species—such as keystone species—also play a pivotal role in the...