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In migratory marine species, demographic estimates are often generated from capture-mark-recapture (CMR) studies conducted at terrestrial breeding sites. However, when logistical difficulties limit the geographic area of these surveys, demographic estimates are vulnerable to biases. We compared demographic rates generated from CMR data of nesting loggerhead turtles (Caretta caretta) collected between 2010 and 2017 at one focal site (Wassaw Island, Georgia, USA; 31.89° N, 80.97° W) with estimates generated from the same group of turtles but including all other nesting events from adjacent sites in Georgia, South Carolina, and North Carolina. We found that estimates of annual recruitment at the focal site were overestimated: each year, 29–45% putative first-time nesters at the focal beach had, in fact, nested on a different beach in a previous season. Estimates of clutch frequency and breeding frequency generated at the focal site were biased low and skewed towards values of one, while estimates for remigration interval were not significantly over- or underestimated. Additionally, estimates of annual and total population productivity in terms of clutches, eggs, and hatchlings were underestimated by more than half at the focal site. Our results show how weak fidelity to a focal nesting/tagging site can affect demographic estimates in marine turtle populations and highlight the need to reconsider estimates from other populations that might be vulnerable to similar biases.

Nesting beach management is a vital element of the population recovery efforts for the vulnerable loggerhead sea turtle (Caretta caretta) across the globe. In the southeast United Sates, turtle nests are threatened by numerous anthropogenic and natural threats, including predation of eggs by native and non-native predators. We analyzed loggerhead nest predation and other egg; loss using an exceptional 10-year data set (2009–2018) that covered nesting beaches on 12 islands on the Georgia coast. Our objectives were to 1) determine which predators cause the greatest loss of loggerhead sea turtle eggs, 2) evaluate whether non-native species have a higher; rate of predation than native species, and 3) compare predation rates to other major sources of egg loss across these islands. Our results show that under current strategies for nest management: 1) non-native feral hogs and native raccoons have the greatest impact as predators on sea turtle eggs; 2) non-native predators have caused significantly more egg loss across Georgia’s coast than native species, but the impact varies greatly by species; and 3) losses to predation are similar in magnitude to post-management losses from tides and storms over the last decade. We recommend the continued use of multiple management techniques, including nest screening and; targeted predator management, but caution that predator controls should be focused on those demonstrated to cause significant losses in order to prioritize conservation funding.

Nest counts are often used as indices for nesting female abundance in marine turtle monitoring, but accurately interpreting nest count trends requires context on the scale of demographic connectivity and estimates of reproductive parameters. Weak nest site fidelity (NSF) relative to the scale of tagging effort may bias parameter estimates. The reproductive ecology of Northern Recovery Unit (NRU) loggerhead turtles (Caretta caretta) was assessed through subpopulation-scale genetic capture-recapture via clutch sampling from approximately 1000 km of coastline from Georgia to Maryland, USA (30.75–38.06°N and 75.24–81.45°W). Of 20,682 clutches recorded from 2010 to 2012, 20,222 sampled clutches were assigned to 5684 unique females through microsatellite genotyping. Approximately 73% of females detected laying multiple clutches deposited them within a 20-km span, suggesting the possibility of demographic structuring across NRU rookeries that warrants further investigation. Estimated clutch frequencies (ECF) generated from open robust design modeling were 4.28 (4.02–4.54) in 2010, 4.63 (4.45–4.80) in 2011, and 4.57 (4.28–4.77) in 2012, and were significantly higher than observed clutch frequencies. ECF generated from single-island data were biased low by 23–50% relative to those from regional genetic tagging. Among females that nested at least once on a physical tagging beach, 54% also nested elsewhere, with 81% of these “permanently” emigrating during the nesting season. This pattern of relatively strong NSF, but distributed across multiple nearby islands, confounded modeling of detection in single-island datasets and highlights the need for regional coverage for generating robust estimates of demographic parameters for marine turtles.

Recovery of loggerhead turtle Caretta caretta populations depends on many factors, including reducing anthropogenic mortality of adult turtles. Shrimp trawls are considered a major source of mortality for adult loggerhead turtles despite the mandatory use of turtle excluder devices. We modeled scenarios for reducing the likelihood of interaction between nesting adult loggerhead turtles and shrimp trawlers operating off the coast of Georgia during the nesting season (May–August). We used satellite telemetry and aerial surveys to describe the distribution patterns of nesting adult female turtles (2004–2005; n = 22) and shrimp trawls (1999–2005), respectively, across waters adjacent to the Georgia shoreline. Adult female turtles and shrimp trawlers both occupied state waters extensively during the nesting season. Turtles tended to have long, narrow home ranges that were located parallel to shore and that overlapped with the shrimp trawl distribution, which showed a slight grouping around deep channe...

The southeastern United States supports one of two large loggerhead turtle (Caretta caretta) nesting aggregations worldwide and is therefore critical to global conservation and recovery efforts for the species. Previous studies have established the presence of four demographically distinct nesting populations (management units) corresponding to beaches from (1) North Carolina through northeastern Florida, (2) peninsular Florida, (3) the Dry Tortugas, and (4) northwest Florida. Temporal and geographic genetic structure of the nesting aggregation was examined utilizing partial mitochondrial control region haplotype frequencies from 834 samples collected over the 2002 through 2008 nesting seasons from 19 beaches as well as previously published haplotype data. Most rookeries did not exhibit interannual genetic variation. However, the interannual variation detected did significantly impact the interpretation of spatial genetic structure in northeastern Florida. Based on pairwise F ST comparisons, exact tests of population differentiation, and analysis of molecular variance, the present study upholds the distinctiveness of the four currently recognized management units and further supports recognition of discrete central eastern, southern (southeastern and southwestern), and central western Florida management units. Further subdivision may be warranted, but more intensive genetic sampling is required. In addition, tools such as telemetry and mark-recapture are needed to complement genetic data and overcome limitations of genetic markers in resolving loggerhead turtle rookery connectivity in the southeastern USA.

Tagging studies on nesting beaches are commonly used to estimate nesting frequency, remigration interval and nesting population size for marine turtle rookeries. Estimates of these demographic parameters from tagging projects may be biased because of the small scale of tagging efforts relative to female nest site fidelity and the logistical difficulty of intercepting all nesting females. Therefore, alternative and supplemental means of individual identification of nesting females are required. We demonstrate that maternal nuclear microsatellite DNA can be isolated from unincubated eggshells of the loggerhead sea turtle (Caretta caretta) through comparison of DNA extracted from 59 eggs collected within 15 h of oviposition and DNA derived from skin samples from respective nesting females. Scorable microsatellite genotypes were produced in 897 of 994 (90.2%) single-locus egg amplifications attempted. Among eggs from known females, 730 of 748 (97.6%) single-locus, egg-derived genotypes matched the respective skin-derived genotypes. Allelic dropout was the most common type of error, followed by the presence of nonmaternal, presumably paternal, alleles. Genotypes derived from unincubated eggshells permit individual assignment of nests and therefore demographic parameter estimates for loggerhead turtle nesting populations, despite genotyping errors that require further optimization. Although sampling unincubated eggs is destructive, this technique is noninvasive to nesting females and is applicable in marine turtle population genetics studies when individual resolution is required but direct interception of nesting females is undesirable or logistically infeasible.

The loggerhead sea turtle (Caretta caretta) is a federally threatened species and listed as endangered by the World Conservation Union (IUCN). We describe primers and polymerase chain reaction (PCR) conditions to amplify 11 novel tetranucleotide microsatellite loci from the loggerhead sea turtle. We tested primers using samples from 22 females that nested at Melbourne Beach, Florida (USA). Primer pairs yielded an average of 11.2 alleles per locus (range of 4–24), an average observed heterozygosity of 0.83 (range 0.59–0.96), and an average polymorphic information content of 0.80 (range 0.62–0.94). We also demonstrate the utility of these primers, in addition to primers for 15 loci previously described, for amplifying microsatellite loci in four additional species representing the two extant marine turtle families: olive ridley (Lepidochelys olivacea), hawksbill (Eretmochelys imbricata), green turtle (Chelonia mydas), and leatherback (Dermochelys coriacea).

We describe primers and polymerase chain reaction conditions to amplify 15 tetranucleotide microsatellite loci from the loggerhead sea turtle ( Caretta caretta ). The primers were tested on 30 individuals that nested along the Georgia, USA coast. The primer pairs developed in this study yielded an average of 13.9 alleles per locus (range of 10–21), an average observed heterozygosity of 0.91 (range 0.79–1.00), and an average polymorphic information content of 0.88 (range 0.84–0.92).

The ''landscape of fear'' model has been proposed as a unifying concept in ecology, describing, in part, how animals behave and move about in their environment. The basic model predicts that as an animal's landscape changes from low to high risk of predation, prey species will alter their behavior to risk avoidance. However, studies investigating and evaluating the landscape of fear model across large spatial scales (tens to hundreds of thousands of square kilometers) in dynamic, open, aquatic systems involving apex predators and highly mobile prey are lacking. To address this knowledge gap, we investigated predator- prey relationships between tiger sharks (Galeocerdo cuvier) and loggerhead turtles (Caretta caretta) in the North Atlantic Ocean. This included the use of satellite tracking to examine shark and turtle distributions as well as their surfacing behaviors under varying levels of home range overlap. Our findings revealed patterns that deviated from our a priori predictions based on the landscape of fear model. Specifically, turtles did not alter their surfacing behaviors to risk avoidance when overlap in shark-turtle core home range was high. However, in areas of high overlap with turtles, sharks exhibited modified surfacing behaviors that may enhance predation opportunity. We suggest that turtles may be an important factor in determining shark distribution, whereas for turtles, other life history trade-offs may play a larger role in defining their habitat use. We propose that these findings are a result of both biotic and physically driven factors that independently or synergistically affect predator-prey interac- tions in this system. These results have implications for evolutionary biology, community ecology, and wildlife conservation. Further, given the difficulty in studying highly migratory marine species, our approach and conclusions may be applied to the study of other predator- prey systems.

Capture–mark–recapture (CMR) studies on marine turtle nesting beaches provide data on reproductive periodicity that inform population trends and models. Annual survival is estimated from observations of remigration, the return of females in subsequent nesting seasons. However, a significant proportion of tagged females are never encountered remigrating in many studies, presumably due to weak nest site fidelity (NSF). We employed a genetic CMR approach based on subpopulation-scale clutch sampling to conduct a 5-year evaluation of inter-seasonal recapture rates and NSF for Northern Recovery Unit loggerhead turtles (Caretta caretta). Of 1770 females genetically tagged from Georgia through Maryland in 2010, 1156 (65%) remigrated between 2011 and 2015. Inter-seasonal NSF, measured as shifts in median latitude nesting locations between years, was highly variable among individuals but strong overall (mean: 15.08 (± 44.61) km, median: 1.84 km). Among three focal beaches with nocturnal tagging projects, 69 of 173 females (40%) remigrated onsite whereas 115 (66%) were detected overall. Regional genetic sampling therefore yielded significantly higher inter-seasonal recapture rates, which may improve precision in future survival analyses. However, despite sampling ~ 1000 km with high annual detection probabilities (p* ≥ 0.94), 35% of 2010-females were not detected remigrating. Several non-exclusive hypotheses to explain these remaining “missing” remigrants should be considered: longer remigration intervals, imperfect detection within the study area, emigration to Florida, anthropogenic mortality, and natural mortality or senescence. This genetic tagging approach can be applied over large spatial scales where nesting densities permit, better characterizing inter-seasonal dispersal.