Data from: Sea turtle nesting beach fidelity revealed by satellite tracking
Data files
Sep 09, 2026 version files 20.86 KB
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Data_Beach_fidelity.zip
15.20 KB
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README.md
5.66 KB
Abstract
Site fidelity describes the tendency to return to or reuse familiar sites, yet some animals may use alternative sites while maintaining fidelity to primary locations, with consequences for population estimates as well as resilience to changing environments. Here we assessed and compared nesting beach fidelity of hawksbill turtles (Eretmochelys imbricata) on Frégate Island, Seychelles using data from beach foot patrols (2017-2025; n = 575 turtles) and satellite telemetry (2023; n = 10 turtles) and then examined the implications of fidelity strategies for population estimates. We also reviewed published literature on nesting beach use across sea turtle species. Satellite tracking showed that 50% of equipped turtles were study-beach faithful, laying clutches on one beach, and 50% were study-beach unfaithful, nesting across 2-4 beaches on Frégate and on nearby islands. Consequently, clutch frequency estimated through tracking was 1.9 times higher than foot patrol estimates. Estimates of adult female abundance increased as the assumed proportion of clutches laid on other beaches increased, independent of clutch frequency. Across 51 studies at 43 sites around the world, study-beach unfaithful individuals were more likely to be recorded nesting at mainland beaches (21.4% compared with 9.3% on island beaches), with mainland surveys covering greater distances (1.6-1000 km) than island surveys (1-15.9 km). Maximum inter-nest distances varied across species: green turtles (Chelonia mydas; 2250 km), leatherbacks (Dermochelys coriacea; 1849 km), loggerheads (Caretta caretta; 800 km), olive ridleys (Lepidochelys olivacea; 320 km), and hawksbills (300 km). We demonstrate mixed fidelity strategies within an island hawksbill population, suggesting that fidelity reflects natal philopatry and the proximity of alternative sites. Limited monitoring coverage at remote sites likely contributes to under-detection of nestings by study-beach unfaithful individuals. Individuals using alternative sites signal behavioural plasticity that may contribute to resilience against habitat loss. We recommend characterising beach fidelity through regional data sharing and satellite tracking to inform reliable demographic inference and identify subpopulations vulnerable to climate change.
Dataset DOI: 10.5061/dryad.s7h44j1qr
Description of the data and file structure
This repository contains data used in Kale et al. (2026), in which the authors used satellite telemetry to demonstrate differences in nesting beach fidelity strategies among hawksbill turtles (Eretmochelys imbricata) in the Republic of Seychelles.
The files archived here include 1) nesting events identified using location and haul-out data, 2) distances between first and subsequent clutches recorded through tracking data, 3) clutch frequency data across years derived from beach foot patrols and tracking data, and 4) data showing whether females that laid a single clutch versus multiple clutches remigrated.
Please note that the location data have not been included in the repository to reduce the risk of exposing sensitive information about hawksbill turtles, a critically endangered species. The location data are available from the corresponding author upon reasonable request.
Files and variables
File: Data_Beach_fidelity.zip
Description: The ZIP folder contains five data files (.csv).
File: Fig1_Nesting_events.csv
Description: This file contains evidence used for validating nesting events of satellite-tracked hawksbill turtles in the Republic of Seychelles.
Number of variables: 11
Number of header rows: 1
Number of rows: 99
Variables:
- ArgosID: (character) Argos ID of the attached satellite tag
- Deployment_Date: (numeric) Date when the satellite tag was attached to a turtle (format: mm/dd/yyyy)
- Haulout_Y_N: (character) Whether the recorded point was a haul-out or a location point
- Location_Date: (numeric) Date when the data point was recorded (format: mm/dd/yyyy)
- Local_Time: (numeric) Local time in the Seychelles when the data was recorded (format: hh:mm:ss)
- Points_on_land_water: (character) Whether the location point was on land or water
- Nesting: (character) Certainty level of whether the data point represents a nesting event
- Internesting_interval_d: (numeric) Number of days elapsed between subsequent nesting events
- Location: (character) Name of the beach
- Migration_Date: (numeric) Point in time when a tracked individual began moving away from the breeding grounds (format: mm/dd/yyyy)
- Clutch_n: (numeric) Number of clutches laid post-tag attachment
Note: NAs or blank cells indicate where data were not applicable.
Data type: character, numeric
File: Fig2_OCF_ECF.csv
Description: This file contains information on the observed and estimated clutch frequency derived from foot patrol data across years (2017-2025) and satellite telemetry (2023-2024) for hawksbill turtles in the Republic of Seychelles.
Number of variables: 9
Number of header rows: 1
Number of rows: 997
Variables:
- Year: (numeric) Year when the clutches were laid
- Beach: (character) Name of the beach where the clutch was laid
- Tag_Right: (character) Serial number of metal tag attached on the right flipper
- Tag_Left: (character) Serial number of metal tag attached on the left flipper
- Date: (numeric) Date when the clutch was laid (format: mm/dd/yyyy)
- Internesting_interval_d: (numeric) Number of days elapsed between subsequent observed clutches
- OCF_n: (numeric) Observed clutch frequency (OCF) for that turtle derived from beach foot patrol data
- ECF_n: (numeric) Estimated clutch frequency (ECF) for that turtle derived from beach foot patrol data
- SatECF_n: (numeric) Estimated clutch frequency derived from satellite tracking data for instrumented turtles
Note: NAs or blank cells indicate where data were not applicable.
Data type: character, numeric
File: Fig3a_Nest_distance.csv
Description: This file contains data on the distance between the clutch recorded on satellite tag deployment day and subsequent clutches for hawksbill turtles in the Republic of Seychelles.
Number of variables: 3
Number of header rows: 1
Number of rows: 20
Variables:
- ArgosID: (character) Argos ID of the attached satellite tag
- Nest_number: (numeric) Sequential order of clutches laid after the first (satellite deployment day) nesting event
- Dist_from_nest1_km: (numeric) Straight-line distance (km) between the clutch recorded on the day satellite tag was attached and subsequent clutches
Note: NAs or blank cells indicate where data were not applicable.
Data type: character, numeric
File: Fig3b_Remigration_probab.csv
Description: This file contains data about the turtles that laid either single or multiple clutches in 2017-2018 and 2018-2019.
Number of variables: 8
Number of header rows: 1
Number of rows: 44
Variables:
- Year: (numeric) Year when the turtle was first recorded laying a clutch
- Beach: (character) Name of the study beach where the first recorded clutch was laid
- Location: (character) Section of the study beach where the first recorded clutch was laid
- Tag_Right: (character) Serial number of metal tag attached on the right flipper
- Tag_Left: (character) Serial number of metal tag attached on the left flipper
- Clutch: (character) Whether the turtle laid single clutch or multiple clutches that year
- Clutch_observed: (numeric) Total number of observed clutches the turtle laid in that year
- Status (character): Whether the tagged turtle remigrated to nest in subsequent years or nested in only a single year (one-timer)
Note: NAs or blank cells indicate where data were not applicable.
Data type: character, numeric
Code/software
Excel and R.
Study overview
We used Fastloc-GPS satellite tracking data to examine the nesting beach fidelity strategies of hawksbill turtles in the Republic of Seychelles. Using Fastloc-GPS location data and haul-out data, we identified nesting events of tracked individuals within a single nesting season (2023-2024). We further calculated the distance between the clutch recorded at the time of tag attachment and subsequent clutches of tracked individuals, showing the extent of nesting beach fidelity among different individuals.
We then compared clutch frequency estimates derived from beach foot patrol data (2017-2025) and tracking data (2023-2024), highlighting how satellite tracking can improve population parameter estimates. Additionally, we used nesting events recorded during beach foot patrols across years to determine whether individuals that laid a single clutch versus multiple clutches on the study beach remigrated in subsequent years.